Change API to remove the "Option" logic and keep only Builder. (#380)

21 files changed, 421 insertions, 877 deletions

diff --git a/api/src/main/java/io/opencensus/trace/SpanBuilder.java b/api/src/main/java/io/opencensus/trace/SpanBuilder.java
index 782248ba..f573d9a6 100644
--- a/api/src/main/java/io/opencensus/trace/SpanBuilder.java
+++ b/api/src/main/java/io/opencensus/trace/SpanBuilder.java
@@ -13,11 +13,11 @@
 
 package io.opencensus.trace;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import io.opencensus.common.NonThrowingCloseable;
 import io.opencensus.trace.base.EndSpanOptions;
 import io.opencensus.trace.base.Sampler;
-import io.opencensus.trace.base.StartSpanOptions;
-import io.opencensus.trace.internal.SpanFactory;
 import java.util.List;
 import javax.annotation.Nullable;
 
@@ -102,34 +102,15 @@ import javax.annotation.Nullable;
  * <p>If your Java version is less than Java SE 7, see {@link SpanBuilder#startSpan} and {@link
  * SpanBuilder#startScopedSpan} for usage examples.
  */
-public final class SpanBuilder {
-  private final SpanFactory spanFactory;
-  private final String name;
-  private final StartSpanOptions.Builder startSpanOptionsBuilder = StartSpanOptions.builder();
-  private Span parentSpan;
-  private SpanContext parentSpanContext;
-  private boolean remoteParent;
-
-  static SpanBuilder builder(SpanFactory spanFactory, Span parentSpan, String name) {
-    return new SpanBuilder(spanFactory, parentSpan, null, false, name);
-  }
-
-  static SpanBuilder builderWithRemoteParent(
-      SpanFactory spanFactory, SpanContext parentSpanContext, String name) {
-    return new SpanBuilder(spanFactory, null, parentSpanContext, true, name);
-  }
+public abstract class SpanBuilder {
 
   /**
-   * Sets the {@link Sampler} to use. If a {@code null} value is passed, the implementation will
-   * provide a default.
+   * Sets the {@link Sampler} to use. If not set, the implementation will provide a default.
    *
    * @param sampler The {@code Sampler} to use when determining sampling for a {@code Span}.
    * @return this.
    */
-  public SpanBuilder setSampler(@Nullable Sampler sampler) {
-    startSpanOptionsBuilder.setSampler(sampler);
-    return this;
-  }
+  public abstract SpanBuilder setSampler(Sampler sampler);
 
   /**
    * Sets the {@code List} of parent links. Links are used to link {@link Span}s in different
@@ -138,11 +119,9 @@ public final class SpanBuilder {
    *
    * @param parentLinks New links to be added.
    * @return this.
+   * @throws NullPointerException if {@code parentLinks} is {@code null}.
    */
-  public SpanBuilder setParentLinks(@Nullable List<Span> parentLinks) {
-    startSpanOptionsBuilder.setParentLinks(parentLinks);
-    return this;
-  }
+  public abstract SpanBuilder setParentLinks(List<Span> parentLinks);
 
   /**
    * Sets the option {@link Span.Options#RECORD_EVENTS} for the newly created {@code Span}. If not
@@ -151,27 +130,7 @@ public final class SpanBuilder {
    * @param recordEvents New value determining if this {@code Span} should have events recorded.
    * @return this.
    */
-  public SpanBuilder setRecordEvents(boolean recordEvents) {
-    startSpanOptionsBuilder.setRecordEvents(recordEvents);
-    return this;
-  }
-
-  /**
-   * If called this will force the newly created {@code Span} to be a root span. As a consequence,
-   * any parent specified (or inherited from the Context) will be ignored (N.B. does not apply to
-   * linked parents set through {@link #setParentLinks}).
-   *
-   * <p>This is useful when {@link Tracer#spanBuilder(String)} is used and the newly created {@code
-   * Span} needs to be decoupled from the parent {@code Span}.
-   *
-   * @return this.
-   */
-  public SpanBuilder becomeRoot() {
-    parentSpan = null;
-    parentSpanContext = null;
-    remoteParent = false;
-    return this;
-  }
+  public abstract SpanBuilder setRecordEvents(boolean recordEvents);
 
   /**
    * Starts a new {@link Span}.
@@ -201,9 +160,7 @@ public final class SpanBuilder {
    *
    * @return the newly created {@code Span}.
    */
-  public Span startSpan() {
-    return start();
-  }
+  public abstract Span startSpan();
 
   // TODO(bdrutu): Add error_prone annotation @MustBeClosed when the 2.0.16 jar is fixed.
   /**
@@ -260,28 +217,38 @@ public final class SpanBuilder {
    * @return an object that defines a scope where the newly created {@code Span} will be set to the
    *     current Context.
    */
-  public NonThrowingCloseable startScopedSpan() {
-    return new ScopedSpanHandle(start());
+  public final NonThrowingCloseable startScopedSpan() {
+    return new ScopedSpanHandle(startSpan());
   }
 
-  private SpanBuilder(
-      SpanFactory spanFactory,
-      @Nullable Span parentSpan,
-      @Nullable SpanContext parentSpanContext,
-      boolean remoteParent,
-      String name) {
-    this.parentSpan = parentSpan;
-    this.parentSpanContext = parentSpanContext;
-    this.remoteParent = remoteParent;
-    this.name = name;
-    this.spanFactory = spanFactory;
-  }
+  static final class NoopSpanBuilder extends SpanBuilder {
+    NoopSpanBuilder(@Nullable Span parentSpan, String name) {
+      checkNotNull(name, "name");
+    }
+
+    NoopSpanBuilder(SpanContext remoteParentSpanContext, String name) {
+      checkNotNull(remoteParentSpanContext, "remoteParentSpanContext");
+      checkNotNull(name, "name");
+    }
+
+    @Override
+    public Span startSpan() {
+      return BlankSpan.INSTANCE;
+    }
+
+    @Override
+    public SpanBuilder setSampler(@Nullable Sampler sampler) {
+      return this;
+    }
+
+    @Override
+    public SpanBuilder setParentLinks(List<Span> parentLinks) {
+      return this;
+    }
 
-  // Utility method to start a Span.
-  private Span start() {
-    return remoteParent
-        ? spanFactory.startSpanWithRemoteParent(
-            parentSpanContext, name, startSpanOptionsBuilder.build())
-        : spanFactory.startSpan(parentSpan, name, startSpanOptionsBuilder.build());
+    @Override
+    public SpanBuilder setRecordEvents(boolean recordEvents) {
+      return this;
+    }
   }
 }
diff --git a/api/src/main/java/io/opencensus/trace/Tracer.java b/api/src/main/java/io/opencensus/trace/Tracer.java
index e6172bed..ef5616a9 100644
--- a/api/src/main/java/io/opencensus/trace/Tracer.java
+++ b/api/src/main/java/io/opencensus/trace/Tracer.java
@@ -16,8 +16,6 @@ package io.opencensus.trace;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import io.opencensus.common.NonThrowingCloseable;
-import io.opencensus.trace.base.StartSpanOptions;
-import io.opencensus.trace.internal.SpanFactory;
 import javax.annotation.Nullable;
 
 /**
@@ -67,7 +65,6 @@ import javax.annotation.Nullable;
  */
 public abstract class Tracer {
   private static final NoopTracer noopTracer = new NoopTracer();
-  private final SpanFactory spanFactory;
 
   /**
    * Returns the no-op implementation of the {@code Tracer}.
@@ -142,7 +139,7 @@ public abstract class Tracer {
    * @param span The {@link Span} to be set to the current Context.
    * @return an object that defines a scope where the given {@link Span} will be set to the current
    *     Context.
-   * @throws NullPointerException if span is null.
+   * @throws NullPointerException if {@code span} is null.
    */
   public final NonThrowingCloseable withSpan(Span span) {
     return ContextUtils.withSpan(checkNotNull(span, "span"));
@@ -150,7 +147,7 @@ public abstract class Tracer {
 
   /**
    * Returns a {@link SpanBuilder} to create and start a new child {@link Span} as a child of to the
-   * current {@code Span} if any, otherwise create a root Span with the default options.
+   * current {@code Span} if any, otherwise creates a root {@code Span}.
    *
    * <p>See {@link SpanBuilder} for usage examples.
    *
@@ -159,7 +156,7 @@ public abstract class Tracer {
    *
    * @param name The name of the returned Span.
    * @return a {@code SpanBuilder} to create and start a new {@code Span}.
-   * @throws NullPointerException if name is null.
+   * @throws NullPointerException if {@code name} is null.
    */
   public final SpanBuilder spanBuilder(String name) {
     return spanBuilder(ContextUtils.getCurrentSpan(), name);
@@ -167,64 +164,60 @@ public abstract class Tracer {
 
   /**
    * Returns a {@link SpanBuilder} to create and start a new child {@link Span} (or root if parent
-   * is null), with parent being the designated {@code Span}.
+   * is {@code null} or has an invalid {@link SpanContext}), with parent being the designated {@code
+   * Span}.
    *
    * <p>See {@link SpanBuilder} for usage examples.
    *
-   * <p>This <b>must</b> be used to create a {@code Span} when manual Context propagation is used.
+   * <p>This <b>must</b> be used to create a {@code Span} when manual Context propagation is used
+   * OR when creating a root {@code Span} with a {@code null} parent.
    *
    * @param parent The parent of the returned Span. If null the {@code SpanBuilder} will build a
    *     root {@code Span}.
    * @param name The name of the returned Span.
    * @return a {@code SpanBuilder} to create and start a new {@code Span}.
-   * @throws NullPointerException if name is null.
+   * @throws NullPointerException if {@code name} is null.
    */
-  public final SpanBuilder spanBuilder(@Nullable Span parent, String name) {
-    return SpanBuilder.builder(spanFactory, parent, checkNotNull(name, "name"));
-  }
+  public abstract SpanBuilder spanBuilder(@Nullable Span parent, String name);
 
   /**
    * Returns a {@link SpanBuilder} to create and start a new child {@link Span} (or root if parent
-   * is null), with parent being the {@link Span} designated by the {@link SpanContext}.
+   * is an invalid {@link SpanContext}), with parent being the {@link Span} designated by the {@link
+   * SpanContext}.
    *
    * <p>See {@link SpanBuilder} for usage examples.
    *
    * <p>This <b>must</b> be used to create a {@code Span} when the parent is in a different process.
    * This is only intended for use by RPC systems or similar.
    *
-   * @param remoteParent The remote parent of the returned Span.
+   * <p>If no {@link SpanContext} OR fail to parse the {@link SpanContext} on the server side,
+   * users must call this method with an {@link SpanContext#INVALID} remote parent {@code
+   * SpanContext}.
+   *
+   * @param remoteParentSpanContext The remote parent of the returned Span.
    * @param name The name of the returned Span.
    * @return a {@code SpanBuilder} to create and start a new {@code Span}.
-   * @throws NullPointerException if name is null.
+   * @throws NullPointerException if {@code name} or {@code remoteParentSpanContext} are null.
    */
-  public final SpanBuilder spanBuilderWithRemoteParent(
-      @Nullable SpanContext remoteParent, String name) {
-    return SpanBuilder.builderWithRemoteParent(
-        spanFactory, remoteParent, checkNotNull(name, "name"));
-  }
+  public abstract SpanBuilder spanBuilderWithRemoteParent(
+      SpanContext remoteParentSpanContext, String name);
 
   // No-Op implementation of the Tracer.
   private static final class NoopTracer extends Tracer {
-    private NoopTracer() {
-      super(new NoopSpanFactory());
-    }
 
-    // No-op implementation of the SpanFactory
-    private static final class NoopSpanFactory extends SpanFactory {
-      @Override
-      public Span startSpan(@Nullable Span parent, String name, StartSpanOptions options) {
-        return BlankSpan.INSTANCE;
-      }
+    @Override
+    public SpanBuilder spanBuilder(@Nullable Span parent, String name) {
+      return new SpanBuilder.NoopSpanBuilder(parent, name);
+    }
 
-      @Override
-      public Span startSpanWithRemoteParent(
-          @Nullable SpanContext remoteParent, String name, StartSpanOptions options) {
-        return BlankSpan.INSTANCE;
-      }
+    @Override
+    public SpanBuilder spanBuilderWithRemoteParent(
+        SpanContext remoteParentSpanContext, String name) {
+      return new SpanBuilder.NoopSpanBuilder(remoteParentSpanContext, name);
     }
-  }
 
-  protected Tracer(SpanFactory spanFactory) {
-    this.spanFactory = checkNotNull(spanFactory, "spanFactory");
+    private NoopTracer() {}
   }
+
+  protected Tracer() {}
 }
diff --git a/api/src/main/java/io/opencensus/trace/base/StartSpanOptions.java b/api/src/main/java/io/opencensus/trace/base/StartSpanOptions.java
deleted file mode 100644
index 518f1e60..00000000
--- a/api/src/main/java/io/opencensus/trace/base/StartSpanOptions.java
+++ /dev/null
@@ -1,122 +0,0 @@
-/*
- * Copyright 2016, Google Inc.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *     http://www.apache.org/licenses/LICENSE-2.0
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.trace.base;
-
-import com.google.auto.value.AutoValue;
-import com.google.common.annotations.VisibleForTesting;
-import io.opencensus.trace.Span;
-import io.opencensus.trace.config.TraceConfig;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.Immutable;
-
-/**
- * A class that enables overriding the default values used when starting a {@link Span}. Allows
- * overriding the {@link Sampler sampler}, the parent links, and option to record all the events
- * even if the {@code Span} is not sampled.
- */
-@AutoValue
-@Immutable
-public abstract class StartSpanOptions {
-  private static final List<Span> EMPTY_PARENT_LINKS_LIST = Collections.emptyList();
-
-  /** The default {@code StartSpanOptions}. */
-  @VisibleForTesting public static final StartSpanOptions DEFAULT = builder().build();
-
-  /**
-   * Returns the {@link Sampler} to be used, or {@code null} if default.
-   *
-   * @return the {@code Sampler} to be used, or {@code null} if default.
-   */
-  @Nullable
-  public abstract Sampler getSampler();
-
-  /**
-   * Returns the parent links to be set for the {@link Span}.
-   *
-   * @return the parent links to be set for the {@code Span}.
-   */
-  public abstract List<Span> getParentLinks();
-
-  /**
-   * Returns the record events option, or {@code null} if default.
-   *
-   * <p>See {@link Span.Options#RECORD_EVENTS} for more details.
-   *
-   * @return the record events option, or {@code null} if default.
-   */
-  @Nullable
-  public abstract Boolean getRecordEvents();
-
-  /**
-   * Returns a new {@link Builder} with default options.
-   *
-   * @return a new {@code Builder} with default options.
-   */
-  public static Builder builder() {
-    return new AutoValue_StartSpanOptions.Builder().setParentLinks(EMPTY_PARENT_LINKS_LIST);
-  }
-
-  /** Builder class for {@link StartSpanOptions}. */
-  @AutoValue.Builder
-  public abstract static class Builder {
-
-    /**
-     * Sets the {@link Sampler} to be used. If {@code null} the default {@code Sampler} from the
-     * {@link TraceConfig#getActiveTraceParams()} will be used.
-     *
-     * @param sampler the {@link Sampler} to be used.
-     * @return this.
-     */
-    public abstract Builder setSampler(@Nullable Sampler sampler);
-
-    /**
-     * Sets the parent links to be set for the {@link Span}.
-     *
-     * @param parentLinks the parent links to be set for the {@link Span}.
-     * @return this.
-     * @throws NullPointerException if {@code parentLinks} is {@code null}.
-     */
-    public abstract Builder setParentLinks(List<Span> parentLinks);
-
-    /**
-     * Sets the record events option. If {@code null} the default value from the {@link
-     * TraceConfig#getActiveTraceParams()} will be used.
-     *
-     * <p>See {@link Span.Options#RECORD_EVENTS} for more details.
-     *
-     * @param recordEvents the record events option.
-     * @return this.
-     */
-    public abstract Builder setRecordEvents(@Nullable Boolean recordEvents);
-
-    abstract List<Span> getParentLinks(); // not public
-
-    abstract StartSpanOptions autoBuild(); // not public
-
-    /**
-     * Builds and returns a {@code StartSpanOptions} with the desired settings.
-     *
-     * @return a {@code StartSpanOptions} with the desired settings.
-     */
-    public StartSpanOptions build() {
-      setParentLinks(Collections.unmodifiableList(new ArrayList<Span>(getParentLinks())));
-      return autoBuild();
-    }
-  }
-
-  StartSpanOptions() {}
-}
diff --git a/api/src/main/java/io/opencensus/trace/internal/SpanFactory.java b/api/src/main/java/io/opencensus/trace/internal/SpanFactory.java
deleted file mode 100644
index a0306152..00000000
--- a/api/src/main/java/io/opencensus/trace/internal/SpanFactory.java
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * Copyright 2017, Google Inc.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *     http://www.apache.org/licenses/LICENSE-2.0
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.trace.internal;
-
-import io.opencensus.trace.Span;
-import io.opencensus.trace.SpanContext;
-import io.opencensus.trace.base.StartSpanOptions;
-import javax.annotation.Nullable;
-
-/** Factory class to create and start a {@link Span}. */
-public abstract class SpanFactory {
-  /**
-   * Creates and starts a new child {@link Span} (or root if parent is {@code null}), with parent
-   * being the designated {@code Span} and the given options.
-   *
-   * @param parent The parent of the returned {@code Span}.
-   * @param name The name of the returned {@code Span}.
-   * @param options The options for the start of the {@code Span}.
-   * @return A child {@code Span} that will have the name provided.
-   */
-  public abstract Span startSpan(@Nullable Span parent, String name, StartSpanOptions options);
-
-  /**
-   * Creates and starts a new child {@link Span} (or root if parent is {@code null}), with parent
-   * being the {@code Span} designated by the {@link SpanContext} and the given options.
-   *
-   * <p>This must be used to create a {@code Span} when the parent is on a different process.
-   *
-   * @param remoteParent The remote parent of the returned {@code Span}.
-   * @param name The name of the returned {@code Span}.
-   * @param options The options for the start of the {@code Span}.
-   * @return A child {@code Span} that will have the name provided.
-   */
-  public abstract Span startSpanWithRemoteParent(
-      @Nullable SpanContext remoteParent, String name, StartSpanOptions options);
-}
diff --git a/api/src/test/java/io/opencensus/trace/SpanBuilderTest.java b/api/src/test/java/io/opencensus/trace/SpanBuilderTest.java
deleted file mode 100644
index 10eccbe6..00000000
--- a/api/src/test/java/io/opencensus/trace/SpanBuilderTest.java
+++ /dev/null
@@ -1,179 +0,0 @@
-/*
- * Copyright 2017, Google Inc.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *     http://www.apache.org/licenses/LICENSE-2.0
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.trace;
-
-import static com.google.common.truth.Truth.assertThat;
-import static org.mockito.Matchers.eq;
-import static org.mockito.Matchers.isNull;
-import static org.mockito.Matchers.same;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-
-import io.opencensus.common.NonThrowingCloseable;
-import io.opencensus.trace.base.EndSpanOptions;
-import io.opencensus.trace.base.SpanId;
-import io.opencensus.trace.base.StartSpanOptions;
-import io.opencensus.trace.base.TraceId;
-import io.opencensus.trace.base.TraceOptions;
-import io.opencensus.trace.internal.SpanFactory;
-import io.opencensus.trace.samplers.Samplers;
-import java.util.Arrays;
-import java.util.List;
-import java.util.Random;
-import org.junit.Before;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-import org.mockito.Mock;
-import org.mockito.MockitoAnnotations;
-
-/** Unit tests for {@link Tracer}. */
-@RunWith(JUnit4.class)
-public class SpanBuilderTest {
-  private static final String SPAN_NAME = "MySpanName";
-  private static final Tracer tracer = Tracing.getTracer();
-  private final Random random = new Random(1234);
-  private final SpanContext spanContext =
-      SpanContext.create(
-          TraceId.generateRandomId(random), SpanId.generateRandomId(random), TraceOptions.DEFAULT);
-  @Mock private Span span;
-  @Mock private SpanFactory spanFactory;
-  private SpanBuilder spanBuilder;
-
-  @Before
-  public void setUp() {
-    MockitoAnnotations.initMocks(this);
-    spanBuilder = SpanBuilder.builder(spanFactory, BlankSpan.INSTANCE, SPAN_NAME);
-  }
-
-  @Test
-  public void startScopedSpanRoot() {
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    NonThrowingCloseable ss = spanBuilder.becomeRoot().startScopedSpan();
-    try {
-      assertThat(tracer.getCurrentSpan()).isSameAs(span);
-    } finally {
-      ss.close();
-    }
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startScopedSpanRootWithOptions() {
-    StartSpanOptions startSpanOptions =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).build();
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(startSpanOptions)))
-        .thenReturn(span);
-    NonThrowingCloseable ss =
-        spanBuilder.becomeRoot().setSampler(Samplers.neverSample()).startScopedSpan();
-    try {
-      assertThat(tracer.getCurrentSpan()).isSameAs(span);
-    } finally {
-      ss.close();
-    }
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startRootSpan() {
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span rootSpan = spanBuilder.becomeRoot().startSpan();
-    assertThat(rootSpan).isEqualTo(span);
-    rootSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startSpan_WithNullParent() {
-    spanBuilder = SpanBuilder.builder(spanFactory, null, SPAN_NAME);
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span rootSpan = spanBuilder.startSpan();
-    assertThat(rootSpan).isEqualTo(span);
-    rootSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startRootSpanWithOptions() {
-    List<Span> parentList = Arrays.<Span>asList(BlankSpan.INSTANCE);
-    StartSpanOptions startSpanOptions =
-        StartSpanOptions.builder()
-            .setSampler(Samplers.neverSample())
-            .setParentLinks(parentList)
-            .build();
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(startSpanOptions)))
-        .thenReturn(span);
-    Span rootSpan =
-        spanBuilder
-            .becomeRoot()
-            .setSampler(Samplers.neverSample())
-            .setParentLinks(parentList)
-            .startSpan();
-    assertThat(rootSpan).isEqualTo(span);
-    rootSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startChildSpan() {
-    when(spanFactory.startSpan(
-            same(BlankSpan.INSTANCE), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span childSpan = spanBuilder.startSpan();
-    assertThat(childSpan).isEqualTo(span);
-    childSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startChildSpanWithOptions() {
-    StartSpanOptions startSpanOptions =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).setRecordEvents(true).build();
-    ;
-    when(spanFactory.startSpan(same(BlankSpan.INSTANCE), same(SPAN_NAME), eq(startSpanOptions)))
-        .thenReturn(span);
-    Span childSpan =
-        spanBuilder.setSampler(Samplers.neverSample()).setRecordEvents(true).startSpan();
-    assertThat(childSpan).isEqualTo(span);
-    childSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startSpanWitRemoteParent() {
-    spanBuilder = SpanBuilder.builderWithRemoteParent(spanFactory, spanContext, SPAN_NAME);
-    when(spanFactory.startSpanWithRemoteParent(
-            same(spanContext), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span remoteChildSpan = spanBuilder.startSpan();
-    assertThat(remoteChildSpan).isEqualTo(span);
-    remoteChildSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startSpanWitRemoteParent_WithNullParent() {
-    spanBuilder = SpanBuilder.builderWithRemoteParent(spanFactory, null, SPAN_NAME);
-    when(spanFactory.startSpanWithRemoteParent(
-            isNull(SpanContext.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span remoteChildSpan = spanBuilder.startSpan();
-    assertThat(remoteChildSpan).isEqualTo(span);
-    remoteChildSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-}
diff --git a/api/src/test/java/io/opencensus/trace/TracerTest.java b/api/src/test/java/io/opencensus/trace/TracerTest.java
index 7339eae2..3c69068b 100644
--- a/api/src/test/java/io/opencensus/trace/TracerTest.java
+++ b/api/src/test/java/io/opencensus/trace/TracerTest.java
@@ -14,21 +14,11 @@
 package io.opencensus.trace;
 
 import static com.google.common.truth.Truth.assertThat;
-import static org.mockito.Matchers.eq;
-import static org.mockito.Matchers.isNull;
 import static org.mockito.Matchers.same;
-import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import io.grpc.Context;
 import io.opencensus.common.NonThrowingCloseable;
-import io.opencensus.trace.base.EndSpanOptions;
-import io.opencensus.trace.base.SpanId;
-import io.opencensus.trace.base.StartSpanOptions;
-import io.opencensus.trace.base.TraceId;
-import io.opencensus.trace.base.TraceOptions;
-import io.opencensus.trace.internal.SpanFactory;
-import java.util.Random;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -41,10 +31,11 @@ import org.mockito.MockitoAnnotations;
 /** Unit tests for {@link Tracer}. */
 @RunWith(JUnit4.class)
 public class TracerTest {
-  private static final Tracer tracer = Tracing.getTracer();
+  private static final Tracer noopTracer = Tracer.getNoopTracer();
   private static final String SPAN_NAME = "MySpanName";
   @Rule public ExpectedException thrown = ExpectedException.none();
-  @Mock private SpanFactory spanFactory;
+  @Mock private Tracer tracer;
+  @Mock private SpanBuilder spanBuilder;
   @Mock private Span span;
 
   @Before
@@ -54,163 +45,107 @@ public class TracerTest {
 
   @Test
   public void defaultGetCurrentSpan() {
-    assertThat(tracer.getCurrentSpan()).isEqualTo(BlankSpan.INSTANCE);
+    assertThat(noopTracer.getCurrentSpan()).isEqualTo(BlankSpan.INSTANCE);
   }
 
   @Test(expected = NullPointerException.class)
   public void withSpan_NullSpan() {
-    tracer.withSpan(null);
+    noopTracer.withSpan(null);
   }
 
   @Test
   public void getCurrentSpan_WithSpan() {
-    assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
-    NonThrowingCloseable ws = tracer.withSpan(span);
+    assertThat(noopTracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
+    NonThrowingCloseable ws = noopTracer.withSpan(span);
     try {
-      assertThat(tracer.getCurrentSpan()).isSameAs(span);
+      assertThat(noopTracer.getCurrentSpan()).isSameAs(span);
     } finally {
       ws.close();
     }
-    assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
+    assertThat(noopTracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
   }
 
   @Test
   public void propagationViaRunnable() {
-    Runnable runnable = null;
-    NonThrowingCloseable ws = tracer.withSpan(span);
+    Runnable runnable;
+    NonThrowingCloseable ws = noopTracer.withSpan(span);
     try {
-      assertThat(tracer.getCurrentSpan()).isSameAs(span);
+      assertThat(noopTracer.getCurrentSpan()).isSameAs(span);
       runnable =
           Context.current()
               .wrap(
                   new Runnable() {
                     @Override
                     public void run() {
-                      assertThat(tracer.getCurrentSpan()).isSameAs(span);
+                      assertThat(noopTracer.getCurrentSpan()).isSameAs(span);
                     }
                   });
     } finally {
       ws.close();
     }
-    assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
+    assertThat(noopTracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
     // When we run the runnable we will have the span in the current Context.
     runnable.run();
-    assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
+    assertThat(noopTracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
   }
 
   @Test(expected = NullPointerException.class)
   public void spanBuilderWithName_NullName() {
-    assertThat(tracer.spanBuilder(null).startSpan()).isSameAs(BlankSpan.INSTANCE);
+    noopTracer.spanBuilder(null);
   }
 
   @Test
   public void defaultSpanBuilderWithName() {
-    assertThat(tracer.spanBuilder(SPAN_NAME).startSpan()).isSameAs(BlankSpan.INSTANCE);
+    assertThat(noopTracer.spanBuilder(SPAN_NAME).startSpan()).isSameAs(BlankSpan.INSTANCE);
   }
 
   @Test(expected = NullPointerException.class)
   public void spanBuilderWithParentAndName_NullName() {
-    assertThat(tracer.spanBuilder(null, null).startSpan()).isSameAs(BlankSpan.INSTANCE);
+    noopTracer.spanBuilder(null, null);
   }
 
   @Test
   public void defaultSpanBuilderWithParentAndName() {
-    assertThat(tracer.spanBuilder(null, SPAN_NAME).startSpan()).isSameAs(BlankSpan.INSTANCE);
+    assertThat(noopTracer.spanBuilder(null, SPAN_NAME).startSpan()).isSameAs(BlankSpan.INSTANCE);
   }
 
   @Test(expected = NullPointerException.class)
   public void spanBuilderWithRemoteParent_NullName() {
-    assertThat(tracer.spanBuilderWithRemoteParent(null, null).startSpan())
-        .isSameAs(BlankSpan.INSTANCE);
+    noopTracer.spanBuilderWithRemoteParent(null, null);
+  }
+
+  @Test(expected = NullPointerException.class)
+  public void defaultSpanBuilderWitRemoteParent_NullParent() {
+    noopTracer.spanBuilderWithRemoteParent(null, SPAN_NAME);
   }
 
   @Test
-  public void defaultSpanBuilderWitRemoteParent() {
-    assertThat(tracer.spanBuilderWithRemoteParent(null, SPAN_NAME).startSpan())
+  public void defaultSpanBuilderWithRemoteParent() {
+    assertThat(noopTracer.spanBuilderWithRemoteParent(SpanContext.INVALID, SPAN_NAME).startSpan())
         .isSameAs(BlankSpan.INSTANCE);
   }
 
   @Test
-  public void startScopedSpanRoot() {
-    Tracer mockTracer = new MockTracer(spanFactory);
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    NonThrowingCloseable ss = mockTracer.spanBuilder(SPAN_NAME).becomeRoot().startScopedSpan();
+  public void startSpanWithParentFromContext() {
+    NonThrowingCloseable ws = tracer.withSpan(span);
     try {
       assertThat(tracer.getCurrentSpan()).isSameAs(span);
+      when(tracer.spanBuilder(same(span), same(SPAN_NAME))).thenReturn(spanBuilder);
+      assertThat(tracer.spanBuilder(SPAN_NAME)).isSameAs(spanBuilder);
     } finally {
-      ss.close();
+      ws.close();
     }
-    verify(span).end(same(EndSpanOptions.DEFAULT));
   }
 
   @Test
-  public void startScopedSpanChild() {
-    Tracer mockTracer = new MockTracer(spanFactory);
-    NonThrowingCloseable ws = mockTracer.withSpan(BlankSpan.INSTANCE);
+  public void startSpanWithInvalidParentFromContext() {
+    NonThrowingCloseable ws = tracer.withSpan(BlankSpan.INSTANCE);
     try {
       assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
-      when(spanFactory.startSpan(
-              same(BlankSpan.INSTANCE), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-          .thenReturn(span);
-      NonThrowingCloseable ss = mockTracer.spanBuilder(SPAN_NAME).startScopedSpan();
-      try {
-        assertThat(tracer.getCurrentSpan()).isSameAs(span);
-      } finally {
-        ss.close();
-      }
-      assertThat(tracer.getCurrentSpan()).isSameAs(BlankSpan.INSTANCE);
+      when(tracer.spanBuilder(same(BlankSpan.INSTANCE), same(SPAN_NAME))).thenReturn(spanBuilder);
+      assertThat(tracer.spanBuilder(SPAN_NAME)).isSameAs(spanBuilder);
     } finally {
       ws.close();
     }
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startRootSpan() {
-    Tracer mockTracer = new MockTracer(spanFactory);
-    when(spanFactory.startSpan(isNull(Span.class), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span rootSpan = mockTracer.spanBuilder(BlankSpan.INSTANCE, SPAN_NAME).becomeRoot().startSpan();
-    assertThat(rootSpan).isEqualTo(span);
-    rootSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startChildSpan() {
-    Tracer mockTracer = new MockTracer(spanFactory);
-    when(spanFactory.startSpan(
-            same(BlankSpan.INSTANCE), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span childSpan = mockTracer.spanBuilder(BlankSpan.INSTANCE, SPAN_NAME).startSpan();
-    assertThat(childSpan).isEqualTo(span);
-    childSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  @Test
-  public void startSpanWitRemoteParent() {
-    Random random = new Random(1234);
-    Tracer mockTracer = new MockTracer(spanFactory);
-    SpanContext spanContext =
-        SpanContext.create(
-            TraceId.generateRandomId(random),
-            SpanId.generateRandomId(random),
-            TraceOptions.DEFAULT);
-    when(spanFactory.startSpanWithRemoteParent(
-            same(spanContext), same(SPAN_NAME), eq(StartSpanOptions.DEFAULT)))
-        .thenReturn(span);
-    Span remoteChildSpan =
-        mockTracer.spanBuilderWithRemoteParent(spanContext, SPAN_NAME).startSpan();
-    assertThat(remoteChildSpan).isEqualTo(span);
-    remoteChildSpan.end();
-    verify(span).end(same(EndSpanOptions.DEFAULT));
-  }
-
-  private static final class MockTracer extends Tracer {
-    private MockTracer(SpanFactory spanFactory) {
-      super(spanFactory);
-    }
   }
 }
diff --git a/api/src/test/java/io/opencensus/trace/base/StartSpanOptionsTest.java b/api/src/test/java/io/opencensus/trace/base/StartSpanOptionsTest.java
deleted file mode 100644
index 1a983b73..00000000
--- a/api/src/test/java/io/opencensus/trace/base/StartSpanOptionsTest.java
+++ /dev/null
@@ -1,114 +0,0 @@
-/*
- * Copyright 2017, Google Inc.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *     http://www.apache.org/licenses/LICENSE-2.0
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.trace.base;
-
-import static com.google.common.truth.Truth.assertThat;
-
-import com.google.common.testing.EqualsTester;
-import io.opencensus.trace.BlankSpan;
-import io.opencensus.trace.Span;
-import io.opencensus.trace.samplers.Samplers;
-import java.util.Arrays;
-import java.util.LinkedList;
-import java.util.List;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-
-/** Unit tests for {@link StartSpanOptions}. */
-@RunWith(JUnit4.class)
-public class StartSpanOptionsTest {
-  private final List<Span> singleParentList = Arrays.<Span>asList(BlankSpan.INSTANCE);
-
-  @Test
-  public void defaultOptions() {
-    StartSpanOptions defaultOptions = StartSpanOptions.builder().build();
-    assertThat(defaultOptions.getSampler()).isNull();
-    assertThat(defaultOptions.getParentLinks().isEmpty()).isTrue();
-    assertThat(defaultOptions.getRecordEvents()).isNull();
-  }
-
-  @Test
-  public void setSampler() {
-    StartSpanOptions options =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).build();
-    assertThat(options.getSampler()).isEqualTo(Samplers.neverSample());
-    assertThat(options.getParentLinks().isEmpty()).isTrue();
-    assertThat(options.getRecordEvents()).isNull();
-  }
-
-  @Test
-  public void setParentLinks() {
-    StartSpanOptions options = StartSpanOptions.builder().setParentLinks(singleParentList).build();
-    assertThat(options.getSampler()).isNull();
-    assertThat(options.getParentLinks()).isEqualTo(singleParentList);
-    assertThat(options.getRecordEvents()).isNull();
-  }
-
-  @Test
-  public void setParentLinks_EmptyList() {
-    StartSpanOptions options =
-        StartSpanOptions.builder().setParentLinks(new LinkedList<Span>()).build();
-    assertThat(options.getSampler()).isNull();
-    assertThat(options.getParentLinks().size()).isEqualTo(0);
-    assertThat(options.getRecordEvents()).isNull();
-  }
-
-  @Test
-  public void setParentLinks_MultipleParents() {
-    StartSpanOptions options =
-        StartSpanOptions.builder()
-            .setParentLinks(Arrays.<Span>asList(BlankSpan.INSTANCE, BlankSpan.INSTANCE))
-            .build();
-    assertThat(options.getSampler()).isNull();
-    assertThat(options.getParentLinks().size()).isEqualTo(2);
-    assertThat(options.getRecordEvents()).isNull();
-  }
-
-  @Test
-  public void setRecordEvents() {
-    StartSpanOptions options = StartSpanOptions.builder().setRecordEvents(true).build();
-    assertThat(options.getSampler()).isNull();
-    assertThat(options.getParentLinks().isEmpty()).isTrue();
-    assertThat(options.getRecordEvents()).isTrue();
-  }
-
-  @Test
-  public void setAllProperties() {
-    StartSpanOptions options =
-        StartSpanOptions.builder()
-            .setSampler(Samplers.alwaysSample())
-            .setRecordEvents(true)
-            .setParentLinks(singleParentList)
-            .build();
-    assertThat(options.getSampler()).isEqualTo(Samplers.alwaysSample());
-    assertThat(options.getParentLinks()).isEqualTo(singleParentList);
-    assertThat(options.getRecordEvents()).isTrue();
-  }
-
-  @Test
-  public void startSpanOptions_EqualsAndHashCode() {
-    EqualsTester tester = new EqualsTester();
-    StartSpanOptions optionsWithAlwaysSampler1 =
-        StartSpanOptions.builder().setSampler(Samplers.alwaysSample()).build();
-    StartSpanOptions optionsWithAlwaysSampler2 =
-        StartSpanOptions.builder().setSampler(Samplers.alwaysSample()).build();
-    tester.addEqualityGroup(optionsWithAlwaysSampler1, optionsWithAlwaysSampler2);
-    StartSpanOptions optionsWithNeverSampler =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).build();
-    tester.addEqualityGroup(optionsWithNeverSampler);
-    tester.addEqualityGroup(StartSpanOptions.DEFAULT);
-    tester.testEquals();
-  }
-}
diff --git a/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsNonSampledSpanBenchmark.java b/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsNonSampledSpanBenchmark.java
index 3013e764..06a1412f 100644
--- a/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsNonSampledSpanBenchmark.java
+++ b/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsNonSampledSpanBenchmark.java
@@ -36,9 +36,9 @@ public class RecordTraceEventsNonSampledSpanBenchmark {
   private static final String ATTRIBUTE_KEY = "MyAttributeKey";
   private static final String ATTRIBUTE_VALUE = "MyAttributeValue";
   private Span linkedSpan =
-      tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.neverSample()).startSpan();
+      tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.neverSample()).startSpan();
   private Span span =
-      tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.neverSample()).startSpan();
+      tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.neverSample()).startSpan();
 
   /** TearDown method. */
   @TearDown
diff --git a/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsSampledSpanBenchmark.java b/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsSampledSpanBenchmark.java
index ccfbc775..5773923f 100644
--- a/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsSampledSpanBenchmark.java
+++ b/benchmarks/src/jmh/java/io/opencensus/trace/RecordTraceEventsSampledSpanBenchmark.java
@@ -36,9 +36,9 @@ public class RecordTraceEventsSampledSpanBenchmark {
   private static final String ATTRIBUTE_KEY = "MyAttributeKey";
   private static final String ATTRIBUTE_VALUE = "MyAttributeValue";
   private Span linkedSpan =
-      tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.alwaysSample()).startSpan();
+      tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.alwaysSample()).startSpan();
   private Span span =
-      tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.alwaysSample()).startSpan();
+      tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.alwaysSample()).startSpan();
 
   /** TearDown method. */
   @TearDown
diff --git a/benchmarks/src/jmh/java/io/opencensus/trace/StartEndSpanBenchmark.java b/benchmarks/src/jmh/java/io/opencensus/trace/StartEndSpanBenchmark.java
index 0a86b6f8..8418184f 100644
--- a/benchmarks/src/jmh/java/io/opencensus/trace/StartEndSpanBenchmark.java
+++ b/benchmarks/src/jmh/java/io/opencensus/trace/StartEndSpanBenchmark.java
@@ -23,13 +23,13 @@ import org.openjdk.jmh.annotations.Scope;
 import org.openjdk.jmh.annotations.State;
 import org.openjdk.jmh.annotations.TearDown;
 
-/** Benchmarks for {@link SpanFactoryImpl} and {@link SpanImpl}. */
+/** Benchmarks for {@link SpanBuilderImpl} and {@link SpanImpl}. */
 @State(Scope.Benchmark)
 public class StartEndSpanBenchmark {
   private static final Tracer tracer = Tracing.getTracer();
   private static final String SPAN_NAME = "MySpanName";
   private Span rootSpan =
-      tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.neverSample()).startSpan();
+      tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.neverSample()).startSpan();
 
   @TearDown
   public void doTearDown() {
@@ -45,7 +45,7 @@ public class StartEndSpanBenchmark {
   @OutputTimeUnit(TimeUnit.NANOSECONDS)
   public Span startEndNonSampledRootSpan() {
     Span span =
-        tracer.spanBuilder(SPAN_NAME).becomeRoot().setSampler(Samplers.neverSample()).startSpan();
+        tracer.spanBuilder(null, SPAN_NAME).setSampler(Samplers.neverSample()).startSpan();
     span.end();
     return span;
   }
@@ -60,8 +60,7 @@ public class StartEndSpanBenchmark {
   public Span startEndRecordEventsRootSpan() {
     Span span =
         tracer
-            .spanBuilder(SPAN_NAME)
-            .becomeRoot()
+            .spanBuilder(null, SPAN_NAME)
             .setSampler(Samplers.neverSample())
             .setRecordEvents(true)
             .startSpan();
diff --git a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
index aa23f3f7..c6fa0317 100644
--- a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
+++ b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansContextTracing.java
@@ -49,7 +49,7 @@ public final class MultiSpansContextTracing {
   /** Main method. */
   public static void main(String[] args) {
     LoggingHandler.register(Tracing.getExportComponent().getSpanExporter());
-    Span span = tracer.spanBuilder("MyRootSpan").becomeRoot().startSpan();
+    Span span = tracer.spanBuilder(null,"MyRootSpan").startSpan();
     try (NonThrowingCloseable ws = tracer.withSpan(span)) {
       doWork();
     }
diff --git a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
index 10f2d2ca..547403bb 100644
--- a/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
+++ b/examples/src/main/java/io/opencensus/examples/trace/MultiSpansScopedTracing.java
@@ -48,7 +48,7 @@ public final class MultiSpansScopedTracing {
   public static void main(String[] args) {
     LoggingHandler.register(Tracing.getExportComponent().getSpanExporter());
     try (NonThrowingCloseable ss =
-        tracer.spanBuilder("MyRootSpan").becomeRoot().startScopedSpan()) {
+        tracer.spanBuilder(null,"MyRootSpan").startScopedSpan()) {
       doWork();
     }
   }
diff --git a/impl_core/src/main/java/io/opencensus/trace/SpanBuilderImpl.java b/impl_core/src/main/java/io/opencensus/trace/SpanBuilderImpl.java
new file mode 100644
index 00000000..74a4ae34
--- /dev/null
+++ b/impl_core/src/main/java/io/opencensus/trace/SpanBuilderImpl.java
@@ -0,0 +1,192 @@
+/*
+ * Copyright 2017, Google Inc.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.trace;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import io.opencensus.common.Clock;
+import io.opencensus.internal.TimestampConverter;
+import io.opencensus.trace.base.Link;
+import io.opencensus.trace.base.Link.Type;
+import io.opencensus.trace.base.Sampler;
+import io.opencensus.trace.base.SpanId;
+import io.opencensus.trace.base.TraceId;
+import io.opencensus.trace.base.TraceOptions;
+import io.opencensus.trace.config.TraceConfig;
+import io.opencensus.trace.config.TraceParams;
+import io.opencensus.trace.internal.RandomHandler;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Random;
+import javax.annotation.Nullable;
+
+/** Implementation of the {@link SpanBuilder}. */
+final class SpanBuilderImpl extends SpanBuilder {
+  private final Options options;
+
+  private final String name;
+  private final Span parentSpan;
+  private final SpanContext remoteParentSpanContext;
+  private Sampler sampler;
+  private List<Span> parentLinks = Collections.<Span>emptyList();
+  private Boolean recordEvents;
+
+  private Span startSpanInternal(
+      @Nullable SpanContext parent,
+      boolean hasRemoteParent,
+      String name,
+      Sampler sampler,
+      List<Span> parentLinks,
+      Boolean recordEvents,
+      @Nullable TimestampConverter timestampConverter) {
+    TraceParams activeTraceParams = options.traceConfig.getActiveTraceParams();
+    Random random = options.randomHandler.current();
+    TraceId traceId;
+    SpanId spanId = SpanId.generateRandomId(random);
+    SpanId parentSpanId = null;
+    TraceOptions.Builder traceOptionsBuilder;
+    if (parent == null || !parent.isValid()) {
+      // New root span.
+      traceId = TraceId.generateRandomId(random);
+      traceOptionsBuilder = TraceOptions.builder();
+      // This is a root span so no remote or local parent.
+      hasRemoteParent = false;
+    } else {
+      // New child span.
+      traceId = parent.getTraceId();
+      parentSpanId = parent.getSpanId();
+      traceOptionsBuilder = TraceOptions.builder(parent.getTraceOptions());
+    }
+    if (sampler == null) {
+      sampler = activeTraceParams.getSampler();
+    }
+    if (sampler.shouldSample(parent, hasRemoteParent, traceId, spanId, name, parentLinks)) {
+      traceOptionsBuilder.setIsSampled();
+    }
+    TraceOptions traceOptions = traceOptionsBuilder.build();
+    EnumSet<Span.Options> spanOptions = EnumSet.noneOf(Span.Options.class);
+    if (traceOptions.isSampled() || Boolean.TRUE.equals(recordEvents)) {
+      spanOptions.add(Span.Options.RECORD_EVENTS);
+    }
+    Span span =
+        SpanImpl.startSpan(
+            SpanContext.create(traceId, spanId, traceOptions),
+            spanOptions,
+            name,
+            parentSpanId,
+            hasRemoteParent,
+            activeTraceParams,
+            options.startEndHandler,
+            timestampConverter,
+            options.clock);
+    linkSpans(span, parentLinks);
+    return span;
+  }
+
+  private static void linkSpans(Span span, List<Span> parentLinks) {
+    if (!parentLinks.isEmpty()) {
+      Link childLink = Link.fromSpanContext(span.getContext(), Type.CHILD);
+      for (Span linkedSpan : parentLinks) {
+        linkedSpan.addLink(childLink);
+        span.addLink(Link.fromSpanContext(linkedSpan.getContext(), Type.PARENT));
+      }
+    }
+  }
+
+  static SpanBuilder createBuilder(@Nullable Span parentSpan, String name, Options options) {
+    return new SpanBuilderImpl(parentSpan, null, name, options);
+  }
+
+  static SpanBuilder createBuilderWithRemoteParent(
+      SpanContext remoteParentSpanContext, String name, Options options) {
+    return new SpanBuilderImpl(null, checkNotNull(remoteParentSpanContext,
+        "remoteParentSpanContext"), name, options);
+  }
+
+  private SpanBuilderImpl(
+      @Nullable Span parentSpan,
+      @Nullable SpanContext remoteParentSpanContext,
+      String name,
+      Options options) {
+    this.name = checkNotNull(name, "name");
+    this.parentSpan = parentSpan;
+    this.remoteParentSpanContext = remoteParentSpanContext;
+    this.options = options;
+  }
+
+  @Override
+  public Span startSpan() {
+    SpanContext parentContext = remoteParentSpanContext;
+    boolean hasRemoteParent = parentContext != null;
+    TimestampConverter timestampConverter = null;
+    if (!hasRemoteParent) {
+      // This is not a child of a remote Span. Get the parent SpanContext from the parent Span if
+      // any.
+      Span parent = parentSpan;
+      if (parent != null) {
+        parentContext = parent.getContext();
+        // Pass the timestamp converter from the parent to ensure that the recorded events are in
+        // the right order. Implementation uses System.nanoTime() which is monotonically increasing.
+        if (parent instanceof SpanImpl) {
+          timestampConverter = ((SpanImpl) parent).getTimestampConverter();
+        }
+      }
+    }
+    return startSpanInternal(
+        parentContext,
+        hasRemoteParent,
+        name,
+        sampler,
+        parentLinks,
+        recordEvents,
+        timestampConverter);
+  }
+
+  static final class Options {
+    private final RandomHandler randomHandler;
+    private final SpanImpl.StartEndHandler startEndHandler;
+    private final Clock clock;
+    private final TraceConfig traceConfig;
+
+    Options(
+        RandomHandler randomHandler,
+        SpanImpl.StartEndHandler startEndHandler,
+        Clock clock,
+        TraceConfig traceConfig) {
+      this.randomHandler = checkNotNull(randomHandler, "randomHandler");
+      this.startEndHandler = checkNotNull(startEndHandler, "startEndHandler");
+      this.clock = checkNotNull(clock, "clock");
+      this.traceConfig = checkNotNull(traceConfig, "traceConfig");
+    }
+  }
+
+  @Override
+  public SpanBuilder setSampler(Sampler sampler) {
+    this.sampler = checkNotNull(sampler, "sampler");
+    return this;
+  }
+
+  @Override
+  public SpanBuilder setParentLinks(List<Span> parentLinks) {
+    this.parentLinks = checkNotNull(parentLinks, "parentLinks");
+    return this;
+  }
+
+  @Override
+  public SpanBuilder setRecordEvents(boolean recordEvents) {
+    this.recordEvents = recordEvents;
+    return this;
+  }
+}
diff --git a/impl_core/src/main/java/io/opencensus/trace/SpanFactoryImpl.java b/impl_core/src/main/java/io/opencensus/trace/SpanFactoryImpl.java
deleted file mode 100644
index 4e816d97..00000000
--- a/impl_core/src/main/java/io/opencensus/trace/SpanFactoryImpl.java
+++ /dev/null
@@ -1,137 +0,0 @@
-/*
- * Copyright 2017, Google Inc.
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *     http://www.apache.org/licenses/LICENSE-2.0
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.opencensus.trace;
-
-import static com.google.common.base.Preconditions.checkNotNull;
-
-import io.opencensus.common.Clock;
-import io.opencensus.internal.TimestampConverter;
-import io.opencensus.trace.Span.Options;
-import io.opencensus.trace.base.Link;
-import io.opencensus.trace.base.Link.Type;
-import io.opencensus.trace.base.Sampler;
-import io.opencensus.trace.base.SpanId;
-import io.opencensus.trace.base.StartSpanOptions;
-import io.opencensus.trace.base.TraceId;
-import io.opencensus.trace.base.TraceOptions;
-import io.opencensus.trace.config.TraceConfig;
-import io.opencensus.trace.config.TraceParams;
-import io.opencensus.trace.internal.RandomHandler;
-import io.opencensus.trace.internal.SpanFactory;
-import java.util.EnumSet;
-import java.util.List;
-import java.util.Random;
-import javax.annotation.Nullable;
-
-/** Implementation of the {@link SpanFactory}. */
-final class SpanFactoryImpl extends SpanFactory {
-  private final RandomHandler randomHandler;
-  private final SpanImpl.StartEndHandler startEndHandler;
-  private final Clock clock;
-  private final TraceConfig traceConfig;
-
-  @Override
-  public Span startSpan(@Nullable Span parent, String name, StartSpanOptions options) {
-    SpanContext parentContext = null;
-    TimestampConverter timestampConverter = null;
-    if (parent != null) {
-      parentContext = parent.getContext();
-      // Pass the timestamp converter from the parent to ensure that the recorded events are in
-      // the right order. Implementation uses System.nanoTime() which is monotonically increasing.
-      if (parent instanceof SpanImpl) {
-        timestampConverter = ((SpanImpl) parent).getTimestampConverter();
-      }
-    }
-    return startSpanInternal(parentContext, false, name, options, timestampConverter);
-  }
-
-  @Override
-  public Span startSpanWithRemoteParent(
-      @Nullable SpanContext remoteParent, String name, StartSpanOptions options) {
-    return startSpanInternal(remoteParent, true, name, options, null);
-  }
-
-  Span startSpanInternal(
-      @Nullable SpanContext parent,
-      boolean hasRemoteParent,
-      String name,
-      StartSpanOptions startSpanOptions,
-      @Nullable TimestampConverter timestampConverter) {
-    TraceParams activeTraceParams = traceConfig.getActiveTraceParams();
-    Random random = randomHandler.current();
-    TraceId traceId;
-    SpanId spanId = SpanId.generateRandomId(random);
-    SpanId parentSpanId = null;
-    TraceOptions.Builder traceOptionsBuilder;
-    if (parent == null || !parent.isValid()) {
-      // New root span.
-      traceId = TraceId.generateRandomId(random);
-      traceOptionsBuilder = TraceOptions.builder();
-      // This is a root span so no remote or local parent.
-      hasRemoteParent = false;
-    } else {
-      // New child span.
-      traceId = parent.getTraceId();
-      parentSpanId = parent.getSpanId();
-      traceOptionsBuilder = TraceOptions.builder(parent.getTraceOptions());
-    }
-    Sampler sampler =
-        startSpanOptions.getSampler() != null
-            ? startSpanOptions.getSampler()
-            : activeTraceParams.getSampler();
-    if (sampler.shouldSample(
-        parent, hasRemoteParent, traceId, spanId, name, startSpanOptions.getParentLinks())) {
-      traceOptionsBuilder.setIsSampled();
-    }
-    TraceOptions traceOptions = traceOptionsBuilder.build();
-    EnumSet<Options> spanOptions = EnumSet.noneOf(Options.class);
-    if (traceOptions.isSampled() || Boolean.TRUE.equals(startSpanOptions.getRecordEvents())) {
-      spanOptions.add(Options.RECORD_EVENTS);
-    }
-    Span span =
-        SpanImpl.startSpan(
-            SpanContext.create(traceId, spanId, traceOptions),
-            spanOptions,
-            name,
-            parentSpanId,
-            hasRemoteParent,
-            activeTraceParams,
-            startEndHandler,
-            timestampConverter,
-            clock);
-    linkSpans(span, startSpanOptions.getParentLinks());
-    return span;
-  }
-
-  private static void linkSpans(Span span, List<Span> parentLinks) {
-    if (!parentLinks.isEmpty()) {
-      Link childLink = Link.fromSpanContext(span.getContext(), Type.CHILD);
-      for (Span linkedSpan : parentLinks) {
-        linkedSpan.addLink(childLink);
-        span.addLink(Link.fromSpanContext(linkedSpan.getContext(), Type.PARENT));
-      }
-    }
-  }
-
-  SpanFactoryImpl(
-      RandomHandler randomHandler,
-      SpanImpl.StartEndHandler startEndHandler,
-      Clock clock,
-      TraceConfig traceConfig) {
-    this.randomHandler = checkNotNull(randomHandler, "randomHandler");
-    this.startEndHandler = checkNotNull(startEndHandler, "startEndHandler");
-    this.clock = checkNotNull(clock, "clock");
-    this.traceConfig = checkNotNull(traceConfig, "traceConfig");
-  }
-}
diff --git a/impl_core/src/main/java/io/opencensus/trace/StartEndHandlerImpl.java b/impl_core/src/main/java/io/opencensus/trace/StartEndHandlerImpl.java
index b0f7e07a..9159eead 100644
--- a/impl_core/src/main/java/io/opencensus/trace/StartEndHandlerImpl.java
+++ b/impl_core/src/main/java/io/opencensus/trace/StartEndHandlerImpl.java
@@ -68,8 +68,7 @@ public final class StartEndHandlerImpl implements StartEndHandler {
   public void onEnd(SpanImpl span) {
     if ((span.getOptions().contains(Options.RECORD_EVENTS) && enqueueEventForNonSampledSpans)
         || span.getContext().getTraceOptions().isSampled()) {
-      eventQueue.enqueue(
-          new SpanEndEvent(span, spanExporter, runningSpanStore, sampledSpanStore));
+      eventQueue.enqueue(new SpanEndEvent(span, spanExporter, runningSpanStore, sampledSpanStore));
     }
   }
 
diff --git a/impl_core/src/main/java/io/opencensus/trace/TracerImpl.java b/impl_core/src/main/java/io/opencensus/trace/TracerImpl.java
index f753a847..b15a8b99 100644
--- a/impl_core/src/main/java/io/opencensus/trace/TracerImpl.java
+++ b/impl_core/src/main/java/io/opencensus/trace/TracerImpl.java
@@ -16,14 +16,30 @@ package io.opencensus.trace;
 import io.opencensus.common.Clock;
 import io.opencensus.trace.config.TraceConfig;
 import io.opencensus.trace.internal.RandomHandler;
+import javax.annotation.Nullable;
 
 /** Implementation of the {@link Tracer}. */
 final class TracerImpl extends Tracer {
+  private final SpanBuilderImpl.Options spanBuilderOptions;
+
   TracerImpl(
       RandomHandler randomHandler,
       SpanImpl.StartEndHandler startEndHandler,
       Clock clock,
       TraceConfig traceConfig) {
-    super(new SpanFactoryImpl(randomHandler, startEndHandler, clock, traceConfig));
+    spanBuilderOptions =
+        new SpanBuilderImpl.Options(randomHandler, startEndHandler, clock, traceConfig);
+  }
+
+  @Override
+  public SpanBuilder spanBuilder(@Nullable Span parent, String name) {
+    return SpanBuilderImpl.createBuilder(parent, name, spanBuilderOptions);
+  }
+
+  @Override
+  public SpanBuilder spanBuilderWithRemoteParent(
+      SpanContext remoteParentSpanContext, String name) {
+    return SpanBuilderImpl.createBuilderWithRemoteParent(
+        remoteParentSpanContext, name, spanBuilderOptions);
   }
 }
diff --git a/impl_core/src/main/java/io/opencensus/trace/export/ExportComponentImpl.java b/impl_core/src/main/java/io/opencensus/trace/export/ExportComponentImpl.java
index a6b80986..fa968f4e 100644
--- a/impl_core/src/main/java/io/opencensus/trace/export/ExportComponentImpl.java
+++ b/impl_core/src/main/java/io/opencensus/trace/export/ExportComponentImpl.java
@@ -43,8 +43,8 @@ public final class ExportComponentImpl extends ExportComponent {
   }
 
   /**
-   * Returns a new {@code ExportComponentImpl} that has valid instances for {@link
-   * RunningSpanStore} and {@link SampledSpanStore}.
+   * Returns a new {@code ExportComponentImpl} that has valid instances for {@link RunningSpanStore}
+   * and {@link SampledSpanStore}.
    *
    * @return a new {@code ExportComponentImpl}.
    */
@@ -65,8 +65,8 @@ public final class ExportComponentImpl extends ExportComponent {
   /**
    * Constructs a new {@code ExportComponentImpl}.
    *
-   * @param supportInProcessStores {@code true} to instantiate {@link RunningSpanStore} and
-   *     {@link SampledSpanStore}.
+   * @param supportInProcessStores {@code true} to instantiate {@link RunningSpanStore} and {@link
+   *     SampledSpanStore}.
    */
   private ExportComponentImpl(boolean supportInProcessStores) {
     this.spanExporter = SpanExporterImpl.create(EXPORTER_BUFFER_SIZE, EXPORTER_SCHEDULE_DELAY_MS);
diff --git a/impl_core/src/main/java/io/opencensus/trace/export/SampledSpanStoreImpl.java b/impl_core/src/main/java/io/opencensus/trace/export/SampledSpanStoreImpl.java
index a2a986e5..b9a62e00 100644
--- a/impl_core/src/main/java/io/opencensus/trace/export/SampledSpanStoreImpl.java
+++ b/impl_core/src/main/java/io/opencensus/trace/export/SampledSpanStoreImpl.java
@@ -40,6 +40,7 @@ public final class SampledSpanStoreImpl extends SampledSpanStore {
   private static final int MAX_PER_SPAN_NAME_SAMPLES =
       NUM_SAMPLES_PER_LATENCY_BUCKET * NUM_LATENCY_BUCKETS
           + NUM_SAMPLES_PER_ERROR_BUCKET * NUM_ERROR_BUCKETS;
+
   @GuardedBy("samples")
   private final Map<String, PerSpanNameSamples> samples;
 
@@ -91,8 +92,8 @@ public final class SampledSpanStoreImpl extends SampledSpanStore {
   }
 
   /**
-   * Keeps samples for a given span name. Samples for all the latency buckets and for all
-   * canonical codes other than OK.
+   * Keeps samples for a given span name. Samples for all the latency buckets and for all canonical
+   * codes other than OK.
    */
   private static final class PerSpanNameSamples {
 
@@ -210,8 +211,8 @@ public final class SampledSpanStoreImpl extends SampledSpanStore {
   }
 
   /**
-   * Considers to save the given spans to the stored samples. This must be called at the end of
-   * each Span with the option RECORD_EVENTS.
+   * Considers to save the given spans to the stored samples. This must be called at the end of each
+   * Span with the option RECORD_EVENTS.
    *
    * @param span the span to be consider for storing into the store buckets.
    */
diff --git a/impl_core/src/main/java/io/opencensus/trace/internal/RandomHandler.java b/impl_core/src/main/java/io/opencensus/trace/internal/RandomHandler.java
index 602a0acc..d04d0052 100644
--- a/impl_core/src/main/java/io/opencensus/trace/internal/RandomHandler.java
+++ b/impl_core/src/main/java/io/opencensus/trace/internal/RandomHandler.java
@@ -31,16 +31,12 @@ public abstract class RandomHandler {
    */
   public abstract Random current();
 
-  /**
-   * Implementation of the {@link RandomHandler} using {@link SecureRandom}.
-   */
+  /** Implementation of the {@link RandomHandler} using {@link SecureRandom}. */
   @ThreadSafe
   public static final class SecureRandomHandler extends RandomHandler {
     private final Random random = new SecureRandom();
 
-    /**
-     * Constructs a new {@link SecureRandomHandler}.
-     */
+    /** Constructs a new {@link SecureRandomHandler}. */
     public SecureRandomHandler() {}
 
     @Override
diff --git a/impl_core/src/test/java/io/opencensus/trace/SpanFactoryImplTest.java b/impl_core/src/test/java/io/opencensus/trace/SpanBuilderImplTest.java
index 1d5cf3ac..afcd3b8b 100644
--- a/impl_core/src/test/java/io/opencensus/trace/SpanFactoryImplTest.java
+++ b/impl_core/src/test/java/io/opencensus/trace/SpanBuilderImplTest.java
@@ -20,7 +20,6 @@ import io.opencensus.testing.common.TestClock;
 import io.opencensus.trace.Span.Options;
 import io.opencensus.trace.SpanImpl.StartEndHandler;
 import io.opencensus.trace.base.SpanId;
-import io.opencensus.trace.base.StartSpanOptions;
 import io.opencensus.trace.base.TraceId;
 import io.opencensus.trace.base.TraceOptions;
 import io.opencensus.trace.config.TraceConfig;
@@ -36,11 +35,11 @@ import org.junit.runners.JUnit4;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
-/** Unit tests for {@link SpanFactoryImpl}. */
+/** Unit tests for {@link SpanBuilderImpl}. */
 @RunWith(JUnit4.class)
-public class SpanFactoryImplTest {
+public class SpanBuilderImplTest {
   private static final String SPAN_NAME = "MySpanName";
-  private SpanFactoryImpl spanFactory;
+  private SpanBuilderImpl.Options spanBuilderOptions;
   private TraceParams alwaysSampleTraceParams =
       TraceParams.DEFAULT.toBuilder().setSampler(Samplers.alwaysSample()).build();
   private final TestClock testClock = TestClock.create();
@@ -51,14 +50,14 @@ public class SpanFactoryImplTest {
   @Before
   public void setUp() {
     MockitoAnnotations.initMocks(this);
-    spanFactory = new SpanFactoryImpl(randomHandler, startEndHandler, testClock, traceConfig);
+    spanBuilderOptions =
+        new SpanBuilderImpl.Options(randomHandler, startEndHandler, testClock, traceConfig);
+    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
   }
 
   @Test
   public void startSpanNullParent() {
-    StartSpanOptions startSpanOptions = StartSpanOptions.DEFAULT;
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span span = spanFactory.startSpan(null, SPAN_NAME, startSpanOptions);
+    Span span = SpanBuilderImpl.createBuilder(null, SPAN_NAME, spanBuilderOptions).startSpan();
     assertThat(span.getContext().isValid()).isTrue();
     assertThat(span.getOptions().contains(Options.RECORD_EVENTS)).isTrue();
     assertThat(span.getContext().getTraceOptions().isSampled()).isTrue();
@@ -72,10 +71,11 @@ public class SpanFactoryImplTest {
 
   @Test
   public void startSpanNullParentWithRecordEvents() {
-    StartSpanOptions startSpanOptions =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).setRecordEvents(true).build();
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span span = spanFactory.startSpan(null, SPAN_NAME, startSpanOptions);
+    Span span =
+        SpanBuilderImpl.createBuilder(null, SPAN_NAME, spanBuilderOptions)
+            .setSampler(Samplers.neverSample())
+            .setRecordEvents(true)
+            .startSpan();
     assertThat(span.getContext().isValid()).isTrue();
     assertThat(span.getOptions().contains(Options.RECORD_EVENTS)).isTrue();
     assertThat(span.getContext().getTraceOptions().isSampled()).isFalse();
@@ -87,38 +87,23 @@ public class SpanFactoryImplTest {
 
   @Test
   public void startSpanNullParentNoRecordOptions() {
-    StartSpanOptions startSpanOptions =
-        StartSpanOptions.builder().setSampler(Samplers.neverSample()).build();
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span span = spanFactory.startSpan(null, SPAN_NAME, startSpanOptions);
+    Span span =
+        SpanBuilderImpl.createBuilder(null, SPAN_NAME, spanBuilderOptions)
+            .setSampler(Samplers.neverSample())
+            .startSpan();
     assertThat(span.getContext().isValid()).isTrue();
     assertThat(span.getOptions().contains(Options.RECORD_EVENTS)).isFalse();
     assertThat(span.getContext().getTraceOptions().isSampled()).isFalse();
   }
 
   @Test
-  public void startRemoteSpanNullParent() {
-    StartSpanOptions startSpanOptions = StartSpanOptions.DEFAULT;
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span span = spanFactory.startSpanWithRemoteParent(null, SPAN_NAME, startSpanOptions);
-    assertThat(span.getContext().isValid()).isTrue();
-    assertThat(span.getOptions().contains(Options.RECORD_EVENTS)).isTrue();
-    assertThat(span.getContext().getTraceOptions().isSampled()).isTrue();
-    assertThat(span instanceof SpanImpl).isTrue();
-    SpanData spanData = ((SpanImpl) span).toSpanData();
-    assertThat(spanData.getParentSpanId()).isNull();
-    assertThat(spanData.getHasRemoteParent()).isFalse();
-  }
-
-  @Test
   public void startChildSpan() {
-    StartSpanOptions startSpanOptions = StartSpanOptions.DEFAULT;
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span rootSpan = spanFactory.startSpan(null, SPAN_NAME, startSpanOptions);
+    Span rootSpan = SpanBuilderImpl.createBuilder(null, SPAN_NAME, spanBuilderOptions).startSpan();
     assertThat(rootSpan.getContext().isValid()).isTrue();
     assertThat(rootSpan.getOptions().contains(Options.RECORD_EVENTS)).isTrue();
     assertThat(rootSpan.getContext().getTraceOptions().isSampled()).isTrue();
-    Span childSpan = spanFactory.startSpan(rootSpan, SPAN_NAME, startSpanOptions);
+    Span childSpan =
+        SpanBuilderImpl.createBuilder(rootSpan, SPAN_NAME, spanBuilderOptions).startSpan();
     assertThat(childSpan.getContext().isValid()).isTrue();
     assertThat(childSpan.getContext().getTraceId()).isEqualTo(rootSpan.getContext().getTraceId());
     assertThat(((SpanImpl) childSpan).toSpanData().getParentSpanId())
@@ -127,12 +112,17 @@ public class SpanFactoryImplTest {
         .isEqualTo(((SpanImpl) rootSpan).getTimestampConverter());
   }
 
+  @Test(expected = NullPointerException.class)
+  public void startRemoteSpan_NullParent() {
+    SpanBuilderImpl.createBuilderWithRemoteParent(null, SPAN_NAME, spanBuilderOptions);
+  }
+
   @Test
   public void startRemoteSpanInvalidParent() {
-    StartSpanOptions startSpanOptions = StartSpanOptions.DEFAULT;
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
     Span span =
-        spanFactory.startSpanWithRemoteParent(SpanContext.INVALID, SPAN_NAME, startSpanOptions);
+        SpanBuilderImpl.createBuilderWithRemoteParent(
+                SpanContext.INVALID, SPAN_NAME, spanBuilderOptions)
+            .startSpan();
     assertThat(span.getContext().isValid()).isTrue();
     assertThat(span.getOptions().contains(Options.RECORD_EVENTS)).isTrue();
     assertThat(span.getContext().getTraceOptions().isSampled()).isTrue();
@@ -149,9 +139,9 @@ public class SpanFactoryImplTest {
             TraceId.generateRandomId(randomHandler.current()),
             SpanId.generateRandomId(randomHandler.current()),
             TraceOptions.DEFAULT);
-    StartSpanOptions startSpanOptions = StartSpanOptions.DEFAULT;
-    when(traceConfig.getActiveTraceParams()).thenReturn(alwaysSampleTraceParams);
-    Span span = spanFactory.startSpanWithRemoteParent(spanContext, SPAN_NAME, startSpanOptions);
+    Span span =
+        SpanBuilderImpl.createBuilderWithRemoteParent(spanContext, SPAN_NAME, spanBuilderOptions)
+            .startSpan();
     assertThat(span.getContext().isValid()).isTrue();
     assertThat(span.getContext().getTraceId()).isEqualTo(spanContext.getTraceId());
     assertThat(span.getContext().getTraceOptions().isSampled()).isTrue();
diff --git a/impl_core/src/test/java/io/opencensus/trace/TracerImplTest.java b/impl_core/src/test/java/io/opencensus/trace/TracerImplTest.java
new file mode 100644
index 00000000..9ee70c98
--- /dev/null
+++ b/impl_core/src/test/java/io/opencensus/trace/TracerImplTest.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2017, Google Inc.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.trace;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import io.opencensus.testing.common.TestClock;
+import io.opencensus.trace.SpanImpl.StartEndHandler;
+import io.opencensus.trace.config.TraceConfig;
+import io.opencensus.trace.internal.RandomHandler.SecureRandomHandler;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+/** Unit tests for {@link TracerImpl}. */
+@RunWith(JUnit4.class)
+public class TracerImplTest {
+  private static final String SPAN_NAME = "MySpanName";
+  @Mock private StartEndHandler startEndHandler;
+  @Mock private TraceConfig traceConfig;
+  private TracerImpl tracer;
+
+  @Before
+  public void setUp() {
+    MockitoAnnotations.initMocks(this);
+    tracer =
+        new TracerImpl(new SecureRandomHandler(), startEndHandler, TestClock.create(), traceConfig);
+  }
+
+  @Test
+  public void createSpanBuilder() {
+    SpanBuilder spanBuilder = tracer.spanBuilder(BlankSpan.INSTANCE, SPAN_NAME);
+    assertThat(spanBuilder).isInstanceOf(SpanBuilderImpl.class);
+  }
+
+  @Test
+  public void createSpanBuilderWithRemoteParet() {
+    SpanBuilder spanBuilder = tracer.spanBuilderWithRemoteParent(SpanContext.INVALID, SPAN_NAME);
+    assertThat(spanBuilder).isInstanceOf(SpanBuilderImpl.class);
+  }
+}