SystemClock: add test

Bug: 28357356

Change-Id: Idf66c048bda09cd8cb08adf89ed0edd3770c4e39
Signed-off-by: Greg Hackmann <ghackmann@google.com>

2 files changed, 75 insertions, 0 deletions

diff --git a/libutils/tests/Android.mk b/libutils/tests/Android.mk
index 8f07f1ad1..21fe19c96 100644
--- a/libutils/tests/Android.mk
+++ b/libutils/tests/Android.mk
@@ -28,6 +28,7 @@ LOCAL_SRC_FILES := \
     LruCache_test.cpp \
     String8_test.cpp \
     StrongPointer_test.cpp \
+    SystemClock_test.cpp \
     Unicode_test.cpp \
     Vector_test.cpp \
 
diff --git a/libutils/tests/SystemClock_test.cpp b/libutils/tests/SystemClock_test.cpp
new file mode 100644
index 000000000..5ad060b04
--- /dev/null
+++ b/libutils/tests/SystemClock_test.cpp
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include <unistd.h>
+#include <utils/SystemClock.h>
+
+#include <gtest/gtest.h>
+
+static const auto MS_IN_NS = 1000000;
+
+static const int64_t SLEEP_MS = 500;
+static const int64_t SLEEP_NS = SLEEP_MS * MS_IN_NS;
+// Conservatively assume that we might be descheduled for up to 50 ms
+static const int64_t SLACK_MS = 50;
+static const int64_t SLACK_NS = SLACK_MS * MS_IN_NS;
+
+TEST(SystemClock, SystemClock) {
+    auto startUptimeMs = android::uptimeMillis();
+    auto startRealtimeMs = android::elapsedRealtime();
+    auto startRealtimeNs = android::elapsedRealtimeNano();
+
+    ASSERT_GT(startUptimeMs, 0)
+            << "uptimeMillis() reported an impossible uptime";
+    ASSERT_GE(startRealtimeMs, startUptimeMs)
+            << "elapsedRealtime() thinks we've suspended for negative time";
+    ASSERT_GE(startRealtimeNs, startUptimeMs * MS_IN_NS)
+            << "elapsedRealtimeNano() thinks we've suspended for negative time";
+
+    ASSERT_GE(startRealtimeNs, startRealtimeMs * MS_IN_NS)
+            << "elapsedRealtime() and elapsedRealtimeNano() are inconsistent";
+    ASSERT_LT(startRealtimeNs, (startRealtimeMs + SLACK_MS) * MS_IN_NS)
+            << "elapsedRealtime() and elapsedRealtimeNano() are inconsistent";
+
+    timespec ts;
+    ts.tv_sec = 0;
+    ts.tv_nsec = SLEEP_MS * MS_IN_NS;
+    auto nanosleepErr = TEMP_FAILURE_RETRY(nanosleep(&ts, nullptr));
+    ASSERT_EQ(nanosleepErr, 0) << "nanosleep() failed: " << strerror(errno);
+
+    auto endUptimeMs = android::uptimeMillis();
+    auto endRealtimeMs = android::elapsedRealtime();
+    auto endRealtimeNs = android::elapsedRealtimeNano();
+
+    EXPECT_GE(endUptimeMs - startUptimeMs, SLEEP_MS)
+            << "uptimeMillis() advanced too little after nanosleep()";
+    EXPECT_LT(endUptimeMs - startUptimeMs, SLEEP_MS + SLACK_MS)
+            << "uptimeMillis() advanced too much after nanosleep()";
+    EXPECT_GE(endRealtimeMs - startRealtimeMs, SLEEP_MS)
+            << "elapsedRealtime() advanced too little after nanosleep()";
+    EXPECT_LT(endRealtimeMs - startRealtimeMs, SLEEP_MS + SLACK_MS)
+            << "elapsedRealtime() advanced too much after nanosleep()";
+    EXPECT_GE(endRealtimeNs - startRealtimeNs, SLEEP_NS)
+            << "elapsedRealtimeNano() advanced too little after nanosleep()";
+    EXPECT_LT(endRealtimeNs - startRealtimeNs, SLEEP_NS + SLACK_NS)
+            << "elapsedRealtimeNano() advanced too much after nanosleep()";
+
+    EXPECT_GE(endRealtimeNs, endRealtimeMs * MS_IN_NS)
+            << "elapsedRealtime() and elapsedRealtimeNano() are inconsistent after nanosleep()";
+    EXPECT_LT(endRealtimeNs, (endRealtimeMs + SLACK_MS) * MS_IN_NS)
+            << "elapsedRealtime() and elapsedRealtimeNano() are inconsistent after nanosleep()";
+}