Serialize threading for download manager testing.

The download manager uses threading in a simple way -- it launches two
threads, UpdateThread and DownloadThread, and both are "fire and
forget".  This is fortunate for testing, since it means we can
eliminate multithreading and simply run each thread in order, and
everything still works.

This change does just that, abstracting Thread.start() behind
SystemFacade and making FakeSystemFacade put new threads into a queue
and then run through them serially.  This simplifies much of the test
code and makes it all much more predictable.

I've simplified the test code as much as possible here and moved a few
more tests over to PublicApiFunctionalTest, leaving only a minimum in
DownloadManagerFunctionalTest, which will eventually be deleted
altogether.  I've also improved testing in some areas -- for example,
we can now test that running notifications get cancelled after the
download completes in a robust way.

There is one test case that checks for race conditions and requires
multithreading.  I've moved this into a new ThreadingTest class, which
uses a custom FakeSystemFacade that allows multithreading.  I've
extracted AbstractPublicApiTest for the newly shared code.

Change-Id: Ic1d5c76bfa9913fe053174c3d8b516790ca8b25f

4 files changed, 12 insertions, 2 deletions

diff --git a/src/com/android/providers/downloads/DownloadInfo.java b/src/com/android/providers/downloads/DownloadInfo.java
index 29c2d490..ee3ca544 100644
--- a/src/com/android/providers/downloads/DownloadInfo.java
+++ b/src/com/android/providers/downloads/DownloadInfo.java
@@ -369,6 +369,6 @@ public class DownloadInfo {
         }
         DownloadThread downloader = new DownloadThread(mContext, mSystemFacade, this);
         mHasActiveThread = true;
-        downloader.start();
+        mSystemFacade.startThread(downloader);
     }
 }
diff --git a/src/com/android/providers/downloads/DownloadService.java b/src/com/android/providers/downloads/DownloadService.java
index a6175953..c9443fd5 100644
--- a/src/com/android/providers/downloads/DownloadService.java
+++ b/src/com/android/providers/downloads/DownloadService.java
@@ -258,7 +258,7 @@ public class DownloadService extends Service {
             mPendingUpdate = true;
             if (mUpdateThread == null) {
                 mUpdateThread = new UpdateThread();
-                mUpdateThread.start();
+                mSystemFacade.startThread(mUpdateThread);
             }
         }
     }
diff --git a/src/com/android/providers/downloads/RealSystemFacade.java b/src/com/android/providers/downloads/RealSystemFacade.java
index 1d9e64a9..adf0107a 100644
--- a/src/com/android/providers/downloads/RealSystemFacade.java
+++ b/src/com/android/providers/downloads/RealSystemFacade.java
@@ -87,4 +87,9 @@ class RealSystemFacade implements SystemFacade {
     public void cancelAllNotifications() {
         mNotificationManager.cancelAll();
     }
+
+    @Override
+    public void startThread(Thread thread) {
+        thread.start();
+    }
 }
diff --git a/src/com/android/providers/downloads/SystemFacade.java b/src/com/android/providers/downloads/SystemFacade.java
index e41644ab..3f8ff264 100644
--- a/src/com/android/providers/downloads/SystemFacade.java
+++ b/src/com/android/providers/downloads/SystemFacade.java
@@ -53,4 +53,9 @@ interface SystemFacade {
      * Cancel all system notifications.
      */
     public void cancelAllNotifications();
+
+    /**
+     * Start a thread.
+     */
+    public void startThread(Thread thread);
 }