Removed bogus Looper.prepare() from onStart(). (DO NOT MERGE)

The instrumentation thread for JUnit tests is not a Looper. It calculates all tests that need to be executed, executes them, and exits, ending the instrumentation.

Bug: 17418699

Change-Id: Idcfdd3369472e01996bfae5564b6cb70c3eb7724

2 files changed, 52 insertions, 15 deletions

diff --git a/support/src/android/support/test/runner/AndroidJUnitRunner.java b/support/src/android/support/test/runner/AndroidJUnitRunner.java
index f07bf0c..07b9ea0 100644
--- a/support/src/android/support/test/runner/AndroidJUnitRunner.java
+++ b/support/src/android/support/test/runner/AndroidJUnitRunner.java
@@ -223,21 +223,10 @@ public class AndroidJUnitRunner extends MonitoringInstrumentation {
         return tagString != null && Boolean.parseBoolean(tagString);
     }
 
-    /**
-     * Initialize the current thread as a looper.
-     * <p/>
-     * Exposed for unit testing.
-     */
-    void prepareLooper() {
-        Looper.prepare();
-    }
-
     @Override
     public void onStart() {
         super.onStart();
 
-        prepareLooper();
-
         if (getBooleanArgument(ARGUMENT_DEBUG)) {
             Debug.waitForDebugger();
         }
diff --git a/support/tests/src/android/support/test/runner/AndroidJUnitRunnerTest.java b/support/tests/src/android/support/test/runner/AndroidJUnitRunnerTest.java
index 245612a..2fcdca4 100644
--- a/support/tests/src/android/support/test/runner/AndroidJUnitRunnerTest.java
+++ b/support/tests/src/android/support/test/runner/AndroidJUnitRunnerTest.java
@@ -17,8 +17,13 @@ package android.support.test.runner;
 
 import android.content.Context;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
 import android.support.test.internal.runner.TestRequestBuilder;
 
+import junit.framework.Assert;
+
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -28,20 +33,20 @@ import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
 
-import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.PrintStream;
-import java.io.Reader;
-import java.io.StringReader;
 
 /**
  * Unit tests for {@link AndroidJUnitRunner}.
  */
 public class AndroidJUnitRunnerTest {
+    public static final int SLEEP_TIME = 300;
+
+    private final Thread mInstantiationThread = Thread.currentThread();
 
     private AndroidJUnitRunner mAndroidJUnitRunner;
     private PrintStream mStubStream;
@@ -54,7 +59,6 @@ public class AndroidJUnitRunnerTest {
     public void setUp() throws Exception {
         mAndroidJUnitRunner = new AndroidJUnitRunner() {
 
-
             @Override
             TestRequestBuilder createTestRequestBuilder(PrintStream writer,
                     String... packageCodePaths) {
@@ -148,4 +152,48 @@ public class AndroidJUnitRunnerTest {
         Mockito.verify(mMockBuilder).addTestClass("ClassName3");
         Mockito.verify(mMockBuilder).addTestMethod("ClassName4", "method2");
     }
+
+    /**
+     * Ensures that the main looper is not blocked and can process
+     * messages during test execution.
+     */
+    @Test
+    public void testMainLooperIsAlive() throws InterruptedException {
+        final boolean[] called = new boolean[1];
+        Handler handler = new Handler(Looper.getMainLooper()) {
+            @Override
+            public void handleMessage(Message msg) {
+                called[0] = true;
+            }
+        };
+        handler.sendEmptyMessage(0);
+        Thread.sleep(SLEEP_TIME);
+        Assert.assertTrue(called[0]);
+    }
+
+    /**
+     * Ensures that the thread the test runs on has not been
+     * prepared as a looper.  It doesn't make sense for it
+     * to be a looper because it will be blocked for the entire
+     * duration of test execution.  Tests should instead post
+     * messages to the main looper or a new handler thread
+     * of their own as appropriate while running.
+     */
+    @Test
+    public void testTestThreadIsNotALooper() {
+        Assert.assertNull(Looper.myLooper());
+    }
+
+    /**
+     * Ensures that tests run on the same thread they were
+     * instantiated on.  This is needed to ensure that
+     * objects created by the test don't accidentally bind
+     * to thread-local state belonging to other threads.
+     * In particular, this ensures that the test cannot
+     * create Handlers that are bound to the wrong thread.
+     */
+    @Test
+    public void testTestRunsOnSameThreadAsInstantiation() {
+        Assert.assertEquals(Thread.currentThread(), mInstantiationThread);
+    }
 }