Don't report an error for empty test runs.

Tests are commonly run with size or other filters. It is incorrect to report
errors if a test package doesn't happen to have tests of the given size.
Plus '0 tests is not an error' is the InstrumentationTestRunner behavior.

Change-Id: Ifaa2abc6bffd57ff514277e8c7e4ddf33345023c

2 files changed, 60 insertions, 3 deletions

diff --git a/support/src/android/support/test/internal/runner/TestRequestBuilder.java b/support/src/android/support/test/internal/runner/TestRequestBuilder.java
index cf0e6c9..0d7cd8c 100644
--- a/support/src/android/support/test/internal/runner/TestRequestBuilder.java
+++ b/support/src/android/support/test/internal/runner/TestRequestBuilder.java
@@ -32,6 +32,8 @@ import org.junit.runner.Description;
 import org.junit.runner.Request;
 import org.junit.runner.Runner;
 import org.junit.runner.manipulation.Filter;
+import org.junit.runner.manipulation.NoTestsRemainException;
+import org.junit.runner.notification.RunNotifier;
 import org.junit.runners.model.InitializationError;
 
 import java.io.IOException;
@@ -228,6 +230,47 @@ public class TestRequestBuilder {
         }
     }
 
+    /**
+     * A {@link Request} that doesn't report an error if all tests are filtered out. Done for
+     * consistency with InstrumentationTestRunner.
+     */
+    private static class LenientFilterRequest extends Request {
+        private final Request mRequest;
+        private final Filter mFilter;
+
+        public LenientFilterRequest(Request classRequest, Filter filter) {
+            mRequest = classRequest;
+            mFilter = filter;
+        }
+
+        @Override
+        public Runner getRunner() {
+            try {
+                Runner runner = mRequest.getRunner();
+                mFilter.apply(runner);
+                return runner;
+            } catch (NoTestsRemainException e) {
+                // don't treat filtering out all tests as an error
+                return new BlankRunner();
+            }
+        }
+    }
+
+    /**
+     * A {@link Runner} that doesn't do anything
+     */
+    private static class BlankRunner extends Runner {
+        @Override
+        public Description getDescription() {
+            return Description.createSuiteDescription("no tests found");
+        }
+
+        @Override
+        public void run(RunNotifier notifier) {
+            // do nothing
+        }
+    }
+
     public TestRequestBuilder(PrintStream writer, String... apkPaths) {
         mApkPaths = apkPaths;
         mTestLoader = new TestLoader(writer);
@@ -364,7 +407,7 @@ public class TestRequestBuilder {
 
         Request request = classes(instr, bundle, mSkipExecution, new Computer(),
                 mTestLoader.getLoadedClasses().toArray(new Class[0]));
-        return new TestRequest(mTestLoader.getLoadFailures(), request.filterWith(mFilter));
+        return new TestRequest(mTestLoader.getLoadFailures(), new LenientFilterRequest(request, mFilter));
     }
 
     /**
diff --git a/support/tests/src/android/support/test/internal/runner/TestRequestBuilderTest.java b/support/tests/src/android/support/test/internal/runner/TestRequestBuilderTest.java
index 81cf3f7..9da0ba3 100644
--- a/support/tests/src/android/support/test/internal/runner/TestRequestBuilderTest.java
+++ b/support/tests/src/android/support/test/internal/runner/TestRequestBuilderTest.java
@@ -521,8 +521,8 @@ public class TestRequestBuilderTest {
         // The last iteration through the loop doesn't add a ShardingFilter - it runs all the
         // tests to establish a baseline for the total number that should have been run.
         for (int i = 0; i < 5; i++) {
-            TestRequestBuilder b
-                    = new TestRequestBuilder(new PrintStream(new ByteArrayOutputStream()));
+            TestRequestBuilder b = new TestRequestBuilder(new PrintStream(
+                    new ByteArrayOutputStream()));
             if (i < 4) {
                 b.addShardingFilter(4, i);
             }
@@ -549,4 +549,18 @@ public class TestRequestBuilderTest {
             Assert.assertTrue(results[i].getRunCount() < totalRun);
         }
     }
+
+    /**
+     * Verify that filtering out all tests is not treated as an error
+     */
+    @Test
+    public void testNoTests() {
+        TestRequestBuilder b = new TestRequestBuilder(new PrintStream(new ByteArrayOutputStream()));
+        b.addTestClass(SampleTest.class.getName());
+        b.addTestSizeFilter("medium");
+        TestRequest request = b.build(mInstr, mBundle);
+        JUnitCore testRunner = new JUnitCore();
+        Result result = testRunner.run(request.getRequest());
+        Assert.assertEquals(0, result.getRunCount());
+    }
 }