[mojo] Enable ServiceRegistryImpl to override remote services

third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html

Index: third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html
diff --git a/third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html b/third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html
index c16f63c0bdc2c57eb1e150b3ab628235ac195208..79cbcec02d37a55fdd74b426eb1258f945a70e06 100644
--- a/third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html
+++ b/third_party/WebKit/LayoutTests/harness-tests/mojo-helpers.html
@@ -13,4 +13,59 @@ mojo_test(mojo => {
   assert_true(mojo.router instanceof Object);
   assert_true(mojo.serviceRegistry instanceof Object);
 }, 'Mojo system APIs should be available to layout tests.');
+
+mojo_test(mojo => {
+  return new Promise(resolve => {
+    // Complete the test as soon as a request comes in for a Frobinator service.
+    mojo.serviceRegistry.addServiceOverrideForTesting('Frobinator', resolve);
+
+    // Try to connect to the browser's Frobinator service. This should be
+    // intercepted by the above override.
+    mojo.serviceRegistry.connectToService('Frobinator');
+  });
+}, 'Service registry overrides should be properly intercepted.');
+
+mojo_test(mojo => {
+  return new Promise(resolve => {
+    let TEST_REQUEST = new Uint8Array([42, 0, 2, 3, 5, 7, 11, 13, 17, 19, 23]);
+
+    mojo.serviceRegistry.addServiceOverrideForTesting('Frobinator', pipe => {
+      resolve(mojo_wait_for_incoming_message(mojo, pipe)
+        .then(message => {
+          assert_array_equals(new Uint8Array(message.buffer), TEST_REQUEST);
+          assert_array_equals(message.handles, []);
+        }));
+    });
+
+    let pipe = mojo.serviceRegistry.connectToService('Frobinator');
+    assert_equals(mojo.core.writeMessage(pipe, TEST_REQUEST, [], 0),
+        mojo.core.RESULT_OK);
+  });
+}, 'Mock services can receive messages from test code.');
+
+mojo_test(mojo => {
+  let TEST_REQUEST = new Uint8Array([1, 2, 3, 4, 5]);
+  let EXPECTED_RESPONSE = new Uint8Array([5, 4, 3, 2, 1]);
+
+  // Mock service should respond to any message with its reverse.
+  mojo.serviceRegistry.addServiceOverrideForTesting('Reversinator', pipe => {
+    mojo_wait_for_incoming_message(mojo, pipe)
+      .then(message => {
+        let response = new Uint8Array(message.buffer);
+        response.reverse();
+        assert_equals(mojo.core.writeMessage(pipe, response, [], 0),
+            mojo.core.RESULT_OK);
+      });
+  });
+
+  let pipe = mojo.serviceRegistry.connectToService('Reversinator');
+  assert_equals(mojo.core.writeMessage(pipe, TEST_REQUEST, [], 0),
+      mojo.core.RESULT_OK);
+
+  return mojo_wait_for_incoming_message(mojo, pipe)
+    .then(response => {
+      assert_array_equals(new Uint8Array(response.buffer), EXPECTED_RESPONSE);
+      assert_array_equals(response.handles, []);
+    });
+}, 'Test code can receive response messages from mock services.');
 </script>