Add test

src/objective-c/tests/InteropTests.m

@@ -457,4 +457,99 @@
   [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
 }
 
+- (void)testAlternateDispatchQueue {
+  XCTAssertNotNil(self.class.host);
+  __weak XCTestExpectation *expectation1 = [self expectationWithDescription:@"AlternateDispatchQueue1"];
+
+  NSArray *requests = @[@27182, @8, @1828, @45904];
+  NSArray *responses = @[@31415, @9, @2653, @58979];
+
+  // Set the default dispatch queue
+  NSString *queue1_label = @"test.queue1";
+  NSString *queue2_label = @"test.queue2";
+  dispatch_queue_t queue1 = dispatch_queue_create([queue1_label UTF8String], DISPATCH_QUEUE_SERIAL);
+  dispatch_queue_t queue2 = dispatch_queue_create([queue2_label UTF8String], DISPATCH_QUEUE_SERIAL);
+  [_service setDefaultResponseDispatchQueue:queue1];
+  GRXBufferedPipe *requestsBuffer1 = [[GRXBufferedPipe alloc] init];
+
+  __block int index = 0;
+
+  id request = [RMTStreamingOutputCallRequest messageWithPayloadSize:requests[index]
+                                               requestedResponseSize:responses[index]];
+  [requestsBuffer1 writeValue:request];
+
+  [_service fullDuplexCallWithRequestsWriter:requestsBuffer1
+                                eventHandler:^(BOOL done,
+                                               RMTStreamingOutputCallResponse *response,
+                                               NSError *error) {
+    XCTAssertNil(error, @"Finished with unexpected error: %@", error);
+    XCTAssertTrue(done || response, @"Event handler called without an event.");
+    NSString *label = [NSString stringWithUTF8String:dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL)];
+    XCTAssert([label isEqualToString:queue1_label]);
+
+    if (response) {
+      XCTAssertLessThan(index, 4, @"More than 4 responses received.");
+      id expected = [RMTStreamingOutputCallResponse messageWithPayloadSize:responses[index]];
+      XCTAssertEqualObjects(response, expected);
+      index += 1;
+      if (index < 4) {
+        id request = [RMTStreamingOutputCallRequest messageWithPayloadSize:requests[index]
+                                                     requestedResponseSize:responses[index]];
+        [requestsBuffer1 writeValue:request];
+      } else {
+        [requestsBuffer1 writesFinishedWithError:nil];
+      }
+    }
+
+    if (done) {
+      XCTAssertEqual(index, 4, @"Received %i responses instead of 4.", index);
+      [expectation1 fulfill];
+    }
+  }];
+
+  [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
+
+  // Test overriding default queue with another queue
+  __weak XCTestExpectation *expectation2 = [self expectationWithDescription:@"AlternateDispatchQueue2"];
+  GRXBufferedPipe *requestsBuffer2 = [[GRXBufferedPipe alloc] init];
+
+  index = 0;
+
+  [requestsBuffer2 writeValue:request];
+
+  GRPCProtoCall *rpc = [_service RPCToFullDuplexCallWithRequestsWriter:requestsBuffer2
+                                eventHandler:^(BOOL done,
+                                               RMTStreamingOutputCallResponse *response,
+                                               NSError *error) {
+    XCTAssertNil(error, @"Finished with unexpected error: %@", error);
+    XCTAssertTrue(done || response, @"Event handler called without an event.");
+    NSString *label = [NSString stringWithUTF8String:dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL)];
+    XCTAssert([label isEqualToString:queue2_label]);
+
+    if (response) {
+      XCTAssertLessThan(index, 4, @"More than 4 responses received.");
+      id expected = [RMTStreamingOutputCallResponse messageWithPayloadSize:responses[index]];
+      XCTAssertEqualObjects(response, expected);
+      index += 1;
+      if (index < 4) {
+        id request = [RMTStreamingOutputCallRequest messageWithPayloadSize:requests[index]
+                                                     requestedResponseSize:responses[index]];
+        [requestsBuffer2 writeValue:request];
+      } else {
+        [requestsBuffer2 writesFinishedWithError:nil];
+      }
+    }
+
+    if (done) {
+      XCTAssertEqual(index, 4, @"Received %i responses instead of 4.", index);
+      [expectation2 fulfill];
+    }
+  }];
+  [rpc setResponseDispatchQueue:queue2];
+  [rpc start];
+
+  [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
+  [_service setDefaultResponseDispatchQueue:dispatch_get_main_queue()];
+}
+
 @end