Improve support of async request in MockMvcTester

This commit improves the handling of asynchronous requests by offering
a way to opt-in for the raw async result. This provides first class
support for asserting a request that might still be in process as well
as the asyncResult, if necessary.

See gh-33040

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/MockMvcTester.java

@@ -448,6 +448,8 @@ public final class MockMvcTester {
 		 * assertThat(mvc.get().uri("/greet")).hasStatusOk();
 		 * assertThat(mvc.get().uri("/greet").exchange()).hasStatusOk();
 		 * </code></pre>
+		 * <p>For assertions on the original asynchronous request that might
+		 * still be in progress, use {@link #asyncExchange()}.
 		 * @see #exchange(Duration) to customize the timeout for async requests
 		 */
 		public MvcTestResult exchange() {
@@ -458,12 +460,23 @@ public final class MockMvcTester {
 		 * Execute the request and wait at most the given {@code timeToWait}
 		 * duration for the asynchronous request to complete. If the request
 		 * is not asynchronous, the {@code timeToWait} is ignored.
+		 * <p>For assertions on the original asynchronous request that might
+		 * still be in progress, use {@link #asyncExchange()}.
 		 * @see #exchange()
 		 */
 		public MvcTestResult exchange(Duration timeToWait) {
 			return MockMvcTester.this.exchange(this, timeToWait);
 		}
 
+		/**
+		 * Execute the request and do not attempt to wait for the completion of
+		 * an asynchronous request. Contrary to {@link #exchange()}, this returns
+		 * the original result that might still be in progress.
+		 */
+		public MvcTestResult asyncExchange() {
+			return MockMvcTester.this.perform(this);
+		}
+
 		@Override
 		public MvcTestResultAssert assertThat() {
 			return new MvcTestResultAssert(exchange(), MockMvcTester.this.jsonMessageConverter);
@@ -493,6 +506,8 @@ public final class MockMvcTester {
 		 * assertThat(mvc.get().uri("/greet")).hasStatusOk();
 		 * assertThat(mvc.get().uri("/greet").exchange()).hasStatusOk();
 		 * </code></pre>
+		 * <p>For assertions on the original asynchronous request that might
+		 * still be in progress, use {@link #asyncExchange()}.
 		 * @see #exchange(Duration) to customize the timeout for async requests
 		 */
 		public MvcTestResult exchange() {
@@ -503,12 +518,23 @@ public final class MockMvcTester {
 		 * Execute the request and wait at most the given {@code timeToWait}
 		 * duration for the asynchronous request to complete. If the request
 		 * is not asynchronous, the {@code timeToWait} is ignored.
+		 * <p>For assertions on the original asynchronous request that might
+		 * still be in progress, use {@link #asyncExchange()}.
 		 * @see #exchange()
 		 */
 		public MvcTestResult exchange(Duration timeToWait) {
 			return MockMvcTester.this.exchange(this, timeToWait);
 		}
 
+		/**
+		 * Execute the request and do not attempt to wait for the completion of
+		 * an asynchronous request. Contrary to {@link #exchange()}, this returns
+		 * the original result that might still be in progress.
+		 */
+		public MvcTestResult asyncExchange() {
+			return MockMvcTester.this.perform(this);
+		}
+
 		@Override
 		public MvcTestResultAssert assertThat() {
 			return new MvcTestResultAssert(exchange(), MockMvcTester.this.jsonMessageConverter);

spring-test/src/test/java/org/springframework/test/web/servlet/assertj/MockMvcTesterIntegrationTests.java

@@ -55,6 +55,7 @@ import org.springframework.stereotype.Controller;
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
 import org.springframework.test.web.Person;
 import org.springframework.test.web.servlet.ResultMatcher;
+import org.springframework.test.web.servlet.assertj.MockMvcTester.MockMultipartMvcRequestBuilder;
 import org.springframework.test.web.servlet.assertj.MockMvcTester.MockMvcRequestBuilder;
 import org.springframework.ui.Model;
 import org.springframework.validation.Errors;
@@ -105,6 +106,9 @@ public class MockMvcTesterIntegrationTests {
 	@Nested
 	class PerformTests {
 
+		private final MockMultipartFile file = new MockMultipartFile("file", "content.txt", null,
+				"value".getBytes(StandardCharsets.UTF_8));
+
 		@Test
 		void syncRequestWithDefaultExchange() {
 			assertThat(mvc.get().uri("/greet")).hasStatusOk();
@@ -116,6 +120,13 @@ public class MockMvcTesterIntegrationTests {
 					.hasBodyTextEqualTo("name=Joe&someBoolean=true");
 		}
 
+		@Test
+		void asyncMultipartRequestWithDefaultExchange() {
+			assertThat(mvc.post().uri("/multipart-streaming").multipart()
+					.file(this.file).param("timeToWait", "100"))
+					.hasStatusOk().hasBodyTextEqualTo("name=Joe&file=content.txt");
+		}
+
 		@Test
 		void syncRequestWithExplicitExchange() {
 			assertThat(mvc.get().uri("/greet").exchange()).hasStatusOk();
@@ -127,6 +138,13 @@ public class MockMvcTesterIntegrationTests {
 					.hasStatusOk().hasBodyTextEqualTo("name=Joe&someBoolean=true");
 		}
 
+		@Test
+		void asyncMultipartRequestWitExplicitExchange() {
+			assertThat(mvc.post().uri("/multipart-streaming").multipart()
+					.file(this.file).param("timeToWait", "100").exchange())
+					.hasStatusOk().hasBodyTextEqualTo("name=Joe&file=content.txt");
+		}
+
 		@Test
 		void syncRequestWithExplicitExchangeIgnoresDuration() {
 			Duration timeToWait = mock(Duration.class);
@@ -140,6 +158,13 @@ public class MockMvcTesterIntegrationTests {
 					.hasStatusOk().hasBodyTextEqualTo("name=Joe&someBoolean=true");
 		}
 
+		@Test
+		void asyncMultipartRequestWithExplicitExchangeAndEnoughTimeToWait() {
+			assertThat(mvc.post().uri("/multipart-streaming").multipart()
+					.file(this.file).param("timeToWait", "100").exchange(Duration.ofMillis(200)))
+					.hasStatusOk().hasBodyTextEqualTo("name=Joe&file=content.txt");
+		}
+
 		@Test
 		void asyncRequestWithExplicitExchangeAndNotEnoughTimeToWait() {
 			MockMvcRequestBuilder builder = mvc.get().uri("/streaming").param("timeToWait", "500");
@@ -147,6 +172,15 @@ public class MockMvcTesterIntegrationTests {
 					.isThrownBy(() -> builder.exchange(Duration.ofMillis(100)))
 					.withMessageContaining("was not set during the specified timeToWait=100");
 		}
+
+		@Test
+		void asyncMultipartRequestWithExplicitExchangeAndNotEnoughTimeToWait() {
+			MockMultipartMvcRequestBuilder builder = mvc.post().uri("/multipart-streaming").multipart()
+					.file(this.file).param("timeToWait", "500");
+			assertThatIllegalStateException()
+					.isThrownBy(() -> builder.exchange(Duration.ofMillis(100)))
+					.withMessageContaining("was not set during the specified timeToWait=100");
+		}
 	}
 
 	@Nested
@@ -154,14 +188,13 @@ public class MockMvcTesterIntegrationTests {
 
 		@Test
 		void hasAsyncStartedTrue() {
-			// Need #perform as the regular exchange waits for async completion automatically
-			assertThat(mvc.perform(mvc.get().uri("/callable").accept(MediaType.APPLICATION_JSON)))
+			assertThat(mvc.get().uri("/callable").accept(MediaType.APPLICATION_JSON).asyncExchange())
 					.request().hasAsyncStarted(true);
 		}
 
 		@Test
 		void hasAsyncStartedFalse() {
-			assertThat(mvc.get().uri("/greet")).request().hasAsyncStarted(false);
+			assertThat(mvc.get().uri("/greet").asyncExchange()).request().hasAsyncStarted(false);
 		}
 
 		@Test
@@ -325,8 +358,7 @@ public class MockMvcTesterIntegrationTests {
 
 		@Test
 		void asyncResult() {
-			// Need #perform as the regular exchange waits for async completion automatically
-			MvcTestResult result = mvc.perform(mvc.get().uri("/callable").accept(MediaType.APPLICATION_JSON));
+			MvcTestResult result = mvc.get().uri("/callable").accept(MediaType.APPLICATION_JSON).asyncExchange();
 			assertThat(result.getMvcResult().getAsyncResult())
 					.asInstanceOf(InstanceOfAssertFactories.map(String.class, Object.class))
 					.containsOnly(entry("key", "value"));
@@ -694,9 +726,24 @@ public class MockMvcTesterIntegrationTests {
 		}
 
 		@PutMapping("/multipart-put")
-		public ModelAndView multiPartViaHttpPut(@RequestParam MultipartFile file) {
+		ModelAndView multiPartViaHttpPut(@RequestParam MultipartFile file) {
 			return new ModelAndView("index", Map.of("name", file.getName()));
 		}
+
+		@PostMapping("/multipart-streaming")
+		StreamingResponseBody streaming(@RequestParam MultipartFile file, @RequestParam long timeToWait) {
+			return out -> {
+				PrintStream stream = new PrintStream(out, true, StandardCharsets.UTF_8);
+				stream.print("name=Joe");
+				try {
+					Thread.sleep(timeToWait);
+					stream.print("&file=" + file.getOriginalFilename());
+				}
+				catch (InterruptedException e) {
+					/* no-op */
+				}
+			};
+		}
 	}
 
 	@Controller

spring-test/src/test/java/org/springframework/test/web/servlet/samples/standalone/AsyncTests.java

@@ -32,7 +32,6 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.test.web.Person;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MvcResult;
-import org.springframework.test.web.servlet.RequestBuilder;
 import org.springframework.test.web.servlet.assertj.MockMvcTester;
 import org.springframework.test.web.servlet.assertj.MvcTestResult;
 import org.springframework.web.bind.annotation.ExceptionHandler;
@@ -265,9 +264,7 @@ class AsyncTests {
 		void printAsyncResult() {
 			StringWriter asyncWriter = new StringWriter();
 
-			// Use #perform to not complete asynchronous request automatically
-			RequestBuilder requestBuilder = this.mockMvc.get().uri("/1").param("deferredResult", "true");
-			MvcTestResult result = this.mockMvc.perform(requestBuilder);
+			MvcTestResult result = this.mockMvc.get().uri("/1").param("deferredResult", "true").asyncExchange();
 			assertThat(result).debug(asyncWriter).request().hasAsyncStarted(true);
 			assertThat(asyncWriter.toString()).contains("Async started = true");
 			asyncWriter = new StringWriter(); // Reset