Mockito Answers: Capture any exceptions

Author: garyrussell

.gitignore

@@ -19,3 +19,4 @@ erl_crash.dump
 nohup.out
 src/ant/.ant-targets-upload-dist.xml
 target
+.sts4-cache

spring-rabbit-test/src/main/java/org/springframework/amqp/rabbit/test/mockito/LambdaAnswer.java

@@ -16,12 +16,17 @@
 
 package org.springframework.amqp.rabbit.test.mockito;
 
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 
 /**
- * An Answer to optionally call the real method and allow returning a
- * custom result.
+ * An {@link Answer} to optionally call the real method and allow returning a
+ * custom result. Captures any exceptions thrown.
  *
  * @author Gary Russell
  * @since 1.6
@@ -33,6 +38,8 @@ public class LambdaAnswer<T> implements Answer<T> {
 
 	private final ValueToReturn<T> callback;
 
+	private final Set<Exception> exceptions = Collections.synchronizedSet(new LinkedHashSet<>());
+
 	public LambdaAnswer(boolean callRealMethod, ValueToReturn<T> callback) {
 		this.callRealMethod = callRealMethod;
 		this.callback = callback;
@@ -42,12 +49,28 @@ public LambdaAnswer(boolean callRealMethod, ValueToReturn<T> callback) {
 	@Override
 	public T answer(InvocationOnMock invocation) throws Throwable {
 		T result = null;
-		if (this.callRealMethod) {
-			result = (T) invocation.callRealMethod();
+		try {
+			if (this.callRealMethod) {
+				result = (T) invocation.callRealMethod();
+			}
+			return this.callback.apply(invocation, result);
+		}
+		catch (Exception e) {
+			this.exceptions.add(e);
+			throw e;
 		}
-		return this.callback.apply(invocation, result);
 	}
 
+	/**
+	 * Return the exceptions thrown, if any.
+	 * @return the exceptions.
+	 * @since 2.2.3
+	 */
+	public Collection<Exception> getExceptions() {
+		return Collections.unmodifiableCollection(this.exceptions);
+	}
+
+	@FunctionalInterface
 	public interface ValueToReturn<T> {
 
 		T apply(InvocationOnMock invocation, T result);

spring-rabbit-test/src/main/java/org/springframework/amqp/rabbit/test/mockito/LatchCountDownAndCallRealMethodAnswer.java

@@ -16,14 +16,20 @@
 
 package org.springframework.amqp.rabbit.test.mockito;
 
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 
+import org.springframework.lang.Nullable;
+
 /**
- * An Answer for void returning methods that calls the real method and
- * counts down a latch.
+ * An {@link Answer} for void returning methods that calls the real method and counts down
+ * a latch. Captures any exceptions thrown.
  *
  * @author Gary Russell
  * @since 1.6
@@ -33,6 +39,8 @@ public class LatchCountDownAndCallRealMethodAnswer implements Answer<Void> {
 
 	private final CountDownLatch latch;
 
+	private final Set<Exception> exceptions = Collections.synchronizedSet(new LinkedHashSet<>());
+
 	/**
 	 * @param count to set in a {@link CountDownLatch}.
 	 */
@@ -42,8 +50,16 @@ public LatchCountDownAndCallRealMethodAnswer(int count) {
 
 	@Override
 	public Void answer(InvocationOnMock invocation) throws Throwable {
-		invocation.callRealMethod();
-		this.latch.countDown();
+		try {
+			invocation.callRealMethod();
+		}
+		catch (Exception e) {
+			this.exceptions.add(e);
+			throw e;
+		}
+		finally {
+			this.latch.countDown();
+		}
 		return null;
 	}
 
@@ -52,4 +68,14 @@ public CountDownLatch getLatch() {
 		return latch;
 	}
 
+	/**
+	 * Return the exceptions thrown.
+	 * @return the exceptions.
+	 * @since 2.2.3
+	 */
+	@Nullable
+	public Collection<Exception> getExceptions() {
+		return Collections.unmodifiableCollection(this.exceptions);
+	}
+
 }

spring-rabbit-test/src/test/java/org/springframework/amqp/rabbit/test/ExampleRabbitListenerSpyAndCaptureTest.java

@@ -21,6 +21,7 @@
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.verify;
 
+import java.util.Collection;
 import java.util.concurrent.TimeUnit;
 
 import org.junit.jupiter.api.Test;
@@ -122,6 +123,10 @@ public void testOneWay() throws Exception {
 		assertThat((String) args[0]).isEqualTo("ex");
 		assertThat((String) args[1]).isEqualTo(queue2.getName());
 		assertThat(invocationData.getThrowable()).isNull();
+
+		Collection<Exception> exceptions = answer.getExceptions();
+		assertThat(exceptions).hasSize(1);
+		assertThat(exceptions.iterator().next()).isInstanceOf(IllegalArgumentException.class);
 	}
 
 	@Configuration
@@ -177,10 +182,10 @@ public String foo(String foo) {
 		}
 
 		@RabbitListener(id = "bar", queues = "#{queue2.name}")
-		public void foo(@Payload String foo, @Header("amqp_receivedRoutingKey") String rk) {
+		public void foo(@Payload String foo, @SuppressWarnings("unused") @Header("amqp_receivedRoutingKey") String rk) {
 			if (!failed && foo.equals("ex")) {
 				failed = true;
-				throw new RuntimeException(foo);
+				throw new IllegalArgumentException(foo);
 			}
 			failed = false;
 		}

spring-rabbit-test/src/test/java/org/springframework/amqp/rabbit/test/mockito/AnswerTests.java

@@ -17,10 +17,13 @@
 package org.springframework.amqp.rabbit.test.mockito;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.BDDMockito.willAnswer;
 import static org.mockito.Mockito.spy;
 
+import java.util.Collection;
+
 import org.junit.jupiter.api.Test;
 
 /**
@@ -40,6 +43,12 @@ public void testLambda() {
 		willAnswer(new LambdaAnswer<String>(false, (i, r) ->
 			"" + i.getArguments()[0] + i.getArguments()[0])).given(foo).foo(anyString());
 		assertThat(foo.foo("foo")).isEqualTo("foofoo");
+		LambdaAnswer<String> answer = new LambdaAnswer<>(true, (inv, result) -> result);
+		willAnswer(answer).given(foo).foo("fail");
+		assertThatIllegalArgumentException().isThrownBy(() -> foo.foo("fail"));
+		Collection<Exception> exceptions = answer.getExceptions();
+		assertThat(exceptions).hasSize(1);
+		assertThat(exceptions.iterator().next()).isInstanceOf(IllegalArgumentException.class);
 	}
 
 	private static class Foo {
@@ -49,6 +58,9 @@ private static class Foo {
 		}
 
 		public String foo(String foo) {
+			if (foo.equals("fail")) {
+				throw new IllegalArgumentException("fail");
+			}
 			return foo.toUpperCase();
 		}
 

src/reference/asciidoc/testing.adoc

@@ -73,19 +73,9 @@ assertEquals("thingthing", thing.thing("thing"));
 ----
 ====
 
-The following example shows how to test the `Thing` POJO with Java 7 or earlier:
+Starting with version 2.2.3, the answers capture any exceptions thrown by the method under test.
+Use `answer.getExceptions()` to get a reference to them.
 
-====
-[source, java]
-----
-doAnswer(new LambdaAnswer<String>(true, new ValueToReturn<String>() {
-    @Override
-    public String apply(InvocationOnMock i, String r) {
-        return r + r;
-    }
-})).when(thing).thing(anyString());
-----
-====
 
 [[test-harness]]
 ==== `@RabbitListenerTest` and `RabbitListenerTestHarness`