Allow to chain ContextConsumer implementations

Closes gh-26723

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/runner/ContextConsumer.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.boot.test.context.runner;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.util.Assert;
 
 /**
  * Callback interface used to process an {@link ApplicationContext} with the ability to
@@ -38,4 +39,20 @@ public interface ContextConsumer<C extends ApplicationContext> {
 	 */
 	void accept(C context) throws Throwable;
 
+	/**
+	 * Returns a composed {@code ContextConsumer} that performs, in sequence, this
+	 * operation followed by the {@code after} operation.
+	 * @param after the operation to perform after this operation
+	 * @return a composed {@code ContextConsumer} that performs in sequence this operation
+	 * followed by the {@code after} operation
+	 * @since 2.6.0
+	 */
+	default ContextConsumer<C> andThen(ContextConsumer<? super C> after) {
+		Assert.notNull(after, "After must not be null");
+		return (context) -> {
+			accept(context);
+			after.accept(context);
+		};
+	}
+
 }

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/ContextConsumerTests.java

+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.test.context.runner;
+
+import java.util.function.IntPredicate;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.InOrder;
+
+import org.springframework.context.ApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+/**
+ * Tests for {@link ContextConsumer}.
+ *
+ * @author Stephane Nicoll
+ */
+class ContextConsumerTests {
+
+	@Test
+	void andThenInvokeInOrder() throws Throwable {
+		IntPredicate predicate = mock(IntPredicate.class);
+		given(predicate.test(42)).willReturn(true);
+		given(predicate.test(24)).willReturn(false);
+		ContextConsumer<ApplicationContext> firstConsumer = (context) -> assertThat(predicate.test(42)).isTrue();
+		ContextConsumer<ApplicationContext> secondConsumer = (context) -> assertThat(predicate.test(24)).isFalse();
+		firstConsumer.andThen(secondConsumer).accept(mock(ApplicationContext.class));
+		InOrder ordered = inOrder(predicate);
+		ordered.verify(predicate).test(42);
+		ordered.verify(predicate).test(24);
+		ordered.verifyNoMoreInteractions();
+	}
+
+	@Test
+	void andThenNoInvokedIfThisFails() {
+		IntPredicate predicate = mock(IntPredicate.class);
+		given(predicate.test(42)).willReturn(true);
+		given(predicate.test(24)).willReturn(false);
+		ContextConsumer<ApplicationContext> firstConsumer = (context) -> assertThat(predicate.test(42)).isFalse();
+		ContextConsumer<ApplicationContext> secondConsumer = (context) -> assertThat(predicate.test(24)).isFalse();
+		assertThatThrownBy(() -> firstConsumer.andThen(secondConsumer).accept(mock(ApplicationContext.class)))
+				.isInstanceOf(AssertionError.class);
+		verify(predicate).test(42);
+		verifyNoMoreInteractions(predicate);
+	}
+
+	@Test
+	void andThenWithNull() {
+		ContextConsumer<?> consumer = (context) -> {
+		};
+		assertThatIllegalArgumentException().isThrownBy(() -> consumer.andThen(null))
+				.withMessage("After must not be null");
+	}
+
+}