Add Junit5 OutputCapture Extension

Closes gh-14738

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/extension/OutputCaptureExtendWithTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2019 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.extension;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.ExtensionContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link OutputCapture} when used via {@link ExtendWith}.
+ *
+ * @author Madhura Bhave
+ */
+@ExtendWith(OutputCapture.class)
+@ExtendWith(OutputCaptureExtendWithTests.BeforeAllExtension.class)
+public class OutputCaptureExtendWithTests {
+
+	@Test
+	void captureShouldReturnOutputCapturedBeforeTestMethod(OutputCapture output) {
+		assertThat(output).contains("Before all");
+		assertThat(output).doesNotContain("Hello");
+	}
+
+	@Test
+	void captureShouldReturnAllCapturedOutput(OutputCapture output) {
+		System.out.println("Hello World");
+		System.err.println("Error!!!");
+		assertThat(output).contains("Before all");
+		assertThat(output).contains("Hello World");
+		assertThat(output).contains("Error!!!");
+	}
+
+	static class BeforeAllExtension implements BeforeAllCallback {
+
+		@Override
+		public void beforeAll(ExtensionContext context) {
+			System.out.println("Before all");
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/extension/OutputCaptureRegisterExtensionTests.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2019 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.extension;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link OutputCapture} when used via {@link RegisterExtension}.
+ *
+ * @author Madhura Bhave
+ */
+public class OutputCaptureRegisterExtensionTests {
+
+	@RegisterExtension
+	OutputCapture output = new OutputCapture();
+
+	@Test
+	void captureShouldReturnAllCapturedOutput() {
+		System.out.println("Hello World");
+		System.err.println("Error!!!");
+		assertThat(this.output).contains("Hello World");
+		assertThat(this.output).contains("Error!!!");
+	}
+
+}