Add Junit5 OutputCapture Extension

Closes gh-14738

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

@@ -0,0 +1,231 @@
+/*
+ * 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 java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.hamcrest.Matcher;
+import org.junit.Assert;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.api.extension.ParameterResolutionException;
+import org.junit.jupiter.api.extension.ParameterResolver;
+
+import org.springframework.boot.ansi.AnsiOutput;
+
+import static org.hamcrest.Matchers.allOf;
+
+/**
+ * JUnit5 {@code @Extension} to capture output from System.out and System.err.
+ *
+ * @author Madhura Bhave
+ */
+public class OutputCapture implements BeforeEachCallback, AfterEachCallback,
+		BeforeAllCallback, ParameterResolver, CharSequence {
+
+	private CaptureOutputStream captureOut;
+
+	private CaptureOutputStream captureErr;
+
+	private ByteArrayOutputStream methodLevelCopy;
+
+	private ByteArrayOutputStream classLevelCopy;
+
+	private List<Matcher<? super String>> matchers = new ArrayList<>();
+
+	@Override
+	public void afterEach(ExtensionContext context) {
+		try {
+			if (!this.matchers.isEmpty()) {
+				String output = this.toString();
+				Assert.assertThat(output, allOf(this.matchers));
+			}
+		}
+		finally {
+			releaseOutput();
+		}
+
+	}
+
+	@Override
+	public void beforeEach(ExtensionContext context) {
+		releaseOutput();
+		this.methodLevelCopy = new ByteArrayOutputStream();
+		captureOutput(this.methodLevelCopy);
+	}
+
+	private void captureOutput(ByteArrayOutputStream copy) {
+		AnsiOutputControl.get().disableAnsiOutput();
+		this.captureOut = new CaptureOutputStream(System.out, copy);
+		this.captureErr = new CaptureOutputStream(System.err, copy);
+		System.setOut(new PrintStream(this.captureOut));
+		System.setErr(new PrintStream(this.captureErr));
+	}
+
+	private void releaseOutput() {
+		if (this.captureOut == null) {
+			return;
+		}
+		AnsiOutputControl.get().enabledAnsiOutput();
+		System.setOut(this.captureOut.getOriginal());
+		System.setErr(this.captureErr.getOriginal());
+		this.methodLevelCopy = null;
+	}
+
+	private void flush() {
+		try {
+			this.captureOut.flush();
+			this.captureErr.flush();
+		}
+		catch (IOException ex) {
+			// ignore
+		}
+	}
+
+	@Override
+	public int length() {
+		return this.toString().length();
+	}
+
+	@Override
+	public char charAt(int index) {
+		return this.toString().charAt(index);
+	}
+
+	@Override
+	public CharSequence subSequence(int start, int end) {
+		return this.toString().subSequence(start, end);
+	}
+
+	@Override
+	public String toString() {
+		flush();
+		if (this.classLevelCopy == null && this.methodLevelCopy == null) {
+			return "";
+		}
+		StringBuilder builder = new StringBuilder();
+		if (this.classLevelCopy != null) {
+			builder.append(this.classLevelCopy.toString());
+		}
+		builder.append(this.methodLevelCopy.toString());
+		return builder.toString();
+	}
+
+	@Override
+	public void beforeAll(ExtensionContext context) {
+		this.classLevelCopy = new ByteArrayOutputStream();
+		captureOutput(this.classLevelCopy);
+	}
+
+	@Override
+	public boolean supportsParameter(ParameterContext parameterContext,
+			ExtensionContext extensionContext) throws ParameterResolutionException {
+		return OutputCapture.class.equals(parameterContext.getParameter().getType());
+	}
+
+	@Override
+	public Object resolveParameter(ParameterContext parameterContext,
+			ExtensionContext extensionContext) throws ParameterResolutionException {
+		return this;
+	}
+
+	private static class CaptureOutputStream extends OutputStream {
+
+		private final PrintStream original;
+
+		private final OutputStream copy;
+
+		CaptureOutputStream(PrintStream original, OutputStream copy) {
+			this.original = original;
+			this.copy = copy;
+		}
+
+		@Override
+		public void write(int b) throws IOException {
+			this.copy.write(b);
+			this.original.write(b);
+			this.original.flush();
+		}
+
+		@Override
+		public void write(byte[] b) throws IOException {
+			write(b, 0, b.length);
+		}
+
+		@Override
+		public void write(byte[] b, int off, int len) throws IOException {
+			this.copy.write(b, off, len);
+			this.original.write(b, off, len);
+		}
+
+		public PrintStream getOriginal() {
+			return this.original;
+		}
+
+		@Override
+		public void flush() throws IOException {
+			this.copy.flush();
+			this.original.flush();
+		}
+
+	}
+
+	/**
+	 * Allow AnsiOutput to not be on the test classpath.
+	 */
+	private static class AnsiOutputControl {
+
+		public void disableAnsiOutput() {
+		}
+
+		public void enabledAnsiOutput() {
+		}
+
+		public static AnsiOutputControl get() {
+			try {
+				Class.forName("org.springframework.boot.ansi.AnsiOutput");
+				return new AnsiPresentOutputControl();
+			}
+			catch (ClassNotFoundException ex) {
+				return new AnsiOutputControl();
+			}
+		}
+
+	}
+
+	private static class AnsiPresentOutputControl extends AnsiOutputControl {
+
+		@Override
+		public void disableAnsiOutput() {
+			AnsiOutput.setEnabled(AnsiOutput.Enabled.NEVER);
+		}
+
+		@Override
+		public void enabledAnsiOutput() {
+			AnsiOutput.setEnabled(AnsiOutput.Enabled.DETECT);
+		}
+
+	}
+
+}

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!!!");
+	}
+
+}