Add JUnit 5 ModifiedClassPathExtension

Add a JUnit 5 extension that allows tests to be run with a
modified classpath. Since JUnit 5 does not currently offer a way
to run tests with a different classpath, we instead fake the
original invocation and launch an entirely new run for each
method.

See gh-17491

spring-boot-project/spring-boot-tools/spring-boot-test-support/pom.xml

@@ -70,6 +70,10 @@
 			<groupId>org.junit.jupiter</groupId>
 			<artifactId>junit-jupiter</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.junit.platform</groupId>
+			<artifactId>junit-platform-launcher</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.mockito</groupId>
 			<artifactId>mockito-core</artifactId>

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/runner/classpath/ClassPathExclusions.java

@@ -24,8 +24,8 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Annotation used in combination with {@link ModifiedClassPathRunner} to exclude entries
- * from the classpath.
+ * Annotation used in combination with {@link ModifiedClassPathRunner} or
+ * {@link ModifiedClassPathExtension} to exclude entries from the classpath.
  *
  * @author Andy Wilkinson
  * @since 1.5.0

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/runner/classpath/ClassPathOverrides.java

@@ -23,8 +23,8 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Annotation used in combination with {@link ModifiedClassPathRunner} to override entries
- * on the classpath.
+ * Annotation used in combination with {@link ModifiedClassPathRunner} or
+ * {@link ModifiedClassPathExtension} to override entries on the classpath.
  *
  * @author Andy Wilkinson
  * @since 1.5.0

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/runner/classpath/ModifiedClassPathExtension.java

+/*
+ * 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.testsupport.runner.classpath;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.net.URLClassLoader;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.jupiter.api.extension.Extension;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.InvocationInterceptor;
+import org.junit.jupiter.api.extension.ReflectiveInvocationContext;
+import org.junit.platform.engine.discovery.DiscoverySelectors;
+import org.junit.platform.launcher.Launcher;
+import org.junit.platform.launcher.LauncherDiscoveryRequest;
+import org.junit.platform.launcher.TestPlan;
+import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
+import org.junit.platform.launcher.core.LauncherFactory;
+import org.junit.platform.launcher.listeners.SummaryGeneratingListener;
+import org.junit.platform.launcher.listeners.TestExecutionSummary;
+
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * A custom {@link Extension} that runs tests using a modified class path. Entries are
+ * excluded from the class path using {@link ClassPathExclusions @ClassPathExclusions} and
+ * overridden using {@link ClassPathOverrides @ClassPathOverrides} on the test class. A
+ * class loader is created with the customized class path and is used both to load the
+ * test class and as the thread context class loader while the test is being run.
+ *
+ * @author Christoph Dreis
+ * @since 2.2.0
+ */
+public class ModifiedClassPathExtension implements InvocationInterceptor {
+
+	@Override
+	public void interceptBeforeAllMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+		interceptInvocation(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptBeforeEachMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+		interceptInvocation(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptAfterEachMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+		interceptInvocation(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptAfterAllMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext, ExtensionContext extensionContext) throws Throwable {
+		interceptInvocation(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptTestMethod(Invocation<Void> invocation, ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+		if (isModifiedClassPathClassLoader(extensionContext)) {
+			invocation.proceed();
+			return;
+		}
+		ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
+		URLClassLoader classLoader = ModifiedClassPathClassLoaderFactory
+				.createTestClassLoader(extensionContext.getRequiredTestClass());
+		Thread.currentThread().setContextClassLoader(classLoader);
+		try {
+			fakeInvocation(invocation);
+			TestExecutionSummary summary = launchTests(invocationContext, extensionContext, classLoader);
+			if (!CollectionUtils.isEmpty(summary.getFailures())) {
+				throw summary.getFailures().get(0).getException();
+			}
+		}
+		catch (Exception ex) {
+			throw ex;
+		}
+		finally {
+			Thread.currentThread().setContextClassLoader(originalClassLoader);
+		}
+	}
+
+	private TestExecutionSummary launchTests(ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext, URLClassLoader classLoader) throws ClassNotFoundException {
+		Class<?> testClass = classLoader.loadClass(extensionContext.getRequiredTestClass().getName());
+		Method method = ReflectionUtils.findMethod(testClass, invocationContext.getExecutable().getName());
+		LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
+				.selectors(DiscoverySelectors.selectMethod(testClass, method)).build();
+		Launcher launcher = LauncherFactory.create();
+		TestPlan testPlan = launcher.discover(request);
+		SummaryGeneratingListener listener = new SummaryGeneratingListener();
+		launcher.registerTestExecutionListeners(listener);
+		launcher.execute(testPlan);
+		return listener.getSummary();
+	}
+
+	private boolean isModifiedClassPathClassLoader(ExtensionContext extensionContext) {
+		return extensionContext.getRequiredTestClass().getClassLoader().getClass().getName()
+				.equals(ModifiedClassPathClassLoader.class.getName());
+	}
+
+	private void interceptInvocation(Invocation<Void> invocation, ExtensionContext extensionContext) throws Throwable {
+		if (isModifiedClassPathClassLoader(extensionContext)) {
+			invocation.proceed();
+		}
+		else {
+			fakeInvocation(invocation);
+		}
+	}
+
+	private void fakeInvocation(Invocation invocation) {
+		try {
+			Field field = ReflectionUtils.findField(invocation.getClass(), "invoked");
+			ReflectionUtils.makeAccessible(field);
+			ReflectionUtils.setField(field, invocation, new AtomicBoolean(true));
+		}
+		catch (Throwable ignore) {
+
+		}
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/test/java/org/springframework/boot/testsupport/runner/classpath/ModifiedClassPathExtensionExclusionsTests.java

+/*
+ * 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.testsupport.runner.classpath;
+
+import org.hamcrest.Matcher;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.Matchers.isA;
+
+/**
+ * Tests for {@link ModifiedClassPathExtension} excluding entries from the class path.
+ *
+ * @author Christoph Dreis
+ */
+@ExtendWith(ModifiedClassPathExtension.class)
+@ClassPathExclusions("hibernate-validator-*.jar")
+class ModifiedClassPathExtensionExclusionsTests {
+
+	private static final String EXCLUDED_RESOURCE = "META-INF/services/" + "javax.validation.spi.ValidationProvider";
+
+	@Test
+	void entriesAreFilteredFromTestClassClassLoader() {
+		assertThat(getClass().getClassLoader().getResource(EXCLUDED_RESOURCE)).isNull();
+	}
+
+	@Test
+	void entriesAreFilteredFromThreadContextClassLoader() {
+		assertThat(Thread.currentThread().getContextClassLoader().getResource(EXCLUDED_RESOURCE)).isNull();
+	}
+
+	@Test
+	void testsThatUseHamcrestWorkCorrectly() {
+		Matcher<IllegalStateException> matcher = isA(IllegalStateException.class);
+		assertThat(matcher.matches(new IllegalStateException())).isTrue();
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/test/java/org/springframework/boot/testsupport/runner/classpath/ModifiedClassPathExtensionOverridesTests.java

+/*
+ * 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.testsupport.runner.classpath;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.util.StringUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ModifiedClassPathExtension} overriding entries on the class path.
+ *
+ * @author Christoph Dreis
+ */
+@ExtendWith(ModifiedClassPathExtension.class)
+@ClassPathOverrides("org.springframework:spring-context:4.1.0.RELEASE")
+class ModifiedClassPathExtensionOverridesTests {
+
+	@Test
+	void classesAreLoadedFromOverride() {
+		assertThat(ApplicationContext.class.getProtectionDomain().getCodeSource().getLocation().toString())
+				.endsWith("spring-context-4.1.0.RELEASE.jar");
+	}
+
+	@Test
+	void classesAreLoadedFromTransitiveDependencyOfOverride() {
+		assertThat(StringUtils.class.getProtectionDomain().getCodeSource().getLocation().toString())
+				.endsWith("spring-core-4.1.0.RELEASE.jar");
+	}
+
+}