Consider SpringBootTest's web environment in context cache key

Previously, the web environment configured on `@SpringBootTest` was not
part of the context cache key. As a result, two test classes that has
identical configuration other than one using a MOCK web environment and
the other using a DEFINED_PORT web environment would share a context
when they should not do so. Classes that use MOCK and RANDOM_PORT were
not affected as the use of RANDOM_PORT results in a property for the
port being added to the environment.

This commit adds a new ContextCustomizer, SpringBootTestWebEnvironment,
that is used to capture the `webEnvironment` from `@SpringBootTest`
and use it in its hashCode and equals implementations. This fixes the
problem as all context customizers are evaluated when determing the
equality of two context cache keys.

Fixes gh-23085

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

@@ -359,6 +359,7 @@ public class SpringBootTestContextBootstrapper extends DefaultTestContextBootstr
 			Class<?>[] classes, String[] propertySourceProperties) {
 		Set<ContextCustomizer> contextCustomizers = new LinkedHashSet<>(mergedConfig.getContextCustomizers());
 		contextCustomizers.add(new SpringBootTestArgs(mergedConfig.getTestClass()));
+		contextCustomizers.add(new SpringBootTestWebEnvironment(mergedConfig.getTestClass()));
 		return new MergedContextConfiguration(mergedConfig.getTestClass(), mergedConfig.getLocations(), classes,
 				mergedConfig.getContextInitializerClasses(), mergedConfig.getActiveProfiles(),
 				mergedConfig.getPropertySourceLocations(), propertySourceProperties, contextCustomizers,

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2012-2020 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;
+
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.annotation.MergedAnnotations;
+import org.springframework.test.context.ContextCustomizer;
+import org.springframework.test.context.MergedContextConfiguration;
+
+/**
+ * {@link ContextCustomizer} to track the web environment that is used in a
+ * {@link SpringBootTest}. The web environment is taken into account when evaluating a
+ * {@link MergedContextConfiguration} to determine if a context can be shared between
+ * tests.
+ *
+ * @author Andy Wilkinson
+ */
+class SpringBootTestWebEnvironment implements ContextCustomizer {
+
+	private final WebEnvironment webEnvironment;
+
+	SpringBootTestWebEnvironment(Class<?> testClass) {
+		this.webEnvironment = MergedAnnotations.from(testClass, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY)
+				.get(SpringBootTest.class).getValue("webEnvironment", WebEnvironment.class).orElse(null);
+	}
+
+	@Override
+	public void customizeContext(ConfigurableApplicationContext context, MergedContextConfiguration mergedConfig) {
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		return (obj != null) && (getClass() == obj.getClass())
+				&& this.webEnvironment == ((SpringBootTestWebEnvironment) obj).webEnvironment;
+	}
+
+	@Override
+	public int hashCode() {
+		return (this.webEnvironment != null) ? this.webEnvironment.hashCode() : 0;
+	}
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/bootstrap/SpringBootTestContextBootstrapperTests.java

@@ -71,6 +71,24 @@ class SpringBootTestContextBootstrapperTests {
 		assertThat(contextConfiguration).isEqualTo(otherContextConfiguration);
 	}
 
+	@Test
+	void mergedContextConfigurationWhenWebEnvironmentsDifferentShouldNotBeConsideredEqual() {
+		TestContext context = buildTestContext(SpringBootTestMockWebEnvironmentConfiguration.class);
+		Object contextConfiguration = ReflectionTestUtils.getField(context, "mergedContextConfiguration");
+		TestContext otherContext = buildTestContext(SpringBootTestDefinedPortWebEnvironmentConfiguration.class);
+		Object otherContextConfiguration = ReflectionTestUtils.getField(otherContext, "mergedContextConfiguration");
+		assertThat(contextConfiguration).isNotEqualTo(otherContextConfiguration);
+	}
+
+	@Test
+	void mergedContextConfigurationWhenWebEnvironmentsSameShouldtBeConsideredEqual() {
+		TestContext context = buildTestContext(SpringBootTestMockWebEnvironmentConfiguration.class);
+		Object contextConfiguration = ReflectionTestUtils.getField(context, "mergedContextConfiguration");
+		TestContext otherContext = buildTestContext(SpringBootTestAnotherMockWebEnvironmentConfiguration.class);
+		Object otherContextConfiguration = ReflectionTestUtils.getField(otherContext, "mergedContextConfiguration");
+		assertThat(contextConfiguration).isEqualTo(otherContextConfiguration);
+	}
+
 	@SuppressWarnings("rawtypes")
 	private TestContext buildTestContext(Class<?> testClass) {
 		SpringBootTestContextBootstrapper bootstrapper = new SpringBootTestContextBootstrapper();
@@ -99,6 +117,21 @@ class SpringBootTestContextBootstrapperTests {
 
 	}
 
+	@SpringBootTest(webEnvironment = WebEnvironment.MOCK)
+	static class SpringBootTestMockWebEnvironmentConfiguration {
+
+	}
+
+	@SpringBootTest(webEnvironment = WebEnvironment.MOCK)
+	static class SpringBootTestAnotherMockWebEnvironmentConfiguration {
+
+	}
+
+	@SpringBootTest(webEnvironment = WebEnvironment.DEFINED_PORT)
+	static class SpringBootTestDefinedPortWebEnvironmentConfiguration {
+
+	}
+
 	@SpringBootTest(args = "--app.test=same")
 	static class SpringBootTestSameArgsConfiguration {