Replace TestSourcesPlugin with Gradle test fixture support

Prior to this series of commits, the Spring Framework build used a
custom TestSourcesPlugin to share test utilities and fixtures between
projects. This plugin served its purpose; however, it also had its
drawbacks:

- All test code was visible in all other (downstream) projects, and that
  made it too easy to introduce unnecessary coupling. For example,
  this made it more difficult to migrate to JUnit Jupiter.

This commit addresses such issues by migrating to Gradle's first-class
support for "Java test fixtures".

- Having test fixture code in a dedicated source folder makes it
  readily apparent that the code is reused across the test suite.
- The build is now much cleaner since projects explicitly declare that
  they rely on specific test fixtures of upstream projects.
- Incremental builds are now much faster on average since downstream
  projects no longer have to be recompiled due to changes in tests in
  upstream projects.
- Prior to these commits we effectively had around 20 test fixture
  dependencies. With these commits we effectively now have only 7 test
  fixture dependencies (i.e., projects that share test fixtures).

Closes gh-23550

Author: sbrannen

build.gradle

@@ -308,6 +308,7 @@ configure([rootProject] + javaProjects) { project ->
 	group = "org.springframework"
 
 	apply plugin: "java"
+	apply plugin: "java-test-fixtures"
 	apply plugin: "checkstyle"
 	apply plugin: 'org.springframework.build.compile'
 	apply from: "${rootDir}/gradle/ide.gradle"

buildSrc/README.md

@@ -1,4 +1,4 @@
-# Spring Framework build
+# Spring Framework Build
 
 This folder contains the custom plugins and conventions for the Spring Framework build.
 They are declared in the `build.gradle` file in this folder.
@@ -7,8 +7,8 @@ They are declared in the `build.gradle` file in this folder.
 
 ### Compiler conventions
 
-The `org.springframework.build.compile` applies the Java compiler conventions to the build.
-By default, the build is compiling sources with the `1.8` source and target compatibility.
+The `org.springframework.build.compile` plubin applies the Java compiler conventions to the build.
+By default, the build compiles sources with Java `1.8` source and target compatibility.
 You can test a different source compatibility version on the CLI with a project property like:
 
 ```
@@ -25,17 +25,11 @@ but doesn't affect the classpath of dependent projects.
 This plugin does not provide a `provided` configuration, as the native `compileOnly` and `testCompileOnly`
 configurations are preferred.
 
-## Test sources
-
-The `org.springframework.build.test-sources` updates `testCompile` dependencies to include
-the test source sets of `project()` dependencies. This plugin is used in the Spring Framework build 
-to share test utilities and fixtures amongst modules.
-
 ## API Diff
 
 This plugin uses the [Gradle JApiCmp](https://github.com/melix/japicmp-gradle-plugin) plugin
 to generate API Diff reports for each Spring Framework module. This plugin is applied once on the root
-project and create tasks in each framework module. Unlike previous versions of this part of the build,
+project and creates tasks in each framework module. Unlike previous versions of this part of the build,
 there is no need for checking out a specific tag. The plugin will fetch the JARs we want to compare the
 current working version with. You can generate the reports for all modules or a single module:
 
@@ -44,4 +38,4 @@ current working version with. You can generate the reports for all modules or a
 ./gradlew :spring-core:apiDiff -PbaselineVersion=5.1.0.RELEASE
 ```      
 
-The reports are located under `build/reports/api-diff/$OLDVERSION_to_$NEWVERSION/`.
+The reports are located under `build/reports/api-diff/$OLDVERSION_to_$NEWVERSION/`.

buildSrc/build.gradle

@@ -26,9 +26,5 @@ gradlePlugin {
 			id = "org.springframework.build.optional-dependencies"
 			implementationClass = "org.springframework.build.optional.OptionalDependenciesPlugin"
 		}
-		testSourcesPlugin {
-			id = "org.springframework.build.test-sources"
-			implementationClass = "org.springframework.build.testsources.TestSourcesPlugin"
-		}
 	}
 }

buildSrc/src/main/java/org/springframework/build/testsources/TestSourcesPlugin.java

@@ -1,6 +1,5 @@
 apply plugin: 'org.springframework.build.compile'
 apply plugin: 'org.springframework.build.optional-dependencies'
-apply plugin: 'org.springframework.build.test-sources'
 apply from: "$rootDir/gradle/publications.gradle"
 
 jar {
@@ -56,6 +55,14 @@ task javadocJar(type: Jar) {
 publishing {
 	publications {
 		mavenJava(MavenPublication) {
+			// Disable publication of test fixture artifacts.
+			//
+			// Once we upgrade to Gradle 6.x, we will need to delete the following line ...
+			components.java.variants.removeAll { it.outgoingConfiguration.name.startsWith("testFixtures") }
+			// ... and uncomment the following two lines.
+			// components.java.withVariantsFromConfiguration(configurations.testFixturesApiElements) { skip() }
+			// components.java.withVariantsFromConfiguration(configurations.testFixturesRuntimeElements) { skip() }
+
 			from components.java
 			artifact sourcesJar
 			artifact javadocJar

gradle/spring-module.gradle

@@ -1,12 +1,14 @@
 description = "Spring Integration Tests"
 
-apply plugin: "org.springframework.build.test-sources"
-
 dependencies {
 	testCompile(project(":spring-aop"))
 	testCompile(project(":spring-beans"))
 	testCompile(project(":spring-context"))
 	testCompile(project(":spring-core"))
+	testCompile(testFixtures(project(":spring-aop")))
+	testCompile(testFixtures(project(":spring-beans")))
+	testCompile(testFixtures(project(":spring-core")))
+	testCompile(testFixtures(project(":spring-tx")))
 	testCompile(project(":spring-expression"))
 	testCompile(project(":spring-jdbc"))
 	testCompile(project(":spring-orm"))

integration-tests/integration-tests.gradle

@@ -21,12 +21,12 @@
 import org.springframework.aop.framework.Advised;
 import org.springframework.aop.support.AopUtils;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.testfixture.beans.ITestBean;
+import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.core.testfixture.io.SerializationTestUtils;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpSession;
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
-import org.springframework.tests.sample.beans.ITestBean;
-import org.springframework.tests.sample.beans.TestBean;
-import org.springframework.util.SerializationTestUtils;
 import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.context.request.ServletRequestAttributes;
 

integration-tests/src/test/java/org/springframework/aop/config/AopNamespaceHandlerScopeIntegrationTests.java

@@ -26,17 +26,17 @@
 
 import org.springframework.aop.support.AopUtils;
 import org.springframework.aop.support.StaticMethodMatcherPointcutAdvisor;
+import org.springframework.aop.testfixture.advice.CountingBeforeAdvice;
+import org.springframework.aop.testfixture.advice.MethodCounter;
+import org.springframework.aop.testfixture.interceptor.NopInterceptor;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.beans.testfixture.beans.ITestBean;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import org.springframework.lang.Nullable;
-import org.springframework.tests.aop.advice.CountingBeforeAdvice;
-import org.springframework.tests.aop.advice.MethodCounter;
-import org.springframework.tests.aop.interceptor.NopInterceptor;
-import org.springframework.tests.sample.beans.ITestBean;
-import org.springframework.tests.transaction.CallCountingTransactionManager;
 import org.springframework.transaction.NoTransactionException;
 import org.springframework.transaction.interceptor.TransactionInterceptor;
+import org.springframework.transaction.testfixture.CallCountingTransactionManager;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

integration-tests/src/test/java/org/springframework/aop/framework/autoproxy/AdvisorAutoProxyCreatorIntegrationTests.java

@@ -28,19 +28,19 @@
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.testfixture.EnabledForTestGroups;
 import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.stereotype.Repository;
-import org.springframework.tests.EnabledForTestGroups;
-import org.springframework.tests.transaction.CallCountingTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.EnableTransactionManagement;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.testfixture.CallCountingTransactionManager;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.mockito.Mockito.mock;
-import static org.springframework.tests.TestGroup.PERFORMANCE;
+import static org.springframework.core.testfixture.TestGroup.PERFORMANCE;
 
 /**
  * Integration tests cornering bug SPR-8651, which revealed that @Scheduled methods may

integration-tests/src/test/java/org/springframework/scheduling/annotation/ScheduledAndTransactionalAnnotationIntegrationTests.java

@@ -40,9 +40,9 @@
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
 import org.springframework.stereotype.Repository;
-import org.springframework.tests.transaction.CallCountingTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.interceptor.BeanFactoryTransactionAttributeSourceAdvisor;
+import org.springframework.transaction.testfixture.CallCountingTransactionManager;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;

integration-tests/src/test/java/org/springframework/transaction/annotation/EnableTransactionManagementIntegrationTests.java

@@ -11,19 +11,19 @@
 
 	<bean id="advice" class="org.springframework.aop.interceptor.DebugInterceptor"/>
 
-	<bean id="testBean" class="org.springframework.tests.sample.beans.TestBean"/>
+	<bean id="testBean" class="org.springframework.beans.testfixture.beans.TestBean"/>
 
-	<bean id="singletonScoped" class="org.springframework.tests.sample.beans.TestBean">
+	<bean id="singletonScoped" class="org.springframework.beans.testfixture.beans.TestBean">
 		<aop:scoped-proxy/>
 		<property name="name" value="Rob Harrop"/>
 	</bean>
 
-	<bean id="requestScoped" class="org.springframework.tests.sample.beans.TestBean" scope="request">
+	<bean id="requestScoped" class="org.springframework.beans.testfixture.beans.TestBean" scope="request">
 		<aop:scoped-proxy/>
 		<property name="name" value="Rob Harrop"/>
 	</bean>
 
-	<bean id="sessionScoped" name="sessionScopedAlias" class="org.springframework.tests.sample.beans.TestBean" scope="session">
+	<bean id="sessionScoped" name="sessionScopedAlias" class="org.springframework.beans.testfixture.beans.TestBean" scope="session">
 		<aop:scoped-proxy proxy-target-class="false"/>
 		<property name="name" value="Rob Harrop"/>
 	</bean>

integration-tests/src/test/resources/org/springframework/aop/config/AopNamespaceHandlerScopeIntegrationTests-context.xml

@@ -34,7 +34,7 @@
 	</bean>
 
 	<!-- Often we can leave the definition of such infrastructural beans to child factories -->
-	<bean id="txManager" class="org.springframework.tests.transaction.CallCountingTransactionManager"/>
+	<bean id="txManager" class="org.springframework.transaction.testfixture.CallCountingTransactionManager"/>
 
 	<bean id="tas" class="org.springframework.transaction.interceptor.NameMatchTransactionAttributeSource">
 		<property name="properties">
@@ -74,20 +74,20 @@
 
 	<!-- These two beans would otherwise be eligible for autoproxying -->
 
-	<bean id="singletonDependency" class="org.springframework.tests.sample.beans.TestBean" scope="singleton"/>
+	<bean id="singletonDependency" class="org.springframework.beans.testfixture.beans.TestBean" scope="singleton"/>
 
-	<bean id="prototypeDependency" class="org.springframework.tests.sample.beans.TestBean" scope="prototype"/>
+	<bean id="prototypeDependency" class="org.springframework.beans.testfixture.beans.TestBean" scope="prototype"/>
 
 	<!-- ====== End test for prototype definitions to try to provoke circular references ========================= -->
 
 	<bean class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">
 		<property name="advice"><ref bean="countingAdvice"/></property>
-		<property name="pattern"><value>org.springframework.tests.sample.beans.ITestBean.getName</value></property>
+		<property name="pattern"><value>org.springframework.beans.testfixture.beans.ITestBean.getName</value></property>
 	</bean>
 
-	<bean id="countingAdvice" class="org.springframework.tests.aop.advice.CountingAfterReturningAdvice"/>
+	<bean id="countingAdvice" class="org.springframework.aop.testfixture.advice.CountingAfterReturningAdvice"/>
 
-	<bean id="test" class="org.springframework.tests.sample.beans.TestBean">
+	<bean id="test" class="org.springframework.beans.testfixture.beans.TestBean">
 		<property name="age"><value>4</value></property>
 	</bean>
 
@@ -97,7 +97,7 @@
 
 	<!-- The following beans test whether auto-proxying falls over for a null value -->
 
-	<bean id="tb" class="org.springframework.tests.sample.beans.TestBean"/>
+	<bean id="tb" class="org.springframework.beans.testfixture.beans.TestBean"/>
 
 	<bean id="nullValueReturned" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
 		<property name="targetObject" ref="tb"/>

integration-tests/src/test/resources/org/springframework/aop/framework/autoproxy/AdvisorAutoProxyCreatorIntegrationTests-context.xml

@@ -6,4 +6,7 @@ dependencies {
 	optional("org.aspectj:aspectjweaver")
 	optional("org.apache.commons:commons-pool2")
 	optional("com.jamonapi:jamon")
+	testCompile(testFixtures(project(":spring-beans")))
+	testCompile(testFixtures(project(":spring-core")))
+	testFixturesImplementation(testFixtures(project(":spring-core")))
 }