Improve @SpringBatchTest to autowire the job under test in JobLauncherTestUtils if it is unique

Issue #4218

spring-batch-test/src/main/java/org/springframework/batch/test/context/BatchTestContextBeanPostProcessor.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 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.batch.test.context;
+
+import org.springframework.batch.core.Job;
+import org.springframework.batch.test.JobLauncherTestUtils;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+
+/**
+ * {@link BeanPostProcessor} implementation that injects a job bean into
+ * {@link JobLauncherTestUtils} if there is a unique job bean.
+ *
+ * @author Henning Pöttker
+ * @since 5.0
+ */
+public class BatchTestContextBeanPostProcessor implements BeanPostProcessor {
+
+	private ObjectProvider<Job> jobProvider;
+
+	@Autowired
+	public void setJobProvider(ObjectProvider<Job> jobProvider) {
+		this.jobProvider = jobProvider;
+	}
+
+	@Override
+	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+		if (bean instanceof JobLauncherTestUtils jobLauncherTestUtils) {
+			jobProvider.ifUnique(jobLauncherTestUtils::setJob);
+		}
+		return bean;
+	}
+
+}

spring-batch-test/src/main/java/org/springframework/batch/test/context/BatchTestContextCustomizer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2018-2021 the original author or authors.
+ * Copyright 2018-2022 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.
@@ -39,6 +39,8 @@ public class BatchTestContextCustomizer implements ContextCustomizer {
 
 	private static final String JOB_REPOSITORY_TEST_UTILS_BEAN_NAME = "jobRepositoryTestUtils";
 
+	private static final String BATCH_TEST_CONTEXT_BEAN_POST_PROCESSOR_BEAN_NAME = "batchTestContextBeanPostProcessor";
+
 	@Override
 	public void customizeContext(ConfigurableApplicationContext context, MergedContextConfiguration mergedConfig) {
 		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
@@ -50,6 +52,8 @@ public class BatchTestContextCustomizer implements ContextCustomizer {
 				new RootBeanDefinition(JobLauncherTestUtils.class));
 		registry.registerBeanDefinition(JOB_REPOSITORY_TEST_UTILS_BEAN_NAME,
 				new RootBeanDefinition(JobRepositoryTestUtils.class));
+		registry.registerBeanDefinition(BATCH_TEST_CONTEXT_BEAN_POST_PROCESSOR_BEAN_NAME,
+				new RootBeanDefinition(BatchTestContextBeanPostProcessor.class));
 	}
 
 	@Override

spring-batch-test/src/test/java/org/springframework/batch/test/SpringBatchTestJUnit4Tests.java

@@ -69,9 +69,6 @@ public class SpringBatchTestJUnit4Tests {
 	@Autowired
 	private ItemReader<String> jobScopedItemReader;
 
-	@Autowired
-	private Job jobUnderTest;
-
 	@Before
 	public void setUp() {
 		this.jobRepositoryTestUtils.removeJobExecutions();
@@ -105,9 +102,6 @@ public class SpringBatchTestJUnit4Tests {
 
 	@Test
 	public void testJob() throws Exception {
-		// given
-		this.jobLauncherTestUtils.setJob(this.jobUnderTest);
-
 		// when
 		JobExecution jobExecution = this.jobLauncherTestUtils.launchJob();
 

spring-batch-test/src/test/java/org/springframework/batch/test/SpringBatchTestJUnit5Tests.java

@@ -19,7 +19,6 @@ import java.util.Arrays;
 
 import javax.sql.DataSource;
 
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -72,8 +71,7 @@ public class SpringBatchTestJUnit5Tests {
 	private ItemReader<String> jobScopedItemReader;
 
 	@BeforeEach
-	void setup(@Autowired Job jobUnderTest) {
-		this.jobLauncherTestUtils.setJob(jobUnderTest);
+	void setup() {
 		this.jobRepositoryTestUtils.removeJobExecutions();
 	}
 

spring-batch-test/src/test/java/org/springframework/batch/test/context/BatchTestContextBeanPostProcessorTest.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2022 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.batch.test.context;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.batch.core.Job;
+import org.springframework.batch.core.JobExecution;
+import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
+import org.springframework.batch.test.JobLauncherTestUtils;
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
+import org.springframework.jdbc.support.JdbcTransactionManager;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * @author Henning Pöttker
+ */
+class BatchTestContextBeanPostProcessorTest {
+
+	private GenericApplicationContext applicationContext;
+
+	@BeforeEach
+	void setUp() {
+		applicationContext = new AnnotationConfigApplicationContext(BatchConfiguration.class);
+		applicationContext.registerBean(JobLauncherTestUtils.class);
+	}
+
+	@AfterEach
+	void tearDown() {
+		if (applicationContext != null) {
+			applicationContext.close();
+		}
+	}
+
+	@Test
+	void testContextWithoutJobBean() {
+		var jobLauncherTestUtils = applicationContext.getBean(JobLauncherTestUtils.class);
+		assertNotNull(jobLauncherTestUtils);
+		assertNull(jobLauncherTestUtils.getJob());
+	}
+
+	@Test
+	void testContextWithUniqueJobBean() {
+		applicationContext.registerBean(MockJob.class);
+		var jobLauncherTestUtils = applicationContext.getBean(JobLauncherTestUtils.class);
+		assertNotNull(jobLauncherTestUtils.getJob());
+	}
+
+	@Test
+	void testContextWithTwoJobBeans() {
+		applicationContext.registerBean("jobA", MockJob.class);
+		applicationContext.registerBean("jobB", MockJob.class);
+		var jobLauncherTestUtils = applicationContext.getBean(JobLauncherTestUtils.class);
+		assertNotNull(jobLauncherTestUtils);
+		assertNull(jobLauncherTestUtils.getJob());
+	}
+
+	static class MockJob implements Job {
+
+		@Override
+		public String getName() {
+			return "name";
+		}
+
+		@Override
+		public void execute(JobExecution execution) {
+		}
+
+	}
+
+	@Configuration
+	@EnableBatchProcessing
+	static class BatchConfiguration {
+
+		@Bean
+		DataSource dataSource() {
+			return new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.HSQL)
+					.addScript("/org/springframework/batch/core/schema-drop-hsqldb.sql")
+					.addScript("/org/springframework/batch/core/schema-hsqldb.sql").build();
+		}
+
+		@Bean
+		JdbcTransactionManager transactionManager(DataSource dataSource) {
+			return new JdbcTransactionManager(dataSource);
+		}
+
+		@Bean
+		BatchTestContextBeanPostProcessor beanPostProcessor() {
+			return new BatchTestContextBeanPostProcessor();
+		}
+
+	}
+
+}

spring-batch-test/src/test/java/org/springframework/batch/test/context/BatchTestContextCustomizerTests.java

@@ -46,6 +46,7 @@ class BatchTestContextCustomizerTests {
 		// then
 		assertTrue(context.containsBean("jobLauncherTestUtils"));
 		assertTrue(context.containsBean("jobRepositoryTestUtils"));
+		assertTrue(context.containsBean("batchTestContextBeanPostProcessor"));
 	}
 
 	@Test

spring-batch-test/src/test/java/org/springframework/batch/test/observability/ObservabilitySampleStepTests.java

@@ -25,7 +25,6 @@ import io.micrometer.observation.ObservationRegistry;
 import io.micrometer.tracing.test.SampleTestRunner;
 import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
 
 import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.Job;
@@ -71,11 +70,6 @@ class ObservabilitySampleStepTests extends SampleTestRunner {
 		return this.observationRegistry;
 	}
 
-	@BeforeEach
-	void setup(@Autowired Job job) {
-		this.jobLauncherTestUtils.setJob(job);
-	}
-
 	@AfterEach
 	@Override
 	protected void closeMeterRegistry() {