Unit Testing

As with other application styles, it is extremely important to unit test any code written as part of a batch job. The Spring core documentation covers how to unit and integration test with Spring in great detail, so it is not be repeated here. It is important, however, to think about how to “end to end” test a batch job, which is what this chapter covers. The spring-batch-test project includes classes that facilitate this end-to-end test approach.

Creating a Unit Test Class

For the unit test to run a batch job, the framework must load the job’s ApplicationContext. Two annotations are used to trigger this behavior:

@SpringJUnitConfig indicates that the class should use Spring’s JUnit facilities
@SpringBatchTest injects Spring Batch test utilities (such as the JobLauncherTestUtils and JobRepositoryTestUtils) in the test context

Note that JobRepositoryTestUtils requires a DataSource bean. Since @SpringBatchTest registers a JobRepositoryTestUtils in the test context, it is expected that the test context contains a single autowire candidate for a DataSource (either a single bean definition or one that is annotated with org.springframework.context.annotation.Primary).

The following Java example shows the annotations in use:

Using Java Configuration

@SpringBatchTest
@SpringJUnitConfig(SkipSampleConfiguration.class)
public class SkipSampleFunctionalTests { ... }

The following XML example shows the annotations in use:

Using XML Configuration

@SpringBatchTest
@SpringJUnitConfig(locations = { "/simple-job-launcher-context.xml",
                                    "/jobs/skipSampleJob.xml" })
public class SkipSampleFunctionalTests { ... }

End-To-End Testing of Batch Jobs

“End To end” testing can be defined as testing the complete run of a batch job from beginning to end. This allows for a test that sets up a test condition, executes the job, and verifies the end result.

Consider an example of a batch job that reads from the database and writes to a flat file. The test method begins by setting up the database with test data. It clears the CUSTOMER table and then inserts 10 new records. The test then launches the Job by using the launchJob() method. The launchJob() method is provided by the JobLauncherTestUtils class. The JobLauncherTestUtils class also provides the launchJob(JobParameters) method, which lets the test give particular parameters. The launchJob() method returns the JobExecution object, which is useful for asserting particular information about the Job run. In the following case, the test verifies that the Job ended with a status of COMPLETED.

The following listing shows an example with JUnit 5 in XML configuration style:

XML Based Configuration

@SpringBatchTest
@SpringJUnitConfig(locations = { "/simple-job-launcher-context.xml",
                                    "/jobs/skipSampleJob.xml" })
public class SkipSampleFunctionalTests {

    @Autowired
    private JobLauncherTestUtils jobLauncherTestUtils;

    private JdbcTemplate jdbcTemplate;

    @Autowired
    public void setDataSource(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Test
    public void testJob(@Autowired Job job) throws Exception {
        this.jobLauncherTestUtils.setJob(job);
        this.jdbcTemplate.update("delete from CUSTOMER");
        for (int i = 1; i <= 10; i++) {
            this.jdbcTemplate.update("insert into CUSTOMER values (?, 0, ?, 100000)",
                                      i, "customer" + i);
        }

        JobExecution jobExecution = jobLauncherTestUtils.launchJob();


        Assert.assertEquals("COMPLETED", jobExecution.getExitStatus().getExitCode());
    }
}

The following listing shows an example with JUnit 5 in Java configuration style:

Java Based Configuration

@SpringBatchTest
@SpringJUnitConfig(SkipSampleConfiguration.class)
public class SkipSampleFunctionalTests {

    @Autowired
    private JobLauncherTestUtils jobLauncherTestUtils;

    private JdbcTemplate jdbcTemplate;

    @Autowired
    public void setDataSource(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Test
    public void testJob(@Autowired Job job) throws Exception {
        this.jobLauncherTestUtils.setJob(job);
        this.jdbcTemplate.update("delete from CUSTOMER");
        for (int i = 1; i <= 10; i++) {
            this.jdbcTemplate.update("insert into CUSTOMER values (?, 0, ?, 100000)",
                                      i, "customer" + i);
        }

        JobExecution jobExecution = jobLauncherTestUtils.launchJob();


        Assert.assertEquals("COMPLETED", jobExecution.getExitStatus().getExitCode());
    }
}

Testing Individual Steps

For complex batch jobs, test cases in the end-to-end testing approach may become unmanageable. It these cases, it may be more useful to have test cases to test individual steps on their own. The AbstractJobTests class contains a method called launchStep, which takes a step name and runs just that particular Step. This approach allows for more targeted tests letting the test set up data for only that step and to validate its results directly. The following example shows how to use the launchStep method to load a Step by name:

JobExecution jobExecution = jobLauncherTestUtils.launchStep("loadFileStep");

Testing Step-Scoped Components

Often, the components that are configured for your steps at runtime use step scope and late binding to inject context from the step or job execution. These are tricky to test as standalone components, unless you have a way to set the context as if they were in a step execution. That is the goal of two components in Spring Batch: StepScopeTestExecutionListener and StepScopeTestUtils.

The listener is declared at the class level, and its job is to create a step execution context for each test method, as the following example shows:

@SpringJUnitConfig
@TestExecutionListeners( { DependencyInjectionTestExecutionListener.class,
    StepScopeTestExecutionListener.class })
public class StepScopeTestExecutionListenerIntegrationTests {

    // This component is defined step-scoped, so it cannot be injected unless
    // a step is active...
    @Autowired
    private ItemReader<String> reader;

    public StepExecution getStepExecution() {
        StepExecution execution = MetaDataInstanceFactory.createStepExecution();
        execution.getExecutionContext().putString("input.data", "foo,bar,spam");
        return execution;
    }

    @Test
    public void testReader() {
        // The reader is initialized and bound to the input data
        assertNotNull(reader.read());
    }

}

There are two TestExecutionListeners. One is the regular Spring Test framework, which handles dependency injection from the configured application context to inject the reader. The other is the Spring Batch StepScopeTestExecutionListener. It works by looking for a factory method in the test case for a StepExecution, using that as the context for the test method, as if that execution were active in a Step at runtime. The factory method is detected by its signature (it must return a StepExecution). If a factory method is not provided, a default StepExecution is created.

Starting from v4.1, the StepScopeTestExecutionListener and JobScopeTestExecutionListener are imported as test execution listeners if the test class is annotated with @SpringBatchTest. The preceding test example can be configured as follows:

@SpringBatchTest
@SpringJUnitConfig
public class StepScopeTestExecutionListenerIntegrationTests {

    // This component is defined step-scoped, so it cannot be injected unless
    // a step is active...
    @Autowired
    private ItemReader<String> reader;

    public StepExecution getStepExecution() {
        StepExecution execution = MetaDataInstanceFactory.createStepExecution();
        execution.getExecutionContext().putString("input.data", "foo,bar,spam");
        return execution;
    }

    @Test
    public void testReader() {
        // The reader is initialized and bound to the input data
        assertNotNull(reader.read());
    }

}

The listener approach is convenient if you want the duration of the step scope to be the execution of the test method. For a more flexible but more invasive approach, you can use the StepScopeTestUtils. The following example counts the number of items available in the reader shown in the previous example:

int count = StepScopeTestUtils.doInStepScope(stepExecution,
    new Callable<Integer>() {
      public Integer call() throws Exception {

        int count = 0;

        while (reader.read() != null) {
           count++;
        }
        return count;
    }
});

Validating Output Files

When a batch job writes to the database, it is easy to query the database to verify that the output is as expected. However, if the batch job writes to a file, it is equally important that the output be verified. Spring Batch provides a class called AssertFile to facilitate the verification of output files. The method called assertFileEquals takes two File objects (or two Resource objects) and asserts, line by line, that the two files have the same content. Therefore, it is possible to create a file with the expected output and to compare it to the actual result, as the following example shows:

private static final String EXPECTED_FILE = "src/main/resources/data/input.txt";
private static final String OUTPUT_FILE = "target/test-outputs/output.txt";

AssertFile.assertFileEquals(new FileSystemResource(EXPECTED_FILE),
                            new FileSystemResource(OUTPUT_FILE));

Mocking Domain Objects

Another common issue encountered while writing unit and integration tests for Spring Batch components is how to mock domain objects. A good example is a StepExecutionListener, as the following code snippet shows:

public class NoWorkFoundStepExecutionListener extends StepExecutionListenerSupport {

    public ExitStatus afterStep(StepExecution stepExecution) {
        if (stepExecution.getReadCount() == 0) {
            return ExitStatus.FAILED;
        }
        return null;
    }
}

The framework provides the preceding listener example and checks a StepExecution for an empty read count, thus signifying that no work was done. While this example is fairly simple, it serves to illustrate the types of problems that you may encounter when you try to unit test classes that implement interfaces requiring Spring Batch domain objects. Consider the following unit test for the listener’s in the preceding example:

private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();

@Test
public void noWork() {
    StepExecution stepExecution = new StepExecution("NoProcessingStep",
                new JobExecution(new JobInstance(1L, new JobParameters(),
                                 "NoProcessingJob")));

    stepExecution.setExitStatus(ExitStatus.COMPLETED);
    stepExecution.setReadCount(0);

    ExitStatus exitStatus = tested.afterStep(stepExecution);
    assertEquals(ExitStatus.FAILED.getExitCode(), exitStatus.getExitCode());
}

Because the Spring Batch domain model follows good object-oriented principles, the StepExecution requires a JobExecution, which requires a JobInstance and JobParameters, to create a valid StepExecution. While this is good in a solid domain model, it does make creating stub objects for unit testing verbose. To address this issue, the Spring Batch test module includes a factory for creating domain objects: MetaDataInstanceFactory. Given this factory, the unit test can be updated to be more concise, as the following example shows:

private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();

@Test
public void testAfterStep() {
    StepExecution stepExecution = MetaDataInstanceFactory.createStepExecution();

    stepExecution.setExitStatus(ExitStatus.COMPLETED);
    stepExecution.setReadCount(0);

    ExitStatus exitStatus = tested.afterStep(stepExecution);
    assertEquals(ExitStatus.FAILED.getExitCode(), exitStatus.getExitCode());
}

The preceding method for creating a simple StepExecution is only one convenience method available within the factory. You can find a full method listing in its Javadoc.