10. Unit Testing

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

10.1 Creating a Unit Test Class

In order for the unit test to run a batch job, the framework must load the job's ApplicationContext. Two annotations are used to trigger this:

  • @RunWith(SpringJUnit4ClassRunner.class) : Indicates that the class should use Spring's JUnit facilities

  • @ContextConfiguration(locations = {...}) : Indicates which XML files contain the ApplicationContext.

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "/simple-job-launcher-context.xml",
                                    "/jobs/skipSampleJob.xml" })
public class SkipSampleFunctionalTests { ... }

10.2 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.

In the example below, the batch job 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 using the launchJob() method. The launchJob () method is provided by the JobLauncherTestUtils class. Also provided by the utils class is launchJob(JobParameters) , which allows the test to give particular parameters. The launchJob() method returns the JobExecution object which is useful for asserting particular information about the Job run. In the case below, the test verifies that the Job ended with status "COMPLETED".

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "/simple-job-launcher-context.xml",
                                    "/jobs/skipSampleJob.xml" })
public class SkipSampleFunctionalTests {

    @Autowired
    private JobLauncherTestUtils jobLauncherTestUtils;

    private SimpleJdbcTemplate simpleJdbcTemplate;

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

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

        JobExecution jobExecution = jobLauncherTestUtils.launchJob().getStatus();

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

10.3 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 launchStep that takes a step name and runs just that particular Step . This approach allows for more targeted tests by allowing the test to set up data for just that step and to validate its results directly.

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

10.4 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: the StepScopeTestExecutionListener and the StepScopeTestUtils .

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

@ContextConfiguration
@TestExecutionListeners( { DependencyInjectionTestExecutionListener.class,
    StepScopeTestExecutionListener.class })
@RunWith(SpringJUnit4ClassRunner.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 getStepExection() {
        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 from the regular Spring Test framework and handles dependency injection from the configured application context, injecting the reader, and the other is the Spring Batch StepScopeTestExecutionListener . It works by looking for a factory method in the test case for a StepExecution , and using that as the context for the test method, as if that execution was active in a Step at runtime. The factory method is detected by its signature (it just has to return a StepExecution ). If a factory method is not provided then a default StepExecution is created.

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 . For example, to count the number of items available in the reader above:

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

        int count = 0;

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

10.5 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 AssertFile to facilitate the verification of output files. The method 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:

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));

10.6 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 illustrated below:

public class NoWorkFoundStepExecutionListener extends StepExecutionListenerSupport {

    public ExitStatus afterStep(StepExecution stepExecution) {
        if (stepExecution.getReadCount() == 0) {
            throw new NoWorkFoundException("Step has not processed any items");
        }
        return stepExecution.getExitStatus();
    }
}

The above listener is provided by the framework 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 may be encountered when attempting to unit test classes that implement interfaces requiring Spring Batch domain objects. Consider the above listener's unit test:

private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();

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

    stepExecution.setReadCount(0);

    try {
        tested.afterStep(stepExecution);
        fail();
    } catch (NoWorkFoundException e) {
        assertEquals("Step has not processed any items", e.getMessage());
    }
}

Because the Spring Batch domain model follows good object orientated principles, the StepExecution requires a JobExecution , which requires a JobInstance and JobParameters in order 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:

private NoWorkFoundStepExecutionListener tested = new NoWorkFoundStepExecutionListener();

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

    stepExecution.setReadCount(0);

    try {
        tested.afterStep(stepExecution);
        fail();
    } catch (NoWorkFoundException e) {
        assertEquals("Step has not processed any items", e.getMessage());
    }
}

The above method for creating a simple StepExecution is just one convenience method available within the factory. A full method listing can be found in its Javadoc.