# Unit Testing

## Unit Testing

XMLJavaBoth

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

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 behavior:

* `@RunWith(SpringJUnit4ClassRunner.class)`: Indicates that the class should use Spring’s
  JUnit facilities

* `@ContextConfiguration(…​)`: Indicates which resources to configure the`ApplicationContext` with.

Starting from v4.1, it is also possible to inject Spring Batch test utilities
like the `JobLauncherTestUtils` and `JobRepositoryTestUtils` in the test context
using the `@SpringBatchTest` annotation.

|   |It should be noted that `JobLauncherTestUtils` requires a `Job` bean and that`JobRepositoryTestUtils` requires a `DataSource` bean. Since `@SpringBatchTest`registers a `JobLauncherTestUtils` and a `JobRepositoryTestUtils` in the test<br/>context, it is expected that the test context contains a single autowire candidate<br/>for a `Job` and a `DataSource` (either a single bean definition or one that is<br/>annotated with `org.springframework.context.annotation.Primary`).|
|---|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

The following Java example shows the annotations in use:

Using Java Configuration

```
@SpringBatchTest
@RunWith(SpringRunner.class)
@ContextConfiguration(classes=SkipSampleConfiguration.class)
public class SkipSampleFunctionalTests { ... }
```

The following XML example shows the annotations in use:

Using XML Configuration

```
@SpringBatchTest
@RunWith(SpringRunner.class)
@ContextConfiguration(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 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 following case, the test verifies that the `Job` ended with
status "COMPLETED".

The following listing shows the example in XML:

XML Based Configuration

```
@SpringBatchTest
@RunWith(SpringRunner.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();

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

The following listing shows the example in Java:

Java Based Configuration

```
@SpringBatchTest
@RunWith(SpringRunner.class)
@ContextConfiguration(classes=SkipSampleConfiguration.class)
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();

        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 shown in the following example:

```
@ContextConfiguration
@TestExecutionListeners( { DependencyInjectionTestExecutionListener.class,
    StepScopeTestExecutionListener.class })
@RunWith(SpringRunner.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, then 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
@RunWith(SpringRunner.class)
@ContextConfiguration
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 shown in the following example:

```
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
illustrated in the following code snippet:

```
public class NoWorkFoundStepExecutionListener extends StepExecutionListenerSupport {

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

The preceding listener example 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 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 shown in the following example:

```
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 just one convenience method
available within the factory. A full method listing can be found in its[Javadoc](https://docs.spring.io/spring-batch/apidocs/org/springframework/batch/test/MetaDataInstanceFactory.html).