The sequencing framework was designed to make testing sequencers much easier. In particular, the StreamSequencer interface does not make use of the JCR API. So instead of requiring a fully-configured JCR repository and JBoss DNA system, unit tests for a sequencer can focus on testing that the content is processed correctly and the desired output graph is generated.

The following code fragment shows one way of testing a sequencer, using JUnit 4.4 assertions and some of the classes made available by JBoss DNA. Of course, this example code does not do any error handling and does not make all the assertions a real test would.

Sequencer sequencer = new ImageMetadataSequencer();
MockSequencerOutput output = new MockSequencerOutput();
ProgressMonitor progress = new SimpleProgressMonitor("Test activity");
InputStream stream = null;
try {
    stream = this.getClass().getClassLoader().getResource("caution.gif").openStream();
    sequencer.sequence(stream,output,progress);   // writes to 'output'
    assertThat(output.getPropertyValues("image:metadata", "jcr:primaryType"), 
               is(new Object[] {"image:metadata"}));
    assertThat(output.getPropertyValues("image:metadata", "jcr:mimeType"), 
               is(new Object[] {"image/gif"}));
    // ... make more assertions here
    assertThat(output.hasReferences(), is(false));
} finally {
    stream.close();
}

It's also useful to test that a sequencer produces no output for something it should not understand:

Sequencer sequencer = new ImageMetadataSequencer();
MockSequencerOutput output = new MockSequencerOutput();
ProgressMonitor progress = new SimpleProgressMonitor("Test activity");
InputStream stream = null;
try {
    stream = this.getClass().getClassLoader().getResource("caution.pict").openStream();
    sequencer.sequence(stream,output,progress);   // writes to 'output'
    assertThat(output.hasProperties(), is(false));
    assertThat(output.hasReferences(), is(false));
} finally {
    stream.close();
}

These are just two simple tests that show ways of testing a sequencer. Some tests may get quite involved, especially if a lot of output data are produced.