[FLINK-14335] ExampleIntegrationTest in testing docs is incorrect

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.9.0
• Fix Version/s: 1.9.2, 1.10.0
• Component/s: Documentation, Tests
• Labels: pull-request-available
• Assignee: Yangze Guo
• Reporter: Chesnay Schepler
• Created: 07/Oct/19 09:15
• Updated: 29/Jan/20 09:33
• Resolved: 09/Oct/19 08:28

Description

The java version of the ExampleIntegrationTest is incorrect since it assumes elements to arrive in the sink in order, but this isn't guaranteed since there are 2 sink subtasks mutating a shared collection.

The scala example was modified correctly; it checks that elements are contained without verifying the order.

public class ExampleIntegrationTest {
        ...

        // configure your test environment
        env.setParallelism(2);

        ...

        // create a stream of custom elements and apply transformations
        env.fromElements(1L, 21L, 22L)
                .map(new IncrementMapFunction())
                .addSink(new CollectSink());

        // execute
        env.execute();

        // verify your results
        assertEquals(Lists.newArrayList(2L, 42L, 44L), CollectSink.values);
    }

    // create a testing sink
    private static class CollectSink implements SinkFunction<Long> {

        // must be static
        public static final List<Long> values = new ArrayList<>();

        @Override
        public synchronized void invoke(Long value) throws Exception {
            values.add(value);
        }
    }
}

Issue Links

• is caused by: FLINK-12508 Expand Documentation on Testing DataStream API programs
• links to: GitHub Pull Request #9862