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From Stephan Ewen <se...@apache.org>
Subject Re: Unit testing Flink programs / DataSet operations
Date Wed, 05 Nov 2014 12:53:02 GMT
Hey!

Why don't you simply run this program and verify that the result is 6?

You can use the "LocalCollectionOutputFormat" to collect the results (in
your case the one value) and compare it.

Stephan



On Wed, Nov 5, 2014 at 1:44 PM, Viktor Rosenfled <
viktor.rosenfeld@tu-berlin.de> wrote:

> Hi everybody,
>
> I have the following test case prototype and I want to verify that sum()
> actually computes the sum.
>
>     @Test
>     public void shouldComputeSum() throws Exception {
>         // given
>         ExecutionEnvironment env =
> ExecutionEnvironment.getExecutionEnvironment();
>         DataSet<Tuple1&lt;Long>> input = env.fromElements(
>                 new Tuple1<Long>(1L),
>                 new Tuple1<Long>(2L),
>                 new Tuple1<Long>(3L));
>
>         // when
>         DataSet<Tuple1&lt;Long>> result = input.sum(0);
>
>         // then
>         // verify that result is 6
>     }
>
> I found AggregateTranslationTest where a program plan is created and then
> the sink is accessed to verify some structure on the output operator. Using
> this as a starting point, I wrote the following code:
>
>         // verify that the result is 6
>         OutputFormat<Tuple1&lt;Long>> outputFormat =
> mock(OutputFormat.class, withSettings().serializable());
>         output.output(outputFormat);
>         env.execute("ComputeCountTest");
>         verify(outputFormat).writeRecord(new Tuple1<Long>(6L));
>
> I encountered a few problems:
>
> - I can't run this test code from the flink-java module because
> env.execute() requires flink-clients which leads to a circular dependency.
>
> - The outputFormat needs to be serializable; luckily Mockito supports this
> even though they consider it a code smell but that can be argued.
>
> - It doesn't actually work. Mockito prints:
>
>     Wanted but not invoked:
>     outputFormat.writeRecord((6));
>     -> at
>
> org.apache.flink.api.java.operator.MyAggregateOperatorTest.shouldComputeSum(MyAggregateOperatorTest.java:31)
>     Actually, there were zero interactions with this mock.
>
> I suspect env.execute() is non-blocking and that there's a race condition.
>
> Executing a whole Flink program is probably too heavyweight for a unit test
> but I wanted to use it as a starting point. I also found two other methods
> to test operator code but I'm not sure which is the preferred way:
>
> - MapTest: invokes a Map operator on a collection using
> MockInvokable.createAndExecute()
>
> - MapOperatorTest: invokes a Map operator op on a collection using
> op.executeOnCollection()
>
> So, my question is basically if there's a best practice in the Flink code
> base to write a unit test similar to the one above.
>
> Best,
> Viktor
>
>
>
> --
> View this message in context:
> http://apache-flink-incubator-mailing-list-archive.1008284.n3.nabble.com/Unit-testing-Flink-programs-DataSet-operations-tp2371.html
> Sent from the Apache Flink (Incubator) Mailing List archive. mailing list
> archive at Nabble.com.
>

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