Build a flink-connector-kafka-0.9 test-jar

[scosenza]

Build a test-jar of flink-connector-kafka-0.9 so that Flink users can use KafkaTestEnvironmentImpl to write end to end integration tests of their Flink jobs.

[scosenza]

/cc @jgrier

[rmetzger]

Hi,
thank you for opening a pull request about this. I think the change is good to merge. One thing I'm wondering is: why do you only include on class (or a set of classes with a shared prefix) into the test-jar?
I would put all test classes into the test-jar (we never know what users will need in the future)

[scosenza]

Hi Robert,

Typically, a test-jar would not contain JUnit test classes unless they are designed to be extended. On a related note, it's also good to avoid including logback-test.xml inside your test-jars, as this leads to the following warning when others (who are also using logback) depend on your test-jar.

16:01:09,771 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Found resource [logback-test.xml] at [file:/Users/.../target/test-classes/logback-test.xml]
16:01:09,772 |-WARN in ch.qos.logback.classic.LoggerContext[default] - Resource [logback-test.xml] occurs multiple times on the classpath.
16:01:09,772 |-WARN in ch.qos.logback.classic.LoggerContext[default] - Resource [logback-test.xml] occurs at [jar:file:/Users/scosenza/.m2/repository/org/apache/flink/flink-connector-kafka-base_2.11/1.0.2/flink-connector-kafka-base_2.11-1.0.2-tests.jar!/logback-test.xml]
16:01:09,772 |-WARN in ch.qos.logback.classic.LoggerContext[default] - Resource [logback-test.xml] occurs at [jar:file:/Users/scosenza/.m2/repository/org/apache/flink/flink-core/1.0.2/flink-core-1.0.2-tests.jar!/logback-test.xml]
16:01:09,772 |-WARN in ch.qos.logback.classic.LoggerContext[default] - Resource [logback-test.xml] occurs at [file:/Users/scosenza/.../target/test-classes/logback-test.xml]
16:01:09,772 |-WARN in ch.qos.logback.classic.LoggerContext[default] - Resource [logback-test.xml] occurs at [jar:file:/Users/scosenza/.m2/repository/org/apache/flink/flink-runtime_2.11/1.0.2/flink-runtime_2.11-1.0.2-tests.jar!/logback-test.xml]

[StephanEwen]

I think this is good, will merge this...