Hi, In https://ci.apache.org/projects/flink/flink-docs-stable/dev/local_execution.html and https://ci.apache.org/projects/flink/flink-docs-master/api/java/org/apache/flink/runtime/minicluster/MiniCluster.html I see there are 3 ways to create an execution environment for testing:
- StreamExecutionEnvironment.createLocalEnvironment and ExecutionEnvironment.createLocalEnvironment create an execution environment running on a single JVM using different threads. - CollectionEnvironment runs on a single JVM on a single thread. - I haven't found not much documentation on the Mini Cluster, but it sounds similar to the Hadoop MiniCluster <https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/CLIMiniCluster.html>. If that is then case, then it would run on many local JVMs, each of them running multiple threads. Am I correct about the Mini Cluster? Is there any additional documentation about it? I discovered it looking at the source code of AbstractTestBase, that is mentioned on https://ci.apache.org/projects/flink/flink-docs-release-1.8/dev/stream/testing.html#integration-testing. Also, it looks like launching the mini cluster registers it somewhere, so subsequent calls to `StreamExecutionEnvironment.getExecutionEnvironment` return an environment that uses the mini cluster. Is that performed by `executionEnvironment.setAsContext()` in https://github.com/apache/flink/blob/master/flink-test-utils-parent/flink-test-utils/src/main/java/org/apache/flink/test/util/MiniClusterWithClientResource.java#L56 ? Is that execution environment registration process documented anywhere? Which test execution environment is recommended for each test use case? For example I don't see why would I use CollectionEnvironment when I have the local environment available and running on several threads, what is a good use case for CollectionEnvironment? Are all these 3 environments supported equality, or maybe some of them is expected to be deprecated? Are there any additional execution environments that could be useful for testing on a single host? Thanks, Juan
