private static void addStreamMetadataCacheMetadata(StreamMetadataCache mockStreamMetadataCache,
      Map<SystemStream, SystemStreamMetadata> systemStreamMetadataMap) {
    scala.collection.immutable.Set<SystemStream> systemStreams =
        JavaConverters.asScalaSetConverter(systemStreamMetadataMap.keySet()).asScala().toSet();
    scala.collection.immutable.Map<SystemStream, SystemStreamMetadata> scalaSystemStreamMetadataMap =
        ScalaJavaUtil.toScalaMap(systemStreamMetadataMap);
    when(mockStreamMetadataCache.getStreamMetadata(systemStreams, true)).thenReturn(scalaSystemStreamMetadataMap);
  }
Unfortunately, we still need powermock for testing the regex topic flow, since that flow checks for a specific
rewriter class, and setting up the support for that specific class is too cumbersome.
Many of the tests do not need powermock.
samza-core/src/test/java/org/apache/samza/coordinator/TestJobModelCalculator.java