private static Config addSystemStreamInput(SystemStream systemStream, Config config) {
    String existingInputs = config.get(TaskConfig.INPUT_STREAMS);
    Preconditions.checkArgument(StringUtils.isNotEmpty(existingInputs));
    Map<String, String> newConfig = new HashMap<>(config);
    newConfig.put(TaskConfig.INPUT_STREAMS, String.format("%s,%s", existingInputs, taskInputString(systemStream)));
    return new MapConfig(newConfig);
  }
Groups all SSPs into two tasks. The first task gets all of the SSPs with a partition id of 0. The second task gets
all other SSPs. This is used for testing a custom {@link SystemStreamPartitionGrouper}.
samza-core/src/test/java/org/apache/samza/coordinator/TestJobModelCalculator.java