public LogicalSchema resolve(final ExecutionStep<?> step, final LogicalSchema schema) {
    return Optional.ofNullable(HANDLERS.get(step.getClass()))
        .map(h -> h.handle(this, schema, step))
        .orElseThrow(() -> new IllegalStateException("Unhandled step class: " + step.getClass()));
  }
@Test
  public void shouldResolveSchemaForStreamGroupByKey() {
    // Given:
    final StreamGroupByKey step = new StreamGroupByKey(
        PROPERTIES,
        streamSource,
        formats
    );

    // When:
    final LogicalSchema result = resolver.resolve(step, SCHEMA);

    // Then:
    assertThat(result, is(SCHEMA));
  }