public boolean isJoin() {
    return sourceSchemas.size() > 1;
  }
@Test
  public void shouldNotBeJoinIfSingleSchema() {
    // When:
    sourceSchemas = new SourceSchemas(ImmutableMap.of(ALIAS_1, SCHEMA_1));

    // Then:
    assertThat(sourceSchemas.isJoin(), is(false));
  }