String getSubstitutionVariable(String key) {
    return substitutionVariables.get(key);
  }
@Test
  public void shouldNotBeVerboseByDefault() {
    assertThat(new LoggingConfiguration(null)
      .getSubstitutionVariable(LoggingConfiguration.PROPERTY_ROOT_LOGGER_LEVEL)).isEqualTo(LoggingConfiguration.LEVEL_ROOT_DEFAULT);
  }