@Override
    public C removeConfiguration(String configName) {
        if (configName.equals(DEFAULT_CONFIG)) {
            throw new IllegalArgumentException(
                "You cannot remove the default configuration");
        }
        return this.configurations.remove(configName);
    }
@Test
    public void shouldNotAllowToRemoveDefaultConfiguration() {
        TestRegistry testRegistry = new TestRegistry();

        assertThatThrownBy(() -> testRegistry.removeConfiguration("default"))
            .isInstanceOf(IllegalArgumentException.class);
    }