### Question:
SystemPropertiesConfig implements Config { @Override public boolean isDefaultMethodsEnabled() { return Boolean.parseBoolean(p.getProperty(DEFAULT_METHODS, "false")); } SystemPropertiesConfig(Properties p); boolean isFullyConfigured(); @Override int getBytecodeVersion(); @Override boolean isDefaultMethodsEnabled(); @Override Path getInputDir(); @Override Path getOutputDir(); @Override List<Path> getClasspath(); @Override List<Path> getIncludedFiles(); @Override boolean isJavacHacksEnabled(); @Override boolean isQuiet(); String getHelp();  }### Answer:
@Test public void default_methods() { assertThat("defaults to disabled", config().isDefaultMethodsEnabled(), is(false)); systemProperties.setProperty(RetrolambdaApi.DEFAULT_METHODS, "true"); assertThat("can override the default", config().isDefaultMethodsEnabled(), is(true)); }