FileHeaderCheck implements EslintBasedCheck { @Override public List<Object> configurations() { return Collections.singletonList(new Config(headerFormat, isRegularExpression)); }  @Override List<Object> configurations(); @Override String eslintKey(); @RuleProperty(
    key = "headerFormat",
    description = "Expected copyright and license header",
    defaultValue = DEFAULT_HEADER_FORMAT,
    type = "TEXT")
  public String headerFormat; @RuleProperty(
    key = "isRegularExpression",
    description = "Whether the headerFormat is a regular expression",
    defaultValue = "false")
  public boolean isRegularExpression; }
@Test public void config() { final FileHeaderCheck check = new FileHeaderCheck(); String configAsString = new Gson().toJson(check.configurations()); assertThat(configAsString).isEqualTo("[{\"headerFormat\":\"\",\"isRegularExpression\":false}]"); check.headerFormat = " check.isRegularExpression = true; configAsString = new Gson().toJson(check.configurations()); assertThat(configAsString).isEqualTo("[{\"headerFormat\":\" }