RichMenuImageUploadCommand implements CliCommand { @VisibleForTesting static String resolveContentTypeForFileName(final String fileName) { return FILE_NAME_MAP.getContentTypeFor(fileName); }  @Override void execute();  }
@Test public void resolveContentTypeForFileNameTest() { final Function<String, String> target = RichMenuImageUploadCommand::resolveContentTypeForFileName; assertThat(target.apply("image.PNG")).isEqualTo("image/png"); assertThat(target.apply("image.png")).isEqualTo("image/png"); assertThat(target.apply("image.jpg")).isEqualTo("image/jpeg"); assertThat(target.apply("image.jpeg")).isEqualTo("image/jpeg"); }