### Question:
StringSimpleFieldActions implements AtlasFieldAction { @AtlasActionProcessor public static Character uppercaseChar(UppercaseChar action, Character input) { if (input == null) { return null; } return String.valueOf(input).toUpperCase().charAt(0); }  @AtlasActionProcessor static String capitalize(Capitalize action, String input); @AtlasActionProcessor static String fileExtension(FileExtension action, String input); @AtlasActionProcessor static String lowercase(Lowercase action, String input); @AtlasActionProcessor static Character lowercaseChar(LowercaseChar action, Character input); @AtlasActionProcessor static String normalize(Normalize action, String input); @AtlasActionProcessor static String removeFileExtension(RemoveFileExtension action, String input); @AtlasActionProcessor static String separateByDash(SeparateByDash action, String input); @AtlasActionProcessor static String separateByUnderscore(SeparateByUnderscore action, String input); @AtlasActionProcessor static String trim(Trim action, String input); @AtlasActionProcessor static String trimLeft(TrimLeft action, String input); @AtlasActionProcessor static String trimRight(TrimRight action, String input); @AtlasActionProcessor static String uppercase(Uppercase action, String input); @AtlasActionProcessor static Character uppercaseChar(UppercaseChar action, Character input); static final String STRING_SEPARATOR_REGEX; static final Pattern STRING_SEPARATOR_PATTERN; }### Answer:
@Test public void testUpperCaseChar() { assertNull(StringSimpleFieldActions.uppercaseChar(new UppercaseChar(), null)); assertEquals('\0', StringSimpleFieldActions.uppercaseChar(new UppercaseChar(), '\0').charValue()); assertEquals('F', StringSimpleFieldActions.uppercaseChar(new UppercaseChar(), 'f').charValue()); assertEquals('F', StringSimpleFieldActions.uppercaseChar(new UppercaseChar(), 'F').charValue()); }