### Question:
CaseTools { public static String ucase(String s) { return xcase(s, Character::toUpperCase); }  static String lcase(String s); static String ucase(String s); static String camel(String s); static String snake(String s);  }### Answer:
@Test @DisplayName("ucase converts properly normal not empty string that starst with a letter") void ucaseConverts() { assertEquals("Abc", ucase("abc")); }
@Test @DisplayName("ucase converts properly empty string") void ucaseConvertsZeroLengthString() { assertEquals("", ucase("")); }
@Test @DisplayName("ucase converts properly null string") void ucaseConvertsNull() { assertNull(ucase(null)); }