StringUtils { public static String upperCase(final String str) { if (str == null) { return null; } return str.toUpperCase(); }  static String upperCase(final String str); static boolean equals(final String cs1, final String cs2); static boolean isBlank(final String cs); static boolean isNotBlank(final String cs); static String replaceFirst(final String str, final String prefix);  }
@Test public void test_upperCase() { String str = "abc"; String result = StringUtils.upperCase(str); Assertions.assertEquals("ABC", result); }
@Test public void test_upperCase_null() { String result = StringUtils.upperCase(null); HyenaAssert.isNull(result, "result should be null"); }