### Question:
Utils { public static String namespace(String namespace, String name) { assertNotNull(namespace, "namespace may not be null"); assertNotNull(name, "name may not be null"); assertTrue(namespace.indexOf(':') == -1, "namespace may not contain ':'"); return namespace + ':' + name; } private  Utils(); static String getNamespace(String name); static boolean isNamespaced(String name); static String namespace(String namespace, String name); static void assertNotNull(Object argument); static void assertNotNull(Object argument, Object message); static void assertNotEmpty(String value); static void assertNotEmpty(String value, Object message); static void assertNotEmpty(Map<?,?> map); static void assertNotEmpty(Map<?,?> map,  Object message); static void assertNotEmpty(Collection<?> collection); static void assertNotEmpty(Collection<?> collection,  Object message); static void assertTrue(boolean expression); static void assertTrue(boolean expression, Object message); static void assertFalse(boolean expression); static void assertFalse(boolean expression, Object message); static Map<K, V> unmodifiableCopy(Map<K, V> source); static final String serializeType(Type type); static final Type deserializeType(String type); static String b64Encode(byte[] binary); static byte [] b64Decode(CharSequence encoded); static final byte[] hash(String value); static final byte[] hash(InputStream is); static final String shortHash(InputStream is); @Deprecated static byte[] aesEncrypt(String secretStr, byte[] decrypted); @Deprecated static byte[] aesDecrypt(String secretStr, byte[] encrypted); @Deprecated static String aesEncrypt(String secretStr, String decrypted); @Deprecated static String aesDecrypt(String secretStr, String encrypted); static boolean setIf(String key, Object value, Map<String,Object> map); static Map<String, String> coerceToStringMap(Map<String, ?> value); static String coerceToString(Object value); static String randomTokenString(int length); static final Charset UTF_8; static final Object [] EMPTY_ARRAY; static final byte [] EMPTY_BYTE_ARRAY; }### Answer:
@Test public void testNamespace() throws Exception { try { Utils.namespace(null, null); fail("Created a null namespace"); } catch(IllegalArgumentException e) { } try { Utils.namespace("namespace", null); fail("Created a null namespace"); } catch(IllegalArgumentException e) { } try { Utils.namespace(null, "name"); fail("Created a null namespace"); } catch(IllegalArgumentException e) { } assertEquals("a:b", Utils.namespace("a", "b")); assertEquals("a:b:c", Utils.namespace("a", "b:c")); try { Utils.namespace("a:b", "c"); fail("Allowed invalid namespace"); } catch(IllegalArgumentException e) { } }