### Question:
Keymaker { public Keymaker(final String namespace) { this.namespace = checkNotNull(namespace, "Namespace cannot be null"); } Keymaker(final String namespace); Keymaker build(final String... namespaces); @Override String toString();  }### Answer:
@Test public void testKeymaker() { checkKeymaker(""); checkKeymaker(":"); checkKeymaker("test"); checkKeymaker(":test:"); checkKeymaker("test::"); checkKeymaker("::test"); checkKeymaker("test:test2"); }