### Question:
OrganizationFactory { public DirectoryClient makeDirectoryClient(String directoryId) { if (directoryId == null) throw new IllegalArgumentException("Argument directoryId cannot be null"); UUID directoryUUID = UUID.fromString(directoryId); return new BasicDirectoryClient(directoryUUID, transport); } OrganizationFactory(Transport transport, UUID organizationId); DirectoryClient makeDirectoryClient(String directoryId); ServiceClient makeServiceClient(String serviceId); OrganizationClient makeOrganizationClient();  }### Answer:
@Test(expected = IllegalArgumentException.class) public void testMakeDirectoryClientWithNullThrowsIllegalArgument() throws Exception { organizationFactory.makeDirectoryClient(null); }
@Test(expected = IllegalArgumentException.class) public void testMakeDirectoryClientWithInvalidUUIDThrowsIllegalArgument() throws Exception { organizationFactory.makeDirectoryClient("Not A UUID"); }
@Test public void testMakeDirectoryClientWithValidUUIDReturnsClient() throws Exception { assertThat( organizationFactory.makeDirectoryClient("49af9c38-31b3-11e7-93ae-92361f002671"), instanceOf(DirectoryClient.class) ); }