A quick refactoring using TestNG’s expectedExceptions

I recently crossed a TestNG-test which looked like this:

public void noResultsTest() {
	// test
	String query = " ";
	Exception exception = null;
	List foos = null;
	try {
		foos = barService.search(query);
	} catch (SystemError e) {
		// input was wrong
		exception = e;

	// assert
	Assert.assertNotNull(exception, "There was an exception");

Obviously this test should check that barService#search throws an Exception in case the input is a blank.

But there are a few things to mention:

  • TestNG is capable of checking if an expected exception was thrown in a test. Simply use @Test(expectedExceptions={..}).
  • The check that Assert.assertNull(foos) holds true is useless. Either no exception was thrown and Assert.assertNotNull(exception, "There was an exception") will fail or an exception was thrown and foos will not be assigned with any value.

So the test could be rewritten like this:

@Test(expectedExceptions={ SystemError.class })
public void keineBerufeTest2() throws SystemError {
	foos = barService.search(" ");

Rolf Engelhard


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