@Test
public void getFunctionClassShouldReturnTheFirstFunction() {

	final Class<? extends Function> stubClass = new OperatorWithTwoFunctions().getFunctionClass();
	assertEquals(OperatorWithTwoFunctions.class, stubClass.getDeclaringClass());
	assertTrue(Arrays.asList(OperatorWithTwoFunctions.Implementation1.class,
		OperatorWithTwoFunctions.Implementation2.class).contains(stubClass));
}