Can junit test that a method will throw an exception?

Question

Could you tell me please, is it normal practice to write a method (example: JUnit Test) that throws an Exception, for example:

class A {
    public String f(int param) throws Exception {
        if (param == 100500)
            throw new Exception();
        return "";
    }
}

private A object = new A();

@Test
public void testSomething() throws Exception {
    String expected = "";
    assertEquals(object.f(5), expected);
}

In fact, method f() won't throw an exception for that parameter(5) but nevertheless I must declare that exception.

Answer 1

Yes it is completely fine, and if it does throw the exception the test will be considered as failed.

You need to specify that the method throws an Exception even if you know that the specific case does not (this check is done by the compiler).

In this case, what you expect is object.f(5) returns an empty string. Any other outcome (non-empty string or throwing an exception) would result in a failed test case.