@Test 
    // test getNumber with a valid input. 
    public void getNumberValidInput() { 
        // When the getNumber calls Scanner.nextLine() return "496" via  
        // the mocked Scanner. 
        // declare a mock Scanner object. 
        Scanner mockScanner = mock(Scanner.class); 
        when (mockScanner.nextLine()).thenReturn("496"); 
        int val = PrimeOrPerfect.getNumber(mockScanner); 
        assertEquals(496, val); 
    } 
    

When I run my code as a maven install I get an error on the line Scanner mockScanner = mock(Scanner.class);. I don’t understand why and I can’t contact my professor.

I expect the test to run but I keep getting an illegalstate error.