Junit-如何测试参数的无效用法

Question

I am supposed to write a Junit test for the invalid usage of correct parameters. I am a bit confused by this concept. Can someone please help to explain what is this scenario, and how to do this with an example?

I am testing a method that take a customer and a type of service as parameters. and I've tried the assertFalse method below, and tried to pass two customers to

assertFalse("Registration fails for add two services to one customer", cs.addPeople("Jack", "Jill","Cleaning"));

I realized that this is not the correct way as the add.People() method only takes one person as a parameter. In this case how can we test invalid usage? Many thanks!

Answer 1

By test invalid usage of parameters, I guess you mean write scenarios with invalid parameters. For example. Say that you have a method:

public Integer toInteger(String input){
   //conversion logic
}

Now, you would want to know how your method behaves on different scenarios. One scenario would be passing invalid parameter such as null , and see how your method behaves.

@Test
public void testToIntegerForNullParam(){
   myClass.toInteger(null);
}

This method will not pass if you didn't handle null checking, and you will have to refactor to pass this test.

public Integer toInteger(String input){
   if(input == null){
      throw new IllegalArgumentException("Argument was null!"); 
    }
    //conversion logic
}

Then in your test, you can test if this indeed throws exception when argument is null. You can use expected = IllegalArgumentException.class

@Test(expected = IllegalArgumentException.class)
public void testToIntegerForNullParam(){
    myClass.toInteger(null);
}

You can continue adding more scenarios such as string not being numeric etc.