Writing Unit test for mutator

Question

Writing unit tests for mutators are only slightly different from that of constructors. The steps used are:

1. Create an object with initial values.
2. Call the mutator method that will change the object
3. Use assertEquals and call the accessor method for each of the instance variables or calculations to make sure they contain the expected (new) values.

Given the following constructor for a fictitious Time class:

public Time(int hours, int minutes, int seconds);

Write the unit test statements to test each method as indicated below. Note that the first part, creating an object to test, has been done for you in each method.

a.

public void setHours(int hours);

public int getHours();

@Test

public void testSetHours() {

Time time = new Time(4, 14, 43);

Answer 1

I believe the following code would solve this problem. After the time object has already been created, the first assertEquals() will check to make sure that initial hours of 4 that was given to the time object is correct. If the first assertEquals() statement passes, then you know that the getHours() function and the constructor are working correctly. After that, you should call the mutator setHours(int hours) on the time object with some integer inside. If that mutator works correctly, then the hours of the time object should be updated correctly. The second assertEquals() will check to make sure that the hours were updated.

 

@Test

public void testSetHours() {

  Time time = new Time(4, 14, 43);

 

assertEquals(time.getHours(), 4);

time.setHours(10);

assertEquals(time.getHours(), 10);

}