JUnit test for setter method

Question

    public class Room extends java.lang.Object implements java.io.Serializable {

            public String description;
            public Map<String, Room> map;
            public List<Thing> things;

            //Room
            //Parameters:
            //desc - Description for the room Note: any newlines in desc will be 
            replaced with *

            public Room(java.lang.String desc){
                this.description = desc;
            }
            //getDescription
            //A description of the room
            //Returns:
            //Description

            public java.lang.String getDescription(){
                return description;
            }
            //replaceLine
            //any new line in s will be replaced with *

            public String replaceLine(String s){
                return s.replace("\n", "*");
            }

            //setDescription
            //Change Room description Note: any newlines in s will be 
            //replaced with *
            //Parameters:
            //s - new Description

            public void setDescription(java.lang.String s){
                    this.description = replaceLine(s);
            }
}

I am trying to write a Junit test for the last method:

@Test
    public void setDescription(java.lang.String s) {
        String input = "abc\n";
        String expected = "abc";
        setDescription(input);
        assertEquals(expected, input);
    }

I know that it is not correct but I have no idea how to fix it. I am pretty new to Java and coding as a whole. Could someone please help me with this?

Answer 1

Lets assume you have created a Room instance for the test class.

...
Room room = new Room("test room");
...
@Test
public void testSetDescription() {
    assertEquals("abc", room.setDescription("abc"));
    assertEquals("abc*", room.setDescription("abc\n"));
}

You can add more such assertions based on your expectations. How setDescription handles empty string or a null input; all such use cases can be asserted in your UT.

BTW, you don't have to explicitly extend Object. Every class extends from Object implicitly either directly or indirectly through inheritance. You also don't have to use the fully qualified names of anything in java.lang package. They are implicitly imported. Also, if replaceLine should be part of the public API, you may want to add similar unit test case for that, for example public void testReplaceLine() {...}. Welcome to Java programming!

Answer 2

Here is your test:

@Test
  public void testSetDescription() {
    Room instance = new Room("test");
    instance.setDescription("abc\n");
    assertEquals("abc*", instance.getDescription());
  }

The assertEquals method is oveloaded and can be used in many ways. In this case we set in first place the expectation an on the second place what we really have (actual data) from the object. But in real life, most useful test is a test which check only single method, but in your case you call for one method but actually test other method. In real project you shouldn't test getters and setters. Only business logic, because if you'll test each method you will newer have time for main code.

Answer 3

I didn't get the problem. Could you post the error?

In the first class the replaced with * is outside the comment block, you must put // before that sentence

The Unit test aren't testing your Room class, you must do something like this:

@Test
public void testDescription(java.lang.String s) {
    String input = "abc\n";
    String expected = "abc";

    //create your Room instance 
    Room myRoom = new Room(input);//why using a constructor with description if you set the description after?
    //set the description in your Room instance
    myRoom.setDescription(input);

    //test your set-get Description against your expected result
    assertEquals(expected, myRoom.getDescription());
}