Example

Go to the working directory that contains "Rectangle.java" (or create a new working directory and copy "Rectangle.java" into it)
Create new file named "RectangleTests.java" in the working directory
Type or copy the code shown here into the new file

The Rectangle code can be found in this previous example...

public class RectangleTests {

	public void testSetSmall() {

	}

	public void testSetLarge() {

	}

	//=======================================

	public static void main(String[] args) {
		RectangleTests test = new RectangleTests();
		test.testSetSmall();
		test.testSetLarge();
	}

}

Construct Rectangle and assign to variable rec
Send message setSmall to var rec
Show expected width
Show actual width by sending message getWidth to var rec

We send the message "getHeight" similarly

	/**
	 * Test that the method setSmall sets the Rectangle
	 * to the expected width and height of 5 and 1.
	*/
	public void testSetSmall()  {

		Rectangle rec;

		1rec = new Rectangle();

		2rec.setSmall();

		System.out.println("-- testSetSmall --");
		System.out.println("3Expected Width: " + 5);
		System.out.println("Expected Height: " + 1);
		System.out.println("Actual Width: " + 4rec.getWidth());
		System.out.println("Actual Height: " + rec.getHeight());
	}

Test Output

The test passes if the expected and actual values match.

If they don't pass, that just means we conduct a bug hunt (i.e., finding and fixing the program bug).

-- testSetSmall --
Expected Width: 5
Expected Height: 1
Actual Width: 5
Actual Height: 1

Construct Rectangle and assign to variable rec
Send message setLarge to var rec
Show expected width
Show actual width by sending message getWidth to var rec

	/**
	 * Test that the method setSmall sets the Rectangle
	 * to the expected width and height of 100 and 50.
	*/
	public void testSetLarge()  {

		Rectangle rec;

		1rec = new Rectangle();

		2rec.setLarge();

		System.out.println("-- testSetLarge --");
		System.out.println("3Expected Width: " + 100);
		System.out.println("Expected Height: " + 50);
		System.out.println("Width: " + 4rec.getWidth());
		System.out.println("Height: " + rec.getHeight());
	}

Test Output

The test passes if the expected and actual values match.

-- testSetLarge --
Expected Width: 100
Expected Height: 50
Width: 100
Height: 50

The final test code is shown here.

It can also be downloaded

public class RectangleTests {

	/** Test that the method setSmall sets the Rectangle
	to the expected width and height of 5 and 1.*/
	public void testSetSmall() {

		Rectangle rec;

		rec = new Rectangle();

		rec.setSmall();

		System.out.println("-- testSetSmall --");
		System.out.println("Expected Width: " + 5);
		System.out.println("Expected Height: " + 1);
		System.out.println("Actual Width: " + rec.getWidth());
		System.out.println("Actual Height: " + rec.getHeight());
	}

	/** Test that the method setSmall sets the Rectangle
	to the expected width and height of 100 and 50.*/
	public void testSetLarge() {

		Rectangle rec;

		rec = new Rectangle();

		rec.setLarge();

		System.out.println("-- testSetLarge --");
		System.out.println("Expected Width: " + 100);
		System.out.println("Expected Height: " + 50);
		System.out.println("Width: " + rec.getWidth());
		System.out.println("Height: " + rec.getHeight());
	}

	//=======================================

	public static void main(String[] args) {
		RectangleTests test = new RectangleTests();
		test.testSetSmall();
		test.testSetLarge();
	}

}