[JAVA] How to run JUnit in Eclipse

What is JUnit

• Perform a tool (framework) that can perform unit tests in Java programs
• Test automation is possible
• Since manual work is reduced, it is effective in reducing test man-hours and preventing human error.

Prerequisites

• Eclipse is installed
• You have created a project, package, or program file with the following structure.

ProjectA  ----  src
                 |
                 ------ xx.yy.zzz(package)
                            |
                            ------- Door.java (Tested class)

Configuration

Create a class "DoorTest.java" for testing Door.java (test target class) under package xx.yy.zzz.

• Right-click the project in Eclipse-click [New]-[Other]

• Select "Java"-"JUnit"-"Junit Test Case" and click Next

• Set the required value referring to the figure below.

• The template of "DoorTest.java" is created.

DoorTest.java

package xx.yy.zzz;  //Make it the same package as the class under test

import static org.junit.Assert.*;

import org.junit.Test;

public class DoorTest {

	@Test
	public void test() {
		fail("Not yet implemented");
	}

}

• Let's try it. Right-click DoorTest.java and select Run-Configure Run

• Set the required value referring to the figure below. Don't forget to use "JUnit 4" as the test runner!

• Execution result. The result is always "fail" because the fail method is called.

Write a test program

Tested class

Door.java

package xx.yy.zzz;  //Make it the same package as the test class

public class Door {
	private boolean isOpen = false;

	public void open(String str) {
		if (str.equals("open Sesame!")) {
			isOpen = true;
		} else {
                        isOpen = false;
			System.out.println("wrong.");
		}
	}

	public void close() {
		isOpen = false;
	}

	// getter
	public boolean isOpen() {
		return isOpen;
	}

}

Test content

• test1. If you specify anything other than "Open sesame!" In the open method, the door will not open (the return value of the isOpen method is false). Also, the standard output is "No."
• test2. If you specify "Open sesame!" In the open method, the door will open (the return value of the isOpen method is true).
• test3. The door is closed by the close method (the return value of the isOpen method is false).

Test class

Door.java

package xx.yy.zzz;  //Make it the same package as the class under test

import static org.junit.Assert.*;

import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class DoorTest {

	Door door;
    private ByteArrayOutputStream baos;

	//Preprocessing
	@Before
	public void setUp() {
		door = new Door();

        baos = new ByteArrayOutputStream();
        System.setOut(
            new PrintStream(
                new BufferedOutputStream(baos)
            )
        );
	}


	// 「@"Test" is an annotation for JUnit to recognize as a test method.
	//Create with public void
	@Test
	public void test1() {
		door.open("Please open the door");

		//Standard output
		System.out.flush();
		String expected = "wrong.\r\n";
        String actual = baos.toString();

        //Confirmation with expected value
		assertEquals(false, door.isOpen());
        assertEquals(expected, actual);
	}

	@Test
	public void test2() {
		door.open("open Sesame!");
		assertEquals(true, door.isOpen());
	}

	@Test
	public void test3() {
		door.close();
		assertEquals(false, door.isOpen());
	}

	//Post-processing
	@After
	public void fin() {
		// DO Nothing
	}

}

[Supplement]

• System.setOut method: Reassign the "standard" output stream. The argument is the PrintStream class.
• PrintStream class: Used to create a new output stream.
• BufferedOutputStream class: Streams the data in the buffer.
• ByteArrayOutputStream class: Implements an output stream where data is written to a byte array.