Question

I have two classes Calculator1 and Calculator2 which are in the package called com.zzy.junit.user under the src folder. I use myeclipse to create two test classes to test them respectively. When I execute the one test class among them, how does Junit4 know which class is tested?

Class 1

package com.zzy.junit.user;

public class Calculator1 {

    private int a;
    private int b;

    public Calculator1(int a,int b)
    {
        this.a = a;
        this.b = b;
    }

    public int add()
    {
        return a+b;
    }
}

Class 2

package com.zzy.junit.user;

public class Calculator2{

    public int divide(int a,int b)
    {
        return a/b;
    }
}

And two test classes as follows:
They are both in the src folder called test

Test Class 1

package com.zzy.junit.user;

import static org.junit.Assert.*;
import static org.hamcrest.Matchers.*;  

import org.junit.Test;

public class TestCalculator1 {

    @Test
    public void testAdd() {
        Calculator1 s = new Calculator1(3,6);
        int z = s.add();
        assertThat(z,is(9));
    }

}

Test Class 2

package com.zzy.junit.user;

import static org.junit.Assert.*;
import static org.hamcrest.Matchers.*;

import org.junit.Test;

public class TestCalculator2 {

    @Test
    public void testDivide() {
        TestCalculator2 t = new TestCalculator2();
        int z = t.divide(4, 2);
        assertThat(z,is(2));
    }

}

I want to know if I execute the test class called TestCalculator2, how does Junit4 know I do want to test Calculator1 class. Is it related to the name of the test class?

Answer 1

JUnit is a framework for executing tests that can pass or fail. The fact that a single test typically focusses on a single class is a convention observed by most Java programmers. JUnit4 doesn’t know which classes are being tested, it merely executes all methods annotated with @Test.