使用JUnit进行单元测试

Profile：

JUnit is a simple framework to write repeatable tests. It is an instance of the xUnit architecture for unit testing frameworks.

由于使用的eclipse版本自带了JUnit所以不用下载即可使用，如果要下载可在官网junit.org下载jar包。

下面是一个简单的计算器程序：

先编写计算器接口ICalculator.java用于描述功能：

package Calculate;

public interface ICalculator {
    
    public double add(double arg1, double arg2);
    
    public double subtract(double arg1, double arg2);
    
    public double division(double arg1, double arg2);
    
    public double multiply(double arg1, double arg2);
    
}

在编写接口实现类Calculator.java：

package Calculate;

public class Calculator implements ICalculator {

    @Override
    public double add(double arg1, double arg2) {
        
        return arg1 + arg2;
    }

    @Override
    public double subtract(double arg1, double arg2) {
        
        return arg1 - arg2;
    }

    @Override
    public double division(double arg1, double arg2) {
        
        return arg1/arg2;
    }

    @Override
    public double multiply(double arg1, double arg2) {
        
        return arg1*arg2;
    }

}

点击项目右键新建junit test case创建测试类CalculateTest.java，选择对应的包和要测试的类：

package Calculate;

import static org.junit.Assert.*;

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

public class CalculateTest {

    private ICalculator _calculator = new Calculator();
    
    @Before
    public void setUp() throws Exception {
    }

    @Test
    public void testAdd() {
        assertEquals(5, _calculator.add(2, 3), 0);
        assertEquals(5, _calculator.add(3, 2), 0);
        assertEquals(2, _calculator.add(2, 0), 0);
        assertEquals(2, _calculator.add(0, 2), 0);
        assertEquals(0, _calculator.add(0, 0), 0);
        assertNotEquals(0, _calculator.add(0, 2));
    }

    @Test
    public void testSubtract() {
        assertEquals(5, _calculator.subtract(10, 5), 0);
        assertEquals(5, _calculator.subtract(5, 0), 0);
        assertEquals(-5, _calculator.subtract(0, 5), 0);
        assertEquals(0, _calculator.subtract(0, 0), 0);
    }

    @Test
    public void testDivision() {
        assertEquals(0, _calculator.division(5, 0), 0);
        assertEquals(0, _calculator.division(0, 5), 0);
        assertEquals(2.5, _calculator.division(5, 2), 0);
        assertEquals(5, _calculator.division(10, 2), 0);
    }

    @Test
    public void testMultiply() {
        assertEquals(0, _calculator.multiply(2, 0), 0);
        assertEquals(4, _calculator.multiply(2, 2), 0);
        assertEquals(0, _calculator.multiply(0, 0), 0);
        assertNotEquals(2, _calculator.multiply(2, 0));
        assertNotEquals(0, _calculator.multiply(5.0, 0));
    }

}

写完测试用例后，右键CalculateTest.java 点击Run as->JUnit Test即可，下面是结果截图：

从测试结果可以看到，add, subtract, multipy是通过测试的，division没通过。

代码github地址：https://github.com/GreenLim/JUnitTest