Java Junit 单元测试

先编写一个类

public class Calculator {
	
	public int result = 0;
	
	public int add(int operand1, int operand2) {
		result = operand1 + operand2;
		return result;
	}
	
	public int subtract(int operand1, int operand2) {
		result = operand1 - operand2;
		return result;
	}
	
	public int multiple(int operand1, int operand2) {
		result = operand1 * operand2;
		for(;;) {}
	}
	
	public int divide(int operand1, int operand2) {
		result = 1/0;
		return result;
	}
	
	public int getResult() {
		return this.result;
	}
}

然后在类名上右键新建Junit 测试 Case:

之后编写测试代码：

import static org.junit.Assert.*;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.fail;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Ignore;
import org.junit.Test;

public class CalculatorTest2 {
	
	private static Calculator cal = new Calculator();

	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
		System.out.println("Beforeclass");
	}

	@AfterClass
	public static void tearDownAfterClass() throws Exception {
		System.out.println("after class");
	}

	@Before
	public void setUp() throws Exception {
		System.out.println("开始");
	}

	@After
	public void tearDown() throws Exception {
		System.out.println("结束");
	}


	@Test
	public void testAdd() {
		cal.add(2, 2);
		assertEquals(4, cal.getResult());
		System.out.println("测试加");
	}
	
	@Test
	public void testSub() {
		cal.subtract(4, 2);
		assertEquals(3,cal.getResult());
		System.out.println("测试减");
	}
	
	@Ignore
	public void testMul() {
		fail("not yet implemented");
	}
	
	@Test(timeout = 2000)
	public void testDivide() {
		for(;;);
	}
	
	@Test(expected = ArithmeticException.class)
	public void testDiv() {
		cal.divide(4, 0);
	}

}

测试结果：

注意：
Junit4 和 Junit5 的语法不一样，不要混用。
否则会报the attribute timeout is undefined for the annotation type Test类似的错。