Junit4学习笔记（一）-优快云博客

本文详细介绍了一个简单的JUnit单元测试案例，包括环境搭建、测试类编写、运行测试及解析测试结果等步骤。通过修改被测类的方法，展示了测试失败的情况及其原因。

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1.安装JDK；

2.新建文件夹命名为junit-example，下载junit-4.12.jar 和 hamcrest-core-1.3.jar 放入junit-example文件夹中；

3.新建Calculator.java. 放入junit-example文件夹中，内容如下：

1 public class Calculator {
2   public int evaluate(String expression) {
3     int sum = 0;
4     for (String summand: expression.split("\\+"))
5       sum += Integer.valueOf(summand);
6     return sum;
7   }
8 }

然后在cmd中执行命令：javac Calculator.java

4.新建CalculatorTest.java. 放入junit-example文件夹中，内容如下：

 1 import static org.junit.Assert.assertEquals;
 2 import org.junit.Test;
 3 public class CalculatorTest {
 4   @Test
 5   public void evaluatesExpression() {
 6     Calculator calculator = new Calculator();
 7     int sum = calculator.evaluate("1+2+3");
 8     assertEquals(6, sum);
 9   }
10 }

然后在cmd中执行命令：javac -cp .;junit-4.12.jar CalculatorTest.java

5.在cmd中执行命令：java -cp .;junit-4.12.jar;hamcrest-core-1.3.jar org.junit.runner.JUnitCore CalculatorTest

输出结果为：

JUnit version 4.12
.
Time: 0.004

OK (1 test)

6.将Calculator.java中的sum += Integer.valueOf(summand);替换为sum -= Integer.valueOf(summand);

然后在cmd中重新执行命令：javac Calculator.java 及 java -cp .;junit-4.12.jar;hamcrest-core-1.3.jar org.junit.runner.JUnitCore CalculatorTest

输出结果为：

JUnit version 4.12
.E
Time: 0.007
There was 1 failure:
1) evaluatesExpression(CalculatorTest)
java.lang.AssertionError: expected: but was:
        at org.junit.Assert.fail(Assert.java:88)
        at org.junit.Assert.failNotEquals(Assert.java:834)
        at org.junit.Assert.assertEquals(Assert.java:645)
        at org.junit.Assert.assertEquals(Assert.java:631)
        at CalculatorTest.evaluatesExpression(CalculatorTest.java:9)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
        at org.junit.runners.Suite.runChild(Suite.java:128)
        at org.junit.runners.Suite.runChild(Suite.java:27)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
        at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
        at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
        at org.junit.runner.JUnitCore.runMain(JUnitCore.java:77)
        at org.junit.runner.JUnitCore.main(JUnitCore.java:36)

FAILURES!!!
Tests run: 1,  Failures: 1

7.cmd中命令执行全过程如下图：