Jmockit 入门

在单元测试中，经常需要进行一些mock操作。现在已经有了一些比较不错的框架在做这些事情，比如：EasyMck，他在大多数情况下运行良好，但是对于某些结构的设计却显得无能为力。

EasyMock等众多的mock框架仅能mock一些public，non static or final的方法，在大多数情况下这并没有什么问题，他可以处理大多数的问题，但是当测试的代码包含了一些静态方法，可能就让问题变得难以解决，有一种选 择即是重构他（过多的静态方法可能预示着这并不是一个很好的设计），但是当你使用外部引用库所提供的方法，问题又该如何解决呢？

JMockit是一个能帮我们解决以上问题的轻量级框架，他允许你动态的改变已有的方法，这主要基于java 1.5的Instrumentation框架，这样便可以使得JMockit能够适应几乎所有的设计。他允许你重定义private,static and final方法，甚至是no-arg constructors都能够并轻易的重定义。

在实际的项目中有些方法可以重定义而有些不行，为了更好的说明如何对方法进行重定义，下面有一个简单的类和对应测试代码的demo，他尽可能考虑到了几乎所有的情况，供大家方便的学习。（理解不透的地方，希望大家指正）

package jmockit;

public class ClassToMock {
	private String memberToSet = "";
    private static String staticMember;
    
    static {
        staticMember = "Static initialized";
    }
    
    public ClassToMock() {
        this.memberToSet = "Member set by original constructor";
    }
    public ClassToMock(String value){
    	this.memberToSet = value;
    }
    public String publicMethod() {
            return "Original public method";
    }
    protected String protectedMethod() {
            return "Original protected method";
    }
    String defaultMethod() {
            return "Original default method";
    }
    public String methodThatUsesPrivateMethod() {
            return privateMethod();
    }
    private String privateMethod() {
            return "Original private method";
    }
    public String getMemberToSet() {
            return memberToSet;
    }
    public String getStaticMember() {
            return staticMember;
    }
}

 

package jmockit;

import static org.junit.Assert.assertEquals;
import mockit.Mockit;

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

public class ClassToMockTest {

private ClassToMock mockedClass;

public static class Replacement {

static {
}

public Replacement() {
}

public Replacement(String test) {
}

public String publicMethod() {
return "Replaced public method";
}

public String protectedMethod() {
return "Replaced protected method";
}

public String defaultMethod() {
return "Replaced default method";
}

public String privateMethod() {
return "Replaced private method";
}
}

@Before
public void setUp() throws Exception {
Mockit.redefineMethods(ClassToMock.class, Replacement.class);
mockedClass = new ClassToMock("test");
}

protected void tearDown() throws Exception {
Mockit.restoreAllOriginalDefinitions();
}

/**
* Public methods can be replaced
*/
@Test
public void testReplacePublic() {
assertEquals("Replaced public method", mockedClass.publicMethod());
}

/**
* Protected methods can be replaced.
* The replacement method should be declared public however
*/
@Test
public void testReplaceProtected() {
assertEquals("Replaced protected method", mockedClass.protectedMethod());
}

/**
* Package accessable methods can be replaced
* The replacement method should be declared public however
*/
@Test
public void testReplaceDefault() {
assertEquals("Replaced default method", mockedClass.defaultMethod());
}

/**
* Private methods can be replaced
* The replacement method should be declared public however
*/
@Test
public void testReplacePrivate() {
assertEquals("Replaced private method", mockedClass
.methodThatUsesPrivateMethod());
}

/**
* Non-default constructors can be replaced
* Your mock definition must have a default constructor however
*/
@Test
public void testReplaceConstructor() {
assertEquals(null, mockedClass.getMemberToSet());
}

/**
* Default constructors <b>can't</b> be replaced
*/
@Test
public void testReplaceDefaultConstructor() {
mockedClass = new ClassToMock();
assertEquals("Member set by original constructor", mockedClass
.getMemberToSet());
}
/**
* Static initializers <b>can't</b> be replaced
*/
@Test
public void testReplaceStaticBlock() {
assertEquals("Static initialized", mockedClass.getStaticMember());
}
}

 注意要导包。

 官方文档：https://jmockit.dev.java.net/tutorial.html