1.Runner

上一節(jié)講到了Junit的運(yùn)行實(shí)際上是調(diào)用Runner中的run方法執(zhí)行的官撼，那么接下來總結(jié)一下Runner，首先我們看下Runner的類圖

Runner

2.Runner的構(gòu)建

讓我們回到類Request.class中的classes方法

public static Request classes(Computer computer, Class<?>... classes) {
    try {
        AllDefaultPossibilitiesBuilder builder = new AllDefaultPossibilitiesBuilder(true);
        Runner suite = computer.getSuite(builder, classes);
        return runner(suite);
    } catch (InitializationError e) {
        throw new RuntimeException(
                "Bug in saff's brain: Suite constructor, called as above, should always complete");
    }
}

由此可知第一個(gè)Runner是由computer.getSuite(builder, classes)中獲得医男，參數(shù)builder是直接new AllDefaultPossibilitiesBuilder，從名稱可以看出，這個(gè)builder是所有默認(rèn)的可能builder佑稠，看起來很牛逼的樣子，點(diǎn)進(jìn)去可以發(fā)現(xiàn)構(gòu)造方法只有一個(gè)屬性賦值旗芬，先忽略讶坯，繼續(xù)看computer.getSuite(builder, classes)

public Runner getSuite(final RunnerBuilder builder,
        Class<?>[] classes) throws InitializationError {

    return new Suite(new RunnerBuilder() {
        @Override
        public Runner runnerForClass(Class<?> testClass) throws Throwable {
            return getRunner(builder, testClass);
        }
    }, classes);
}

protected Runner getRunner(RunnerBuilder builder, Class<?> testClass) throws Throwable {
    return builder.runnerForClass(testClass);
}

由此可見這個(gè)Runner是直接new的一個(gè)Suite，進(jìn)入 Suite類看該處調(diào)用的構(gòu)造方法岗屏，

public Suite(RunnerBuilder builder, Class<?>[] classes) throws InitializationError {
    this(null, builder.runners(null, classes));
}
protected Suite(Class<?> klass, List<Runner> runners) throws InitializationError {
    super(klass);
    this.runners = Collections.unmodifiableList(runners);
}

• 可見最終是調(diào)用Suite的protected Suite(Class<?> klass, List<Runner> runners)構(gòu)造方法構(gòu)建的Suite辆琅，

• 該參數(shù)中的List<Runner> runners是由builder.runners而來漱办，而由前而的調(diào)用鏈可知，這個(gè)builder是在Computer類中getSuite的方法中婉烟，在new Suite時(shí)直接new的一個(gè)匿名的RunnerBuilder

• 該RunnerBuilder實(shí)現(xiàn)了runnerForClass方法娩井，而該方法的具體實(shí)現(xiàn)是由上文(Request類classes方法)中AllDefaultPossibilitiesBuilder來實(shí)現(xiàn)的，該處又是一個(gè)鉤子方法似袁，即當(dāng)調(diào)用這個(gè)Suite對(duì)象的runnerForClass方法時(shí)洞辣，實(shí)際調(diào)用的是AllDefaultPossibilitiesBuilder的runnerForClass。

• 讓我們回到Suite的構(gòu)建中昙衅，由剛才的構(gòu)造方法可以看出扬霜，在構(gòu)建Suite之前先調(diào)用了匿名RunnerBuilder實(shí)例中的runners，繼續(xù)看這個(gè)RunnerBuilder.runners都做了什么

    public List<Runner> runners(Class<?> parent, Class<?>[] children)
        throws InitializationError {
        //添加父class而涉，此時(shí)由Suite調(diào)用過來時(shí)為null
        addParent(parent);
        try {
            //此時(shí)的children是從開始一路傳遞下來的測(cè)試類的class
            return runners(children);
        } finally {
            //移除父class
            removeParent(parent);
        }
    }
  

繼續(xù)看該方法中調(diào)用的runners方法

 private List<Runner> runners(Class<?>[] children) {
    ArrayList<Runner> runners = new ArrayList<Runner>();
    for (Class<?> each : children) {
        //循環(huán)遍歷所有測(cè)試類的class著瓶，構(gòu)建Runner
        //由此可以發(fā)現(xiàn)每個(gè)測(cè)試類對(duì)應(yīng)一個(gè)Runner
        Runner childRunner = safeRunnerForClass(each);
        if (childRunner != null) {
            runners.add(childRunner);
        }
    }
    return runners;
}

繼續(xù)看safeRunnerForClass方法

public Runner safeRunnerForClass(Class<?> testClass) {
    try {
        return runnerForClass(testClass);
    } catch (Throwable e) {
        return new ErrorReportingRunner(testClass, e);
    }
}

• 該方法實(shí)際是調(diào)用的runnerForClass來得到的Runner，再看下方法所在類：抽象類RunnerBuilder方法中
• 還記得我們現(xiàn)在是哪個(gè)環(huán)節(jié)中嘛啼县，正是在new Suite的構(gòu)建方法中材原，所以這個(gè)地方的玄機(jī)就在于，該處的RunnerBuilder是前創(chuàng)建new Suite時(shí)創(chuàng)建的匿名RunnerBuilder季眷，而這個(gè)匿名RunnerBuilder的runnerForClass正是由Request.classes方法中new的AllDefaultPossibilitiesBuilder對(duì)象來實(shí)現(xiàn)的余蟹。
  這就是鉤子方法的妙用，也稱為模板方法
  接下來就讓我們看下AllDefaultPossibilitiesBuilder的runnerForClass
  讓我們來看下調(diào)用時(shí)序

Suite創(chuàng)建時(shí)Builder的調(diào)用

3.RunnerBuilder

首先來看上文中調(diào)用的AllDefaultPossibilitiesBuilder.runnerForClass

public Runner runnerForClass(Class<?> testClass) throws Throwable {
            //初始化RunnerBuilder列表
            //該處將Junit所有的RunnerBuilder都創(chuàng)建好放入集合
            //從該處可以以知道該類為什么叫AllDefaultPossibilitiesBuilder了

    List<RunnerBuilder> builders= Arrays.asList(
            ignoredBuilder(),  //IgnoredBuilder需要忽略測(cè)試的RunnerBuilder
            annotatedBuilder(),  //AnnotatedBuilder帶有注解的RunnerBuilder
            suiteMethodBuilder(),  //SuiteMethodBuilder
            junit3Builder(),  //JUnit3Builder（目測(cè)是為了兼容junit3）
            junit4Builder());  //JUnit4Builder

    for (RunnerBuilder each : builders) {
        Runner runner= each.safeRunnerForClass(testClass);
        if (runner != null)
            return runner;
    }
    return null;
}

• 由以上代碼可以發(fā)現(xiàn)子刮，在AllDefaultPossibilitiesBuilder中威酒，首先把所有RunnerBuilder都構(gòu)建好
• 然后循環(huán)遍歷，調(diào)用每一個(gè)builder的safeRunnerForClass方法
• 進(jìn)入該方法不難發(fā)現(xiàn)實(shí)際是調(diào)用每一個(gè)builder的runnerForClass方法挺峡，只要命中任何一個(gè)builder的構(gòu)建規(guī)則兼搏，即使用該builder創(chuàng)建Rnner，然后退出循環(huán)
• 該處應(yīng)用正是一個(gè)責(zé)任鏈模式

讓我們逐個(gè)看看各個(gè)builder的runnerForClass

1. IgnoredBuilder:

    public Runner runnerForClass(Class<?> testClass) {
        if (testClass.getAnnotation(Ignore.class) != null)
            return new IgnoredClassRunner(testClass);
        }
        return null;
    }
   

可見如果測(cè)試類中加上了@Ignore則會(huì)使用該builder

2. AnnotatedBuilder：

    public Runner runnerForClass(Class<?> testClass) throws Exception {
        //獲取測(cè)試類中用RunWith注解標(biāo)注的類
        RunWith annotation= testClass.getAnnotation(RunWith.class);
        if (annotation != null)
            return buildRunner(annotation.value(), testClass);
        return null;
     }
   
    public Runner buildRunner(Class<? extends Runner> runnerClass,
        Class<?> testClass) throws Exception {
        try {
            ////創(chuàng)建RunWith注解中聲明類的實(shí)例沙郭，并將測(cè)試類的class傳入
            return runnerClass.getConstructor(Class.class).newInstance(
                new Object[] { testClass });
        } catch (NoSuchMethodException e) {
            //先忽略異常處理
    }
   

• 由該段代碼可知佛呻，如果測(cè)試中在@RunWith注解中指定了Runner，則使用該builder病线，并使用反射創(chuàng)建指定的Runner
• 看到此吓著，相信你知道為什么我們?cè)谟肑unit寫單測(cè)的時(shí)候，單測(cè)類上面注解@RunWith的用途了

3. SuiteMethodBuilder：
   進(jìn)入suiteMethodBuilder()方法

    protected RunnerBuilder suiteMethodBuilder() {
        if (fCanUseSuiteMethod)
            return new SuiteMethodBuilder();
        return new NullBuilder();
    }
   

首先我們看到的是不是直接new SuiteMethodBuilder送挑，而是首先看fCanUseSuiteMethod屬性是否為true绑莺，還記得該屬性是什么時(shí)候賦值的嘛？返回去看下Request.classes方法

public static Request classes(Computer computer, Class<?>... classes) {
    try {
        AllDefaultPossibilitiesBuilder builder = new AllDefaultPossibilitiesBuilder(true);
        Runner suite = computer.getSuite(builder, classes);
        return runner(suite);
    } catch (InitializationError e) {
        throw new RuntimeException(
                "Bug in saff's brain: Suite constructor, called as above, should always complete");
    }
}

正是new AllDefaultPossibilitiesBuilder(true); 中的true
也就是說惕耕，測(cè)試類中如果沒有ignored和annotated纺裁，首先使用的RunnerBuilder實(shí)際是SuiteMethodBuilder，并執(zhí)行該builder的runnerForClass方法，進(jìn)入一探究竟

public Runner runnerForClass(Class<?> each) throws Throwable {
    //判斷測(cè)試的class中是否有suite方法
    if (hasSuiteMethod(each))
        //創(chuàng)建suiteMethod欺缘，該類繼承自JUnit38ClassRunner
        return new SuiteMethod(each);
    return null;
}

public boolean hasSuiteMethod(Class<?> testClass) {
    try {
        testClass.getMethod("suite");
    } catch (NoSuchMethodException e) {
        return false;
    }
    return true;
}

• 根據(jù)此段代碼可以發(fā)現(xiàn)栋豫，如果測(cè)試類中沒有suite方法的話返回的是null
• 此時(shí)在 AllDefaultPossibilitiesBuilder.runnerForClass中會(huì)繼續(xù)循環(huán)尋找下一下builder

4. JUnit3Builder：如果測(cè)試類使用的是Junit3的測(cè)試方式，則使用該builder谚殊，?該builder不再細(xì)看

5. JUnit4Builder：該builder很簡(jiǎn)單丧鸯，直接new BlockJUnit4ClassRunner

    public Runner runnerForClass(Class<?> testClass) throws Throwable {
        return new BlockJUnit4ClassRunner(testClass);
    }
   

• 從以上AllDefaultPossibilitiesBuilder.runnerForClass方法的執(zhí)行看來，Junit4默認(rèn)使用的builder是BlockJUnit4ClassRunner

讓我們?cè)倩氐轿覀兊闹骶€new Suite中嫩絮，

public Suite(RunnerBuilder builder, Class<?>[] classes) throws InitializationError {
    this(null, builder.runners(null, classes));
}
protected Suite(Class<?> klass, List<Runner> runners) throws InitializationError {
    super(klass);
    //Collections.unmodifiableList將傳入的List變得不可修改
    this.runners = Collections.unmodifiableList(runners);
}

• 由以上流程可知丛肢，在創(chuàng)建Suite這個(gè)Runner時(shí)，首先把所有測(cè)試類對(duì)應(yīng)的具體Runner通過對(duì)應(yīng)的RunnerBuilder構(gòu)建好剿干，放入Suite的List<Runner> runners屬性中蜂怎，至此Suite構(gòu)建完成(構(gòu)造方法中的super(klass)后續(xù)再看)

總之，JunitCore中使用的Runner是直接new的Suite置尔，而這個(gè)Suite中屬性List<Runner> runners杠步，默認(rèn)情況下，這些runner都是BlockJUnit4ClassRunner
至此Runner的構(gòu)建完成撰洗，讓我來接下來看下整個(gè)Runner構(gòu)建的時(shí)序圖

4.Runner構(gòu)建時(shí)序圖

Runner構(gòu)建時(shí)序圖