文|碼術張

本文旨在說明Junit4源代碼的設計思想。
說明方式上，使用的是自己的一個創(chuàng)新的想法：
用一個ut來說明嫡丙。

代碼如下;

package test;

import org.junit.Test;

public class IpTest {

    @Test
    public void should_True() throws Exception{
        MyNotifier notifier = new MyNotifier();
        MyResult result = new MyResult();
        notifier.addListener(result.createListener());
        notifier.addListener(new Detail());
        MyDescription description = MyDescription.createMyDescriptionn("IpTest", "");

        notifier.fireTestRunStarted(description);

            MyDescription descriptionForA = MyDescription.createMyDescriptionn("IpTest", "methodA");

            notifier.fireTestStarted(descriptionForA);
            System.out.println("Hi..., I am method A");
            notifier.fireTestFinished(descriptionForA);

            MyDescription descriptionForB = MyDescription.createMyDescriptionn("IpTest", "methodB");
            notifier.fireTestStarted(descriptionForB);
            System.out.println("Hi..., I am method B");
            notifier.fireTestFinished(descriptionForB);

        notifier.fireTestRunFinished(result);

    }

}

類圖:

類圖

交互圖：

交互圖

在class IpTest中棺榔，有一個should_True方法。
這個方法的實現(xiàn)败砂，即演示了Junit4的實現(xiàn)原理。
MyNotifier龄毡、MyResult吠卷、MyDescription，
對就Junit源碼中類Notifier沦零、Result祭隔、Description。

程序運行時，首先發(fā)布一個事件fireTestRunStarted疾渴；
運行結(jié)束時千贯，發(fā)布一個一個事件fireTestRunFinished。

類的每一個方法運行時搞坝，首先發(fā)布一個事件fireTestStarted搔谴；
類的每一個方法結(jié)束時，會發(fā)現(xiàn)一個事件fireTestFinished桩撮。

Listener收到事件后敦第，會做一些操作。
這些操作的結(jié)果會在程序結(jié)時店量，打印出來：

運行結(jié)果

在Junit源代碼中芜果，每個方法會有一個用職責鏈模式構(gòu)建一個Statement類的對象。
一個方法的執(zhí)行融师，即是依次執(zhí)行這個鏈表上的語句右钾。
這點沒在本文中體現(xiàn)。

本文所用的其他代碼如下：

package test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class MyNotifier {
    private final List<MyRunListener> fListeners =
    Collections.synchronizedList(new ArrayList<MyRunListener>());

    public void addListener(MyRunListener listener) {
        fListeners.add(listener);
    }

    public void fireTestRunStarted(final MyDescription description) throws Exception {
        for (MyRunListener each : fListeners) {
                each.testRunStarted(description);
        }

    }

    public void fireTestRunFinished(final MyResult result) throws Exception{
        for (MyRunListener each : fListeners) {
                each.testRunFinished(result);
        }

    }

    public void fireTestStarted(final MyDescription description) throws Exception{
        for (MyRunListener each : fListeners) {
                each.testStarted(description);
        }       

    }

    public void fireTestFinished(final MyDescription description)   throws Exception{
        for (MyRunListener each : fListeners) {
                each.testFinished(description);
        }   

    }
}

package test;

import java.util.concurrent.atomic.AtomicInteger;

public class MyResult {

    private AtomicInteger fCount = new AtomicInteger();
    private long fRunTime = 0;
    private long fStartTime;

    public int getRunCount() {
        return fCount.get();
    }

    public long getRunTime() {
        return fRunTime;
    }   

    private class Listener extends MyRunListener {
        @Override
        public void testRunStarted(MyDescription description) throws Exception {
            fStartTime = System.currentTimeMillis();
        }

        @Override
        public void testRunFinished(MyResult result) throws Exception {
            long endTime = System.currentTimeMillis();
            fRunTime += endTime - fStartTime;
        }

        @Override
        public void testFinished(MyDescription description) throws Exception {
            fCount.getAndIncrement();
        }

    }   

    public MyRunListener createListener() {
        return new Listener();
    }
}

package test;

import org.junit.runner.notification.Failure;

public class Detail  extends MyRunListener {
    public void testRunStarted(MyDescription description) throws Exception {
        println("==>JUnit4 started with description: \n" + description);
        println();

      }

      public void testRunFinished(MyResult result) throws Exception {
        println("==>JUnit4 finished with result: \n" + describe(result));
      }

      public void testStarted(MyDescription description) throws Exception {
        println("==>Test method started with description: " + description);
      }

      public void testFinished(MyDescription description) throws Exception {
        println("==>Test method finished with description: " + description);
        println();
      }

      public void testFailure(Failure failure) throws Exception {
        println("==>Test method failed with failure: " + failure);
      }

      public void testAssumptionFailure(Failure failure) {
        println("==>Test method assumption failed with failure: " + failure);
      }

      public void testIgnored(MyDescription description) throws Exception {
        println("==>Test method ignored with description: " + description);
        println();
      }

      private String describe(MyResult result) {
        StringBuilder builder = new StringBuilder();
        builder.append("\tRunCount: " + result.getRunCount())
            .append("\n");
        ;
        builder.append("\tRunTime: " + result.getRunTime())
            .append("\n");

        ;
        return builder.toString();
      }

      private void println() {
        System.out.println();
      }

      private void println(String content) {
        System.out.println(content);
      }
}

package test;

public class MyDescription {
    private  String fclassName;
    private  String fMethodName;

    public String getMethodName() {
        return fMethodName;
    }

    public String getClassName() {
        return fclassName;
    }

    @Override
    public String toString() {
        return getDisplayName();
    }

    /**
     * @return a user-understandable label
     */
    public String getDisplayName() {
        return formatDisplayName(fMethodName, fclassName);
    }

    private MyDescription(String className, String methodName) {
        fclassName = className;
        fMethodName = methodName;
    }

    public static MyDescription createMyDescriptionn(String className, String methodName) {
        return new MyDescription( className,  methodName);
    }

    private static String formatDisplayName(String name, String className) {
        return String.format("%s(%s)", name, className);
    }

}