并行（多线程）技术在软件术语里被定义为软件、操作系统或者程序可以并行地执行另外一段程序中多个部分或者子组件的能力。TestNG允许我们以并行（多线程）的方式来执行测试。这就意味着基于TestNG测试组件的配置，多个线程可以被同时启动然后分别执行各自的测试方法。相对于传统的单线程执行测试的方式，这种多线程方式拥有很大的优势，主要是它可以减少测试运行时间，并且可以验证某段代码在多线程环境中运行的正确性。

目录

1. 并行执行测试的优势
2. 如何并行地执行测试方法
3. 如何并行地执行测试类
4. 如何并行地执行同一测试套件内的各个测试组件
5. 如何配置需要在多线程环境中执行的测试方法

并行执行测试的优势

并行（多线程）执行测试可以给用户带来很多好处，主要包括以下两点：

1）减少了执行时间：并行测试也就意味着多个测试可以在同一时间被同时执行，从而减少了整体测试所花费的时间。

2）允许多个线程并行地测试同一个测试组件：有了这个特性，我们就能够写出相应的测试用例来验证应用程序中包含多线程部分的代码的正确性。

以上特性被广泛地应用在QA领域的自动化功能测试方面。通过简单的配置，QA人员就可以很轻松地使得他们的测试用例在多个浏览器或者操作系统中并行地执行。

TestNG提供了三种不同类型的配置方案来实现并行测试。

如何并行地执行测试方法

TestNG为我们提供了多种方式来实现并行测试，其中一种就是每一个独立的线程分别执行各自的测试方法。这种方式能够显著地减少测试执行时间，这是因为当有越多的测试方法被并行执行时，总体测试消耗时间将会越少。

package com.howtodoinjava.parallelism;    import org.testng.annotations.AfterMethod;  import org.testng.annotations.BeforeMethod;  import org.testng.annotations.Test;    public class ParallelMethodTest  {      @BeforeMethod      public void beforeMethod() {          long id = Thread.currentThread().getId();          System.out.println("Before test-method. Thread id is: " + id);      }        @Test      public void testMethodsOne() {          long id = Thread.currentThread().getId();          System.out.println("Simple test-method One. Thread id is: " + id);      }        @Test      public void testMethodsTwo() {          long id = Thread.currentThread().getId();          System.out.println("Simple test-method Two. Thread id is: " + id);      }        @AfterMethod      public void afterMethod() {          long id = Thread.currentThread().getId();          System.out.println("After test-method. Thread id is: " + id);      }  }

上述测试类包含了两个测试方法，每个测试方法在执行时都会在控制台中打印出一条信息。每个测试方法以及它们各自的beforeMehod、afterMethod方法都会通过Thread.currentThread.getId()这段代码打印出执行该测试方法的线程的ID。

在项目中新建一个名为methods-test-testng.xml的文件并将下述代码写入该文件中。

<suite name="Test-method Suite" parallel="methods" thread-count="2" >    <test name="Test-method test" group-by-instances="true">      <classes>        <class name="com.howtodoinjava.parallelism.ParallelMethodTest" />      </classes>    </test>  </suite>

在Eclipse中选中该文件并且以TestNG测试套件方式运行它。你将会在控制台中看到以下输出信息：

Before test-method. Thread id is: 10  Before test-method. Thread id is: 9  Simple test-method Two. Thread id is: 10  Simple test-method One. Thread id is: 9  After test-method. Thread id is: 10  After test-method. Thread id is: 9

注意：上述截图中的ThreadId可能与你本地控制台中输出的ThreadId不同，这是因为ThreadId的值是在程序运行时由JVM动态指派的。

从上述测试结果中我们可以很清晰地看出：上述两个测试方法以及各自相应的beforeMethod和afterMethod方法是在两个独立的线程中执行的。我们可以通过在控制台中输出的ThreadId来证明这一点。

如何并行地执行测试类

在下个例子中，我们会说明如何并行地执行测试类：同一个测试组件（test execution）中的各个测试类将会在独立的线程中并行地执行。

ParallelClassesTestOne.java

public class ParallelClassesTestOne  {      @BeforeClass      public void beforeClass() {          long id = Thread.currentThread().getId();          System.out.println("Before test-class. Thread id is: " + id);      }        @Test      public void testMethodOne() {          long id = Thread.currentThread().getId();          System.out.println("Sample test-method One. Thread id is: " + id);      }        @Test      public void testMethodTwo() {          long id = Thread.currentThread().getId();          System.out.println("Sample test-method Two. Thread id is: " + id);      }        @AfterClass      public void afterClass() {          long id = Thread.currentThread().getId();          System.out.println("After test-class. Thread id is: " + id);      }  }

ParallelClassesTestTwo.java

public class ParallelClassesTestTwo  {      @BeforeClass      public void beforeClass() {          long id = Thread.currentThread().getId();          System.out.println("Before test-class. Thread id is: " + id);      }        @Test      public void testMethodOne() {          long id = Thread.currentThread().getId();          System.out.println("Sample test-method One. Thread id is: " + id);      }        @Test      public void testMethodTwo() {          long id = Thread.currentThread().getId();          System.out.println("Sample test-method Two. Thread id is: " + id);      }        @AfterClass      public void afterClass() {          long id = Thread.currentThread().getId();          System.out.println("After test-class. Thread id is: " + id);      }  }

在项目中新建一个名为classes-test-testng.xml的文件并将下述代码写入该文件中：

<suite name="Test-class Suite" parallel="classes" thread-count="2" >    <test name="Test-class test" >      <classes>        <class name="com.howtodoinjava.parallelism.ParallelClassesTestOne" />        <class name="com.howtodoinjava.parallelism.ParallelClassesTestTwo" />      </classes>    </test>  </suite>

在Eclipse中选中该文件并且以TestNG测试套件方式运行它。你将会在控制台中看到以下输出信息：

Before test-class. Thread id is: 10  Before test-class. Thread id is: 9  Sample test-method One. Thread id is: 9  Sample test-method One. Thread id is: 10  Sample test-method Two. Thread id is: 10  After test-class. Thread id is: 10  Sample test-method Two. Thread id is: 9  After test-class. Thread id is: 9

package com.howtodoinjava.parallelism;    import org.testng.annotations.AfterClass;  import org.testng.annotations.AfterTest;  import org.testng.annotations.BeforeClass;  import org.testng.annotations.BeforeTest;  import org.testng.annotations.Parameters;  import org.testng.annotations.Test;    public class ParallelSuiteTest  {      String testName = "";        @BeforeTest      @Parameters({ "test-name" })      public void beforeTest(String testName) {          this.testName = testName;          long id = Thread.currentThread().getId();          System.out.println("Before test " + testName + ". Thread id is: " + id);      }        @BeforeClass      public void beforeClass() {          long id = Thread.currentThread().getId();          System.out.println("Before test-class " + testName + ". Thread id is: "                  + id);      }        @Test      public void testMethodOne() {          long id = Thread.currentThread().getId();          System.out.println("Sample test-method " + testName                  + ". Thread id is: " + id);      }        @AfterClass      public void afterClass() {          long id = Thread.currentThread().getId();          System.out.println("After test-method  " + testName                  + ". Thread id is: " + id);      }        @AfterTest      public void afterTest() {          long id = Thread.currentThread().getId();          System.out.println("After test  " + testName + ". Thread id is: " + id);      }  }

<suite name="Test-class Suite" parallel="tests" thread-count="2">      <test name="Test-class test 1">          <parameter name="test-name" value="test-method One" />          <classes>              <class name="com.howtodoinjava.parallelism.ParallelSuiteTest" />          </classes>      </test>      <test name="Test-class test 2">          <parameter name="test-name" value="test-method One" />          <classes>              <class name="com.howtodoinjava.parallelism.ParallelSuiteTest" />          </classes>      </test>  </suite>

Before test Test One. Thread id is: 9  Before test Test Two. Thread id is: 10  Before test-class Test One. Thread id is: 9  Before test-class Test Two. Thread id is: 10  Sample test-method Test One. Thread id is: 9  Sample test-method Test Two. Thread id is: 10  After test-method  Test Two. Thread id is: 10  After test-method  Test One. Thread id is: 9  After test  Test One. Thread id is: 9  After test  Test Two. Thread id is: 10

public class IndependentTest  {      @Test(threadPoolSize = 3, invocationCount = 6, timeOut = 1000)      public void testMethod()      {          Long id = Thread.currentThread().getId();          System.out.println("Test method executing on thread with id: " + id);      }  }

<suite name="Independent test Suite" >    <test name="Independent test">      <classes>       <class name="com.howtodoinjava.parallelism.IndependentTest" />      </classes>    </test>  </suite>

Test method executing on thread with id: 11  Test method executing on thread with id: 10  Test method executing on thread with id: 9  Test method executing on thread with id: 11  Test method executing on thread with id: 11  Test method executing on thread with id: 10