Webinar : Delivering Reliable Mobile Experiences through Elevated Quality
Close
TestNG: A Comprehensive Guide

TestNG: A Comprehensive Guide

June 6, 2022
 by 
Shinji Kanai

TestNG is a robust testing framework that helps you write comprehensive tests with ease. It offers many features including annotations, parameter injection, and built-in support for grouping tests. In this guide, we'll look at some of the key features of TestNG and how to use them to write better tests.

What is TestNG?

TestNG testing framework is one that offers several advantages over other frameworks, such as JUnit and NUnit. TestNG is designed to be more flexible and extensible, and it provides features that make it easier to write and run tests. In this guide, we'll look at some of the critical elements of TestNG and how to use them to write better tests.

Cedric Beust created TestNG in 2004. JUnit inspired him, and he wanted to create a more flexible and powerful testing framework. TestNG is an open-source project and is released under the Apache License 2.0.

TestNG is designed to be more flexible and extensible, and it provides features that make it easier to write and run tests.

Also check: What Are The Different Types Of Test Automation Frameworks?

Why use TestNG?

TestNG is a powerful testing framework that offers several advantages over other frameworks, such as JUnit and NUnit. Some of the key benefits of TestNG include:

  • Flexibility and extensibility: TestNG is more flexible than other frameworks, and it provides features that make it easier to It allows you run parallel execution of tests
  • Ease of use: TestNG is designed to be more user-friendly, as it defines dependency between one method on another (so if a failure occurs in the middle).
  • Comprehensive coverage: TestNG helps you write better, more extensive tests. In TestNG, we can group our methods together into groups with specific priorities for each purpose - for example: high/medium level checking versus low-level ones like logging exceptions or returning true conditions.

Why was TestNG developed?

JUnit is a popular testing framework often used in conjunction with TestNG. Although JUNit is a far older framework than TestNG, certain shortcomings of JUnit made TestNG come into the market. In this section, we'll look at some of the key differences between TestNG and JUnit:

Annotations: TestNG uses annotations to identify tests, set priorities, and configure other aspects of how the tests should be run. JUnit also uses annotations, but the annotations have different names and serve different purposes. For example, the @Test annotation in TestNG is used to identify a test method, while the @Test annotation in JUnit is used to configure how the test should be run.

Assertions: Assertions are used to verify that a specific condition is true. TestNG provides built-in support for assertions, while JUnit does not.

Parallel testing: TestNG supports parallel testing, which allows you to run multiple tests simultaneously. JUnit does not support parallel testing.

Reporting: TestNG provides flexible reporting features to help debug tests or provide information to stakeholders. JUnit also provides some reporting features, but they are not as robust as the ones in TestNG.

Data-driven testing: TestNG allows you to easily parameterize your tests, which is helpful for data-driven testing. JUnit does not have built-in support for data-driven testing, but some third-party libraries can be used to achieve this.

Also read: iOS Automation Testing - Top Frameworks

How To Install TestNG in eclipse and Configure TestNG

This section covers all the details regarding how to install and configure TestNG on your eclipse IDE. To make sure your tests are designed to run efficiently, follow the steps below to set up TestNG on your machine:

Install TestNG

To install TestNG, you can use the following command:


> Sudo apt-get install TestNG

Add TestNG to your project

To add TestNG to your project, you can add the following dependency to your pom.xml file:


<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>6.12.3</version> </dependency>

Configure TestNG in your project

To run tests with TestNG, you need to configure it in your project. You can do this by adding the following XML to your pom.xml file:


<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.19</version>
<configuration>
<suiteXmlFiles>
<suiteXmlFile/> </suiteXmlFiles></configuration></plugin></plugins></build>

Run TestNG tests

Once you have configured TestNG in your project, you can run your tests by using the following command:


mvn test

This will run all of the tests in your project. You can also use the following command to run a specific test:


mvn -Dtest=MyTest test

Key Features of TestNG Testing Framework

Some of the key features of TestNG include:

Annotations: TestNG uses annotations to identify tests, set priorities, and configure other aspects of how the tests should be run.

Parameter injection: TestNG allows you to inject parameters into your tests, which can be used to configure the test or provide data for the test.

Built-in support for grouping tests: With TestNG, you can group tests, which can be helpful if you want to run a subset of tests.

Flexible reporting: TestNG provides flexible reporting features, which can help debug tests or provide information to stakeholders.

Parallel testing in TestNG: Parallel testing in TestNG is well-supported, which can help you save time when running tests.

Data-driven testing: TestNG allows you to easily parameterize your tests, which can be helpful for data-driven testing.

TestNG Eclipse plugin: The TestNG Eclipse plugin makes it easy to create and run TestNG tests from within Eclipse.

Also check out: Choosing a Test Automation Tool - A Complete Guide

How to use TestNG Framework

Now that we've taken a look at some of the key features of TestNG let's see how we can use it to write better tests. This section will look at how to use annotations, parameters, and groups in TestNG.

Annotations

Annotation is a powerful feature of testing that allows you to specify how your test should be run. Annotations can be used to configure your test, set up dependencies, and group your tests. You can make your tests more modular and easier to maintain by using annotations.

TestNG uses annotations to identify tests, set priorities, and configure other aspects of how the tests should be run. This section will look at some of the most commonly used TestNG annotations.

@BeforeMethod

The @BeforeMethod annotation denotes a method that should be run before each test. This can be used to set up the environment for the test or perform any other actions that need to be done before the test is run.


public void setup() {
// do something
}

@AfterMethod 

The @AfterMethod annotation denotes a method that should be run after each test. This can be used to clean up the environment after the test is run or perform any other actions that need to be done after the test is finished.


public void tearDown() {
// do something
}

@Test 

The @Test annotation is used to denote a test method. This method will be executed when the test is run.


public void myTest() {
// do something
}

Attributes Used With Annotations In TestNG Framework

The following are some of the attributes that can be used with annotations in TestNG:

  • Priority: This attribute is used to set the priority of a test. The higher the priority, the sooner the test will be run.
  • timeout: This attribute is used to set the amount of time (in milliseconds) that should be allowed for the test to run. If the test takes longer than this, it will be aborted.
  • dependsOnMethods: This attribute specifies which methods the current method depends on. If one of the dependent methods fails, the current process will not be run.
  • groups: This attribute specifies which groups the current method belongs to. This can be helpful if you want to run a subset of tests.
  • dataProvider: This attribute specifies a data provider for the test. This can be used to provide data for the test from various sources.

Parameters

TestNG allows you to inject parameters into your tests, which can be used to configure the test or provide data for the test. In this section, we'll look at using parameters in TestNG.

Configuring parameters in TestNG

You can configure parameters in TestNG by using the <parameters> tag in your testng.xml file. For example, if you wanted to inject a parameter named "foo" with the value "bar," you would use the following XML:


<test>
<parameters>
<parameter name="foo" value="bar"/>
</parameters>
<classes>
// your test class here
</classes>
</test>

Injecting Parameters into Tests

Parameter injection is another valuable feature of TestNG that allows you to inject parameters into your tests. This can be used to provide data to your tests or to configure how your tests are run. Parameter injection is a powerful feature that can make your tests more flexible and easier to maintain.

Once you have configured parameters in TestNG, you can inject them into your tests by using the @Parameters annotation. For example, if you wanted to inject a parameter named "foo" into a test method, you would use the following annotation:


public void myTest(String foo) {
// do something with the foo parameter
}

Grouping Tests

TestNG also has built-in support for grouping tests. This allows you to group your tests and run them as a unit. This can be useful for organizing your tests or running a subset of your tests. TestNG also allows you to exclude certain groups of tests from being run.

This section will look at how to use groups in TestNG.

Configuring Groups in TestNG

You can configure groups in TestNG by using the <groups> tag in your testng.xml file. For example, if you wanted to create a group named "smoke-tests," you would use the following XML:


<test>
<groups>
<group name="smoke-tests"/>
</groups>
<classes>
// your test class here
</classes>
</test>

Running Tests in Groups

Once you have configured groups in TestNG, you can run tests in those groups by using the -groups command-line option. For example, if you wanted to run all tests in the "smoke-tests" group, you would use the following command:


java org.testng.TestNG -groups smoke-tests testng.xml

You can also use the groups attribute of the <class> tag to specify which groups a test class belongs to. For example, if you wanted to make sure that a test class belonged to the "smoke-tests" group, you would use the following XML:


<test>
<classes>
<class name="MyTestClass" groups="smoke-tests"/>
</classes>
</test>

Create a test suite with TestNG

To create a test suite with TestNG, you must create a testng.xml file. This file contains the configuration for your test suite. Once you have made the file, you can run your tests using the java org.testng.TestNG command-line option. For example, if you want to run all the tests in your test suite, you would use the following command:


java org.testng.TestNG testng.xml

You can also use the -suitename option to specify the name of your test suite. This can be useful if you have multiple test suites and you want to run them all at once. For example, if you have a test suite named "smoke-tests" and another called "regression-tests," you could run both suites by using the following command:


java org.testng.TestNG -suitename SmokeTests,RegressionTests testng.xml

TestNG also allows you to specify how your tests will be run. This can be useful if you have dependencies between your tests. For example, if you have a test that needs to run before another test, you can specify that by using the dependsOnMethods attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnMethods="myFirstTest")
public void mySecondTest() {
// do something else
}

How to run tests with TestNG

To run your tests, you can use the java org.testng.TestNG command-line option. This will run all of your tests in the order specified in your testng.xml file. You can also use the -Dtestng.xml option to select a different XML file. For example, if you wanted to run all the tests in your "smoke-tests" suite, you would use the following command:


java org.testng.TestNG -Dtestng.xml=smoke-tests.xml testng.xml

You can also use the -suitename option to specify the name of your test suite. This can be useful if you have multiple test suites and you want to run them all at once. For example, if you have a test suite named "smoke-tests" and another called "regression-tests," you could run both suites by using the following command:


java org.testng.TestNG -suitename SmokeTests,RegressionTests testng.xml

If you want to run a specific test or group of tests, you can use the -test names or -groups of options. For example, if you wanted to run the "myFirstTest" and "mySecondTest" tests, you would use the following command:


java org.testng.TestNG -testnames myFirstTest,mySecondTest testng.xml

If you want to run all the tests in a specific group, you can use the -groupsof option. For example, if you wanted to run all the tests in the "smoke-tests" group, you would use the following command:


java org.testng.TestNG -groupsof smoke-tests testng.xml

You can also use the groups attribute of the <class> tag to specify which groups a test class belongs to. For example, if you wanted to make sure that a test class belonged to the "smoke-tests" group, you would use the following XML:


<test>
<classes>
<class name="MyTestClass" groups="smoke-tests"/>
</classes>
</test>

Creating a test suite with TestNG is easy. You need to create a testng.xml file and specify the configuration for your tests. Once you have completed the file, you can run your tests using the java org.testng.TestNG command-line option. TestNG also allows you to specify the order in which your tests will be run and how they will be grouped. This makes it easy to create comprehensive test suites that can be efficiently run and maintained.

Using groups and dependencies in TestNG

TestNG allows you to specify how your tests will be run. This can be useful if you have dependencies between your tests. For example, if you have a test that needs to run before another test, you can specify that by using the dependsOnMethods attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnMethods="myFirstTest")
public void mySecondTest() {
// do something else
}

This allows you to easily create comprehensive test suites that can efficiently run and maintain. TestNG also will enable you to group your tests. This can be useful if you want to run a specific set of tests. For example, if you have a suite of Smoke Tests and Regression Tests, you can group your tests accordingly and run them separately.

To group your tests, you can use the groups attribute of the <class> tag. For example:


<test>
<classes>
<class name="MyTestClass" groups="smoke-tests"/>
</classes>
</test>

This will ensure that only the tests in the "smoke-tests" group are run. Using a comma-separated list, you can also specify that a test class belongs to multiple groups. For example:


<test>
<classes>
<class name="MyTestClass" groups="smoke-tests,regression-tests"/>
</classes>
</test>

This will ensure that the tests in both the "smoke-tests" and "regression-tests" groups are run. TestNG also allows you to exclude tests from a group. This can be useful if you want to run all the tests in a group except for a few.

To exclude tests from a group, you can use the excludeMethods attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(excludeMethods="myFirstTest")
public void mySecondTest() {
// do something else
}

This will make sure that only the "mySecondTest" is run. You can also use the excludeGroups attribute of the <class> tag to exclude a group of tests from running. For example:


<test>
<classes>
<class name="MyTestClass" excludeGroups="smoke-tests"/>
</classes>
</test>

This will ensure that all the tests in the "smoke-tests" group are excluded from running. TestNG also allows you to specify how your tests will be run. This can be useful if you have dependencies between your tests.

For example, if you have a test that needs to run before another test, you can specify that by using the dependsOnMethods attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnMethods="myFirstTest")
public void mySecondTest() {
// do something else
}

You can also use the dependsOnGroups attribute to specify a group of tests that need to be run before another group. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnGroups="myFirstTest")
public void mySecondTest() {
// do something else
}

This will ensure that the "myFirstTest" group is run before the "mySecondTest" group. You can also use the sequential attribute of the <class> tag to specify that the tests in a class need to be run in a specific order. For example:


<test>
<classes>
<class name="MyTestClass" sequential="true"/>
</classes>
</test>

This will ensure that the tests in the "MyTestClass" are run in the order they are defined. TestNG also allows you to specify the number of times a test should be run. This can be useful if you want to make sure that a test is stable before releasing it.

For example, if you want to run a test 10 times, you can use the invocationCount attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(invocationCount=10)
public void mySecondTest() {
// do something else
}

This will make sure that the "mySecondTest" is run ten times. You can also use the threadPoolSize attribute to specify how many threads should be used to run your tests. For example:


<test>
<classes>
<class name="MyTestClass" threadPoolSize="5"/>
</classes>
</test>

This will ensure that the tests in the "MyTestClass" are run using five threads. TestNG also allows you to specify the amount of time a test should take. This can be useful if you want to ensure that a test is taking the expected amount of time.

For example, if you want a test to finish within 10 seconds, you can use the invocationTimeOut attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(invocationTimeOut=10000)
public void mySecondTest() {
// do something else
}

This will ensure that the "mySecondTest" is given 10 seconds to finish before it is considered a failure. TestNG also allows you to specify the amount of time a test should wait for another test to complete. This can be useful if you have tests dependent on each other.

For example, if you want a test to wait for another test to finish before it starts, you can use the dependsOnMethods attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnMethods="myFirstTest", alwaysRun=true)
public void mySecondTest() {
// do something else
}

This will ensure that the "mySecondTest" is always run after the "myFirstTest" test has finished. TestNG also allows you to specify the amount of time a test should wait for another test to complete. This can be useful if you have tests dependent on each other.

For example, if you want a test to wait for another test to finish before it starts, you can use the dependsOnGroups attribute of the @Test annotation. For example:


public void myFirstTest() {
// do something
}

@Test(dependsOnGroups="myFirstTest")
public void mySecondTest() {
// do something else
}

This will ensure that the "mySecondTest" is run after the "myFirstTest" group has finished. You can also use the sequential attribute of the <class> tag to specify that the tests in a class need to be run in a specific order. For example:


<test>
<classes>
<class name="MyTestClass" sequential="true"/>
</classes>
</test>

How to debug tests with TestNG

Debugging tests with TestNG is a little different than debugging tests with JUnit. You can use the fail() method to stop a test and print the stack trace with JUnit. With TestNG, you can use the fail(String message) method to stop a test and print the message. For example:


public void myFirstTest() {
// do something
}

@Test(invocationCount=10)
public void mySecondTest() {
// do something else
}

The "mySecondTest" will run ten times, but the "myFirstTest" will only run once. To debug the "myFirstTest," you can use the fail(String message) method to stop the test and print the message. For example:


public void myFirstTest() {
fail("myFirstTest");
}

@Test(invocationCount=10)
public void mySecondTest() {
// do something else
}

This will ensure that the "myFirstTest" is only run once and that the "mySecondTest" is never run. You can also use the skipFailedInvocations attribute of the <class> tag to specify that tests should be skipped if they fail. For example:


<test>
<classes>
<class name="MyTestClass" skipFailedInvocations="true"/>
</classes>
</test>

This will ensure that the "mySecondTest" is only run if the "myFirstTest" passes. If the "myFirstTest" fails, the "mySecondTest" will be skipped. You can also use the skipFailedInvocations attribute of the <class> tag to specify that tests should be omitted if they fail. For example:


<test>
<classes>
<class name="MyTestClass" skipFailedInvocations="true"/>
</classes>
</test>

Important points to remember while using TestNG

Here are some things to keep in mind while using TestNG for getting the best out of the framework:

  • Use the annotation @DataProvider to create test data for your tests. This annotation will help you to write more comprehensive and robust tests.
  • Use the annotation @Parameters to inject parameters into your tests. This annotation can inject values from a configuration file or the command line into your tests.
  • Use the groups attribute of the <class> tag to specify that a test class should be run in a specific order. This can be helpful when you have tests that are dependent on each other.
  • Use the dependsOnMethods attribute of the @Test annotation to specify that a test should wait for another test to finish before it starts. This can be useful when you have tests dependent on each other.
  • Use the sequential attribute of the <class> tag to specify that the tests in a class need to be run in a specific order. This can be helpful when you have tests dependent on each other.
  • Use the skipFailedInvocations attribute of the <class> tag to specify that tests should be skipped if they fail. This can be helpful when you have tests dependent on each other.
  • Use the annotation @Factory to create test instances dynamically. This annotation can be used to develop tests that are not known at compile time.
  • Use the annotation @Listeners to add listeners to your tests. This annotation can be used to add custom behavior to your tests.
  • Use the annotation @Test(invocationCount=n) to run a test multiple times. This can be useful for tests that need to be run multiple times.

The Bottom Line

TestNG is a framework that has certain advantages over JUnit. It allows us to create easy-to understand HTML reports which are generated automatically, making it easier for developers with limited technical knowledge of programming languages like Java or C# as well nonprofessional ones who may be just starting out in this field. It is perfect for all the developers and testers who still want control over what they're doing when testing their apps on different devices from across various versions. If you haven’t tried TestNG yet, you should as it is one of the best testing Frameworks out there.

TestNG Frequently Asked Question (FAQs)

Q: What is TestNG?

A: TestNG is a powerful testing framework that helps you write better, more comprehensive tests. It offers many features that make it easier to write and run tests, including annotations, parameter injection, and built-in support for grouping tests.

Q: What are the critical differences between TestNG and Selenium?

A: TestNG is a robust testing framework that helps you write better, more comprehensive tests. It offers many features that make it easier to write and run tests, including annotations, parameter injection, and built-in support for grouping tests. Selenium is a web automation tool that can automate web browser interactions.

Q: How can TestNG be used to write better tests?

A: TestNG can be used to write better tests by providing features such as annotations, parameter injection, and built-in support for grouping tests. These features can help you write more comprehensive and practical tests.

Q: What is the difference between TestNG and JUnit?

A: TestNG and JUnit are both testing frameworks that can be used to write and run tests. However, there are some critical differences between these two frameworks. TestNG uses annotations to identify tests, set priorities, and configure other aspects of how the tests should be run. JUnit also uses annotations, but the annotations have different names and serve different purposes.

Q: Which methods can be tested by TestNG?

A: TestNG can test public, private, and protected methods. It can also be used to test static and non-static methods.

Q: What is the postcondition in TestNG?

A: A postcondition is a condition that must be met after a test has run. In TestNG, you can use the assertPostcondition() method to verify that a postcondition has been completed.

Q: What is the sequence of execution of the annotations in TestNG?

A: The sequence of execution of the annotations in TestNG is as follows:

1) BeforeSuite

2) BeforeTest

3) BeforeClass

4) BeforeMethod

5) Test

6) AfterMethod

7) AfterClass

8) AfterTest

9) AfterSuite