TestNG: Run tests sequentially with @DataProvider inside one test class

Many java developers and automation test engineers use TestNG as a testing framework in their job. I’m not an exception. This is an obvious choice because TestNG provides very powerful set of tools which makes working with all kinds of tests easier. To prove this I’ll show you in this article how can be solved one not trivial task.

The problem

How to run tests within a single class in particular order with different data sets? Well looks like I exposed a formulation of the problem in one sentence. But if you ask me to present this sentence in a more strict form I’ll provide the following list:

• Multiple test methods
• One test class
• Sequence run
• Different data sets for each test method

Summarizing here is an abstract schema of the problem:

TestClass {
    firstTest(String testData)
    secondTest(String testData)
    thirdTest(String testData)
}

TestDataSets {
    "string 1"
    "string 2"
}

Running of these tests should leads to the result:

firstTest(string 1)
secondTest(string 1)
thirdTest(string 1)

firstTest(string 2)
secondTest(string 2)
thirdTest(string 2)

After the problem was highlighted and explained, we can go ahead to its solution.

TestNG realisation

I’ll use the most simplified code constructions but you can use such approach customizing it with some specific logic.

package kill.me.later;

import static org.testng.Assert.assertTrue;

import org.testng.annotations.Test;

public class SomeTest {
	
	private int id = 0;
	private String account = "";
	
	public SomeTest(int id, String account) {
		this.id = id;
		this.account = account;
	}
	
	@Test
	public void firstTest() {
		System.out.println("Test #1 with data: "+id+". "+account);
		assertTrue(true);
	}
	
	@Test
	public void secondTest() {
		System.out.println("Test #2 with data: "+id+". "+account);
		assertTrue(true);
	}
	
	@Test
	public void thirdTest() {
		System.out.println("Test #3 with data: "+id+". "+account);
		assertTrue(true);
	}

}

Examining the code above, everyone can notice that I use a regular TestNG @Test annotation applied to void methods. Also I declared a constructor, but its purpose will be discussed later.
TestNG has very useful annotations – @Factory and @DataProvider. I recommend to read about them on the official TestNG documentation site. While you are reading about these annotations I’ll proceed with practical part:

package kill.me.later;

import org.testng.annotations.DataProvider;
import org.testng.annotations.Factory;

public class SampleFactory {
	
	@Factory(dataProvider="dp")
	public Object[] createInstances(int id, String account) {
		return new Object[] {new SomeTest(id, account)};
	}
	
	@DataProvider(name="dp")
	public static Object[][] dataProvider() {
		Object[][] dataArray = {
				{1, "user1"},
				{2, "user2"}
		};
		return dataArray;
	}

}

The last code snippet provides run of each test method from the SomeTest class with data sets declared in the dataProvider. But if you try to run the SampleFactory class with help of TestNG you will not get the execution order of the test methods from the “The problem” section. In order to achieve the sequential execution test methods order you need to use TestNG XML launcher:

< !DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd" >

<suite name="LocalSuite" verbose="1">
	<test name="ParticularTest" group-by-instances="true">
		<classes>
			<class name="kill.me.later.SampleFactory"></class>
		</classes>
	</test>
</suite>

Pay your attention to the group-by-instances parameter. Exactly it provides so desirable sequence order for the test methods execution. So now you can easily organize your tests for this kind of DDT runs.