How to use DataProvider in TestNG?

There are multiple cases, when we have to validate our use-cases where the logic should be same but the test data is different and we must validate our logic for multiple parameters. TestNG provides a very easy way of passing parameters using the DataProvider. In this article we are going to learn how to use DataProvider with @Test.

A Data Provider is a method on your class that returns an array of array of objects.

How to pass String parameter in DataProvider:

package com.tutorial.testng.parameters;

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

public class DataProviderInTest {

	@Test(dataProvider = "userDetails")
	public void testUserDetails(String user, String password) {
		System.out.println("Test User: " + user + " Password: " + password);
	}

	@DataProvider(name = "userDetails")
	public Object[][] userDetails() {

		return new Object[][] {
			{ "user1", "password1" },
			{ "user2", "password2" },
			{ "user3", "password3" } };
	}
}

Output:

Test User: user1 Passsword: password1
Test User: user2 Passsword: password2
Test User: user3 Passsword: password3

dataprovider-testng-result

I have used String here in this example but you can pass other data types also using the data provider.

How to pass Class Object in DataProvider:

Using DataProvider you can pass Class object parameters.So we need to create multiple objects of a particular Class and passed as DataProvider to our @Test method.

Step 1: Create a User Class POJO which has User and Password Value.

package com.tutorial.testng.parameters;

public class User {

	private String user;
	private String password;

	public String getUser() {
		return user;
	}

	public String getPassword() {
		return password;
	}

	public User setUser(String user) {
		this.user = user;
		return this;
	}

	public User setPassword(String password) {
		this.password = password;
		return this;
	}
}

Step 2: Now create a Test Class with DataProvider and pass multiple User.java object and print the user details in our TestCase.

package com.tutorial.testng.parameters;

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

public class DataProviderWithObjectTest {

	@Test(dataProvider = "userDetails")
	public void testUserDetails(User users) {
		System.out.println("Test User: " + users.getUser() + " Password: " + users.getPassword());
	}

	@DataProvider(name = "userDetails")
	public Object[][] userDetails() {

		return new Object[][] {
			{ new User().setUser("user1").setPassword("password1") },
			{ new User().setUser("user2").setPassword("password2") },
			{ new User().setUser("user3").setPassword("password3") }, };
	}
}

Output:

Test User: user1 Password: password1
Test User: user2 Password: password2
Test User: user3 Password: password3
PASSED: testUserDetails(com.tutorial.testng.parameters.User@2f686d1f)
PASSED: testUserDetails(com.tutorial.testng.parameters.User@69ea3742)
PASSED: testUserDetails(com.tutorial.testng.parameters.User@3159c4b8)

dataprovider-object-testng-results

What If you pass wrong No of arguments in DataProvider:

DataProvider expectes you to pass and receive the same set of arguments, If there is a mismatch in the arguments, It will thrown an exception and TestCases will not Run.

There is org.testng.internal.reflect.DataProviderMethodMatcher class in testNG used for verification, using a method getConformingArguments() for verifying the no of arguments.

@Override
public Object[] getConformingArguments(){
  if (ThreeStateBoolean.NONE.equals(getConforms())) {
    conforms();
  }
  if (matchingMatcher != null) {
    return matchingMatcher.getConformingArguments();
  }
  throw new MethodMatcherException("Data provider mismatch", getContext().getMethod(), getContext().getArguments());
}
}

In this Example below we will pass an extra Argument from the DataProvider but will not accept that argument in our @Test method and Test will fail with exception.

package com.tutorial.testng.parameters;

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

public class DataProviderFailure {

	@Test(dataProvider = "userDetails")
	public void testUserDetails(String user, String password) {
		System.out.println("Test User: " + user + " Password: " + password);
	}

	@DataProvider(name = "userDetails")
	public Object[][] userDetails() {
		return new Object[][] { { "user1","password1","extraValue" },
			                { "user2","password2","extraValue" },
			                { "user3","password3","extraValue" } };
	}
}

Output Exception:

org.testng.internal.reflect.MethodMatcherException:
Data provider mismatch
Method: testUserDetails([Parameter{index=0, type=java.lang.String, declaredAnnotations=[]}, Parameter{index=1, type=java.lang.String, declaredAnnotations=[]}])
Arguments: [(java.lang.String)user1,(java.lang.String)password1,(java.lang.String)application]