Working example of DataProvider in TestNG?

In the Automation Testing we see a lot of time that the we can use the same Testing method with different Parameter to cover the maximum test coverage and we can cover the boundary conditions as well

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

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)

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]