Data providers for parameterization in Selenium Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a TestNG DataProvider with multiple parameters

Consider the following TestNG test method using a DataProvider. What will be the output when the test runs?

Selenium Java

import org.testng.annotations.*;

public class TestClass {
  @DataProvider(name = "dp")
  public Object[][] dataProvider() {
    return new Object[][] {
      {"user1", 1},
      {"user2", 2}
    };
  }

  @Test(dataProvider = "dp")
  public void testMethod(String username, int id) {
    System.out.println(username + "-" + id);
  }
}

A user1-2\nuser2-1

B Compilation error due to wrong DataProvider signature

C user1\n1\nuser2\n2

D user1-1\nuser2-2

💡 Hint

Look at how the DataProvider returns a 2D Object array and how parameters map to method arguments.

The DataProvider returns two sets of parameters: {"user1", 1} and {"user2", 2}. The test method receives these as (username, id) pairs and prints them concatenated with a dash. So the output lines are 'user1-1' and 'user2-2'.

❓ assertion

intermediate

Correct assertion for parameterized test with DataProvider

You have a test method that receives two integers from a DataProvider and should assert their sum equals 10. Which assertion is correct?

Selenium Java

@Test(dataProvider = "numbers")
public void testSum(int a, int b) {
  // assertion here
}

@DataProvider(name = "numbers")
public Object[][] numbers() {
  return new Object[][] {
    {7, 3},
    {5, 5},
    {6, 4}
  };
}

A Assert.assertEquals(a + b, 10);

B Assert.assertTrue(a + b == 10);

C Assert.assertEquals(10, a + b);

D Assert.assertFalse(a + b != 10);

💡 Hint

Remember the order of actual and expected in Assert.assertEquals(actual, expected).

In TestNG, Assert.assertEquals expects the first argument as actual value and second as expected. So Assert.assertEquals(a + b, 10) is correct. Option A has reversed parameters which can cause confusing messages. Options B and D are logically correct but less clear.

🔧 Debug

advanced

Identify the error in DataProvider method

What error will occur when running this TestNG test with the given DataProvider?

Selenium Java

@DataProvider(name = "dp")
public Object dataProvider() {
  return new Object[] {"test1", "test2"};
}

@Test(dataProvider = "dp")
public void testMethod(String input) {
  System.out.println(input);
}

A Test runs successfully printing test1 and test2

B java.lang.IllegalArgumentException: DataProvider must return Object[][] or Iterator<Object[]>

C Compilation error due to missing @Test annotation

D NullPointerException at testMethod

💡 Hint

Check the return type of the DataProvider method and what TestNG expects.

TestNG requires DataProvider methods to return Object[][] or Iterator to supply multiple parameter sets. Returning Object[] causes IllegalArgumentException at runtime.

❓ framework

advanced

Best practice for DataProvider with external data source

You want to read test data from a CSV file to use in a TestNG DataProvider. Which approach is best?

A Read the CSV file inside the DataProvider method and return Object[][] with parsed data

B Hardcode CSV data inside the test method and ignore DataProvider

C Manually copy CSV data into Java arrays and return from DataProvider

D Use @Parameters annotation instead of DataProvider for CSV data

💡 Hint

Think about maintainability and reusability of test data.

Reading CSV inside DataProvider allows dynamic, maintainable data-driven tests. Hardcoding or manual copying is error-prone and not scalable. @Parameters is for simple fixed parameters, not data-driven tests.

🧠 Conceptual

expert

Why use DataProvider over @Parameters in TestNG?

Which statement best explains the advantage of using DataProvider for parameterization compared to @Parameters?

A DataProvider can only pass primitive types, @Parameters supports complex objects.

B @Parameters allows dynamic data generation at runtime, DataProvider requires static data only.

C DataProvider supports multiple sets of parameters for the same test method, enabling data-driven testing; @Parameters supports only single set from XML.

D @Parameters is faster and preferred for large data sets over DataProvider.

💡 Hint

Consider how many test runs each approach can generate from given data.

DataProvider can supply multiple parameter sets, running the test multiple times with different data (data-driven). @Parameters reads fixed parameters from XML and runs test once per method.