DataProvider with external data in Selenium Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of DataProvider with CSV external data

Given the following TestNG test code using a DataProvider that reads from a CSV file, what will be the output when the test runs?

Selenium Java

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.List;

public class CsvDataProviderTest {

    @DataProvider(name = "csvData")
    public Object[][] readCsv() throws Exception {
        List<Object[]> data = new ArrayList<>();
        try (BufferedReader br = new BufferedReader(new FileReader("testdata.csv"))) {
            String line;
            while ((line = br.readLine()) != null) {
                String[] parts = line.split(",");
                data.add(new Object[]{parts[0], Integer.parseInt(parts[1])});
            }
        }
        return data.toArray(new Object[0][]);
    }

    @Test(dataProvider = "csvData")
    public void testWithCsvData(String name, int age) {
        System.out.println(name + "-" + age);
    }
}

A John-30\nJane-25\nBob-40

B John-30\nJane-25\nBob-40\nnull-0

C Compilation error due to missing throws declaration

D Runtime error: NumberFormatException

💡 Hint

Think about how the CSV lines are read and parsed into the DataProvider array.

The DataProvider reads each line from the CSV file, splits by comma, and converts the second value to int. The test prints each pair correctly. No extra null or errors occur if the CSV is well-formed.

❓ assertion

intermediate

Correct assertion for DataProvider test with Excel data

You have a TestNG test using a DataProvider that reads user credentials from an Excel file. Which assertion correctly verifies that the username is not empty in the test method?

Selenium Java

@Test(dataProvider = "excelData")
public void loginTest(String username, String password) {
    // assertion here
}

A Assert.assertTrue(username.length() > 0);

B Assert.assertFalse(username.isEmpty());

C Assert.assertNotNull(username);

D Assert.assertEquals(username, "");

💡 Hint

Check which assertion ensures the username string is not empty.

Assert.assertFalse(username.isEmpty()) correctly asserts that username is not empty. Option B only checks for null, but username could be empty string. Option B works but is less readable. Option B asserts username is empty, which is wrong.

🔧 Debug

advanced

Identify the error in DataProvider reading JSON file

This DataProvider reads test data from a JSON file. What error will occur when running this code?

Selenium Java

import org.testng.annotations.DataProvider;
import java.nio.file.Files;
import java.nio.file.Paths;
import org.json.JSONArray;
import org.json.JSONObject;

@DataProvider(name = "jsonData")
public Object[][] getData() throws Exception {
    String content = Files.readString(Paths.get("data.json"));
    JSONArray arr = new JSONArray(content);
    Object[][] data = new Object[arr.length()][2];
    for (int i = 0; i < arr.length(); i++) {
        JSONObject obj = arr.getJSONObject(i);
        data[i][0] = obj.getString("username");
        data[i][1] = obj.getString("password");
    }
    return data;
}

A ArrayIndexOutOfBoundsException at runtime

B NullPointerException at runtime

C Compilation error due to missing return type

D No error, runs successfully

💡 Hint

Check the for loop boundary condition carefully.

The for loop uses i <= arr.length(), but valid indices are 0 to arr.length() - 1. This causes ArrayIndexOutOfBoundsException when i equals arr.length().

❓ framework

advanced

Best practice for external DataProvider file location

In a Selenium TestNG project, where is the best place to store external test data files (like CSV, Excel) to ensure portability and easy access in DataProviders?

A In a temporary folder outside the project

B In the project root directory

C Inside the src/main/java package folder

D Inside src/test/resources folder

💡 Hint

Think about Maven/Gradle standard project structure and resource loading.

The src/test/resources folder is the standard location for test resources. Files here are included in the test classpath and easily accessed by DataProviders. Other locations are not standard or portable.

🧠 Conceptual

expert

Why use external data sources with DataProvider?

Which is the main advantage of using external data sources (like CSV, Excel, JSON) with TestNG DataProviders instead of hardcoding test data inside the test class?

A It reduces test execution time significantly

B It guarantees zero test failures

C It allows easy maintenance and scalability of test data without code changes

D It automatically generates test reports

💡 Hint

Think about how test data changes affect test code.

Using external data sources separates test data from code, making it easier to update or add test cases without modifying code. This improves maintainability and scalability. It does not directly affect execution time, failure rates, or reporting.

Practice

1. What is the main purpose of using @DataProvider in Selenium tests?

easy

A. To locate web elements on the page

B. To create a new browser instance for each test

C. To generate test reports automatically

D. To run the same test multiple times with different input data

Solution

1. Step 1: Understand the role of DataProvider

   @DataProvider is used to supply different sets of data to a test method so it can run multiple times with varied inputs.

2. Step 2: Compare options with this purpose

   Only To run the same test multiple times with different input data describes running the same test multiple times with different data, which matches the purpose of DataProvider.

3. Final Answer:

   To run the same test multiple times with different input data -> Option D

4. Quick Check:

   DataProvider = multiple test runs with data [OK]

Hint: DataProvider runs tests repeatedly with varied inputs [OK]

Common Mistakes:

• Confusing DataProvider with browser setup
• Thinking DataProvider locates elements
• Assuming DataProvider generates reports

2. Which of the following is the correct syntax to declare a DataProvider method that reads data from an external CSV file?

easy

A. @DataProvider(name = "csvData")
public Object[][] getData() {
// code to read CSV and return Object[][]
}

B. @DataProvider
public void getData() {
// code to read CSV
}

C. @DataProvider(name = "csvData")
public void getData() {
return new Object[][] {};
}

D. @DataProvider(name = "csvData")
public Object getData() {
// code to read CSV
}

Solution

1. Step 1: Check DataProvider method signature

   A DataProvider method must return Object[][] and be public. @DataProvider(name = "csvData") public Object[][] getData() { // code to read CSV and return Object[][] } matches this.

2. Step 2: Verify other options

   @DataProvider public void getData() { // code to read CSV } returns void, which is invalid. @DataProvider(name = "csvData") public void getData() { return new Object[][] {}; } returns void but tries to return data, invalid. @DataProvider(name = "csvData") public Object getData() { // code to read CSV } returns Object, not Object[][], invalid.

3. Final Answer:

   @DataProvider(name = "csvData") public Object[][] getData() { // code to read CSV and return Object[][] } -> Option A

4. Quick Check:

   DataProvider method returns Object[][] [OK]

Hint: DataProvider must return Object[][] and be public [OK]

Common Mistakes:

• Using void return type for DataProvider
• Returning Object instead of Object[][]
• Missing @DataProvider annotation name

3. Given the following DataProvider method reading CSV data, what will be the output when the test runs?

@DataProvider(name = "csvData")
public Object[][] getData() {
  return new Object[][] {
    {"user1", "pass1"},
    {"user2", "pass2"}
  };
}

@Test(dataProvider = "csvData")
public void loginTest(String username, String password) {
  System.out.println(username + ":" + password);
}

medium

A. user1
pass1
user2
pass2

B. user1:pass1
user2:pass2

C. user1pass1user2pass2

D. Compilation error due to DataProvider

Solution

1. Step 1: Understand DataProvider data structure

   The DataProvider returns two sets of data: {"user1", "pass1"} and {"user2", "pass2"}.

2. Step 2: Analyze test method output

   The test runs twice, printing username and password separated by a colon each time, resulting in two lines: "user1:pass1" and "user2:pass2".

3. Final Answer:

   user1:pass1 user2:pass2 -> Option B

4. Quick Check:

   Each data set prints username:password [OK]

Hint: Each data row runs test once, printing combined values [OK]

Common Mistakes:

• Expecting all data printed in one line
• Confusing array structure with output format
• Assuming compilation error without reason

4. Identify the error in this DataProvider method that reads data from a CSV file:

@DataProvider(name = "csvData")
public Object[][] getData() {
  List lines = readCsv("data.csv");
  Object[][] data = new Object[lines.size()][];
  for (int i = 0; i <= lines.size(); i++) {
    data[i] = lines.get(i);
  }
  return data;
}

medium

A. The loop condition should be < instead of <= to avoid IndexOutOfBoundsException

B. The method should return List instead of Object[][]

C. The DataProvider annotation is missing parameters

D. The data array size is incorrect and should be lines.size() + 1

Solution

1. Step 1: Analyze the for loop condition

   The loop runs from i = 0 to i <= lines.size(), which means it tries to access data[lines.size()] causing IndexOutOfBoundsException.

2. Step 2: Correct the loop condition

   The loop should run while i < lines.size() to stay within valid array indices.

3. Final Answer:

   The loop condition should be < instead of <= to avoid IndexOutOfBoundsException -> Option A

4. Quick Check:

   Loop index must be less than array size [OK]

Hint: Loop index must be less than array length, not less or equal [OK]

Common Mistakes:

• Using <= in loops causing index errors
• Returning wrong data type from DataProvider
• Misunderstanding DataProvider annotation usage

5. You want to use a DataProvider that reads test data from a CSV file and filters out rows where the first column is empty before running tests. Which approach correctly implements this?

hard

A. Return the entire CSV data as Object[][] without filtering, and filter inside the test method

B. Filter rows after test execution by skipping tests with empty first column

C. Read all CSV rows into a List, filter out rows with empty first column, then convert filtered list to Object[][] and return

D. Use a DataProvider that returns null for rows with empty first column

Solution

1. Step 1: Understand filtering before test execution

   Filtering data in the DataProvider ensures only valid data sets run tests, keeping tests clean and efficient.

2. Step 2: Implement filtering in DataProvider

   Read CSV into a list, remove rows with empty first column, then convert to Object[][] to supply filtered data to tests.

3. Final Answer:

   Read all CSV rows into a List, filter out rows with empty first column, then convert filtered list to Object[][] and return -> Option C

4. Quick Check:

   Filter data in DataProvider before tests run [OK]

Hint: Filter data inside DataProvider, not inside test method [OK]

Common Mistakes:

• Filtering data inside test method instead of DataProvider
• Returning null for filtered rows causing errors
• Skipping tests after execution instead of filtering input