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.