TestNG Interview Questions

How do you rerun only failed tests in TestNG?

DataProvider vs @Parameters — when do you use each?

@Parameters injects static values from testng.xml (browser, env); @DataProvider supplies dynamic, multi-row test data from code, Excel, JSON or DB.

In what order do TestNG annotations execute?

@BeforeSuite → @BeforeTest → @BeforeClass → @BeforeMethod → @Test → @AfterMethod → @AfterClass → @AfterTest → @AfterSuite, with @BeforeGroups/@AfterGroups around grouped tests.

How do you run data-driven tests with @DataProvider, and when do you use an external file?

@DataProvider returns Object[][] (or an Iterator) that TestNG feeds into the test method once per row; move data to Excel/CSV/JSON when non-engineers own it or the set is large.

How do you configure parallel execution in TestNG?

Set parallel (methods, classes, tests or instances) plus thread-count in testng.xml, and make every shared resource thread-safe — driver in ThreadLocal, no static state, unique test data per thread.

How do you implement retry for flaky tests with IRetryAnalyzer, and when is it wrong?

Implement IRetryAnalyzer with a max-retry counter and attach it globally via an IAnnotationTransformer; use it for known infrastructure flakiness only, never to hide product bugs.

What do TestNG listeners give you, and which ones do you actually implement?

ITestListener for screenshots/logging on failure, ISuiteListener for report lifecycle, IAnnotationTransformer for retries, and IInvokedMethodListener for per-step logging.

What is annotation lifecycle, and why does it matter in TestNG?

annotation lifecycle is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply annotation lifecycle in a production TestNG project?

Apply annotation lifecycle through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is test groups, and why does it matter in TestNG?

test groups is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply test groups in a production TestNG project?

Apply test groups through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is DataProvider, and why does it matter in TestNG?

DataProvider is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply DataProvider in a production TestNG project?

Apply DataProvider through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is parameters, and why does it matter in TestNG?

parameters is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply parameters in a production TestNG project?

Apply parameters through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is dependsOnMethods, and why does it matter in TestNG?

dependsOnMethods is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply dependsOnMethods in a production TestNG project?

Apply dependsOnMethods through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is dependsOnGroups, and why does it matter in TestNG?

dependsOnGroups is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply dependsOnGroups in a production TestNG project?

Apply dependsOnGroups through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is priority, and why does it matter in TestNG?

priority is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply priority in a production TestNG project?

Apply priority through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is parallel modes, and why does it matter in TestNG?

parallel modes is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply parallel modes in a production TestNG project?

Apply parallel modes through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is thread count, and why does it matter in TestNG?

thread count is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply thread count in a production TestNG project?

Apply thread count through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is listeners, and why does it matter in TestNG?

listeners is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply listeners in a production TestNG project?

Apply listeners through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is retry analyzer, and why does it matter in TestNG?

retry analyzer is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply retry analyzer in a production TestNG project?

Apply retry analyzer through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is ITestContext, and why does it matter in TestNG?

ITestContext is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply ITestContext in a production TestNG project?

Apply ITestContext through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is soft assertions, and why does it matter in TestNG?

soft assertions is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply soft assertions in a production TestNG project?

Apply soft assertions through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is factories, and why does it matter in TestNG?

factories is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply factories in a production TestNG project?

Apply factories through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is suite XML, and why does it matter in TestNG?

suite XML is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply suite XML in a production TestNG project?

Apply suite XML through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is method interceptors, and why does it matter in TestNG?

method interceptors is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply method interceptors in a production TestNG project?

Apply method interceptors through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is invocation count, and why does it matter in TestNG?

invocation count is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply invocation count in a production TestNG project?

Apply invocation count through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is timeouts, and why does it matter in TestNG?

timeouts is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply timeouts in a production TestNG project?

Apply timeouts through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is expected exceptions, and why does it matter in TestNG?

expected exceptions is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply expected exceptions in a production TestNG project?

Apply expected exceptions through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is reporters, and why does it matter in TestNG?

reporters is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply reporters in a production TestNG project?

Apply reporters through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is configuration failures, and why does it matter in TestNG?

configuration failures is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply configuration failures in a production TestNG project?

Apply configuration failures through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is alwaysRun, and why does it matter in TestNG?

alwaysRun is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply alwaysRun in a production TestNG project?

Apply alwaysRun through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.

What is data-provider parallelism, and why does it matter in TestNG?

data-provider parallelism is a core TestNG concept used to make testing decisions more accurate, repeatable, and aligned with product risk.

How would you apply data-provider parallelism in a production TestNG project?

Apply data-provider parallelism through an explicit, repeatable design: define the expected behavior, automate the highest-risk path, capture useful diagnostics, and verify the result against a stable oracle.