Question 1

What is the difference between load testing, stress testing, and spike testing?

Accepted Answer

The 30-Second Answer: Load testing validates system behavior under expected normal and peak loads. Stress testing pushes the system beyond its limits to find breaking points and observe failure modes. Spike testing evaluates how the system handles sudden, dramatic increases in load and whether it recovers gracefully. The 2-Minute Answer (If They Want More): Load testing is the most common type of performance testing.

Question 2

What is the difference between solitary and sociable unit tests?

Accepted Answer

The 30-Second Answer: Solitary unit tests (classical/mockist style) test a class in complete isolation using test doubles for all dependencies. Sociable unit tests (Detroit/classicist style) allow the unit under test to use its real collaborators, only mocking external systems like databases or APIs. The 2-Minute Answer (If They Want More): The solitary vs. sociable distinction represents two different philosophies in unit testing.

Question 3

What is the difference between unit testing and integration testing?

Accepted Answer

The 30-Second Answer: Unit tests verify individual components in complete isolation using mocks and stubs, while integration tests verify that multiple components work together correctly using real or realistic dependencies. Unit tests are faster and more focused, while integration tests provide more confidence about system behavior. The 2-Minute Answer (If They Want More): The fundamental difference lies in scope and dependencies.

Question 4

What is the difference between integration tests and end-to-end tests?

Accepted Answer

The 30-Second Answer: Integration tests verify that multiple components work together correctly, focusing on specific integrations like a service with a database or API. End-to-end tests verify complete user workflows through the entire system from UI to database, simulating real user scenarios. E2E tests are slower, more brittle, but provide the most confidence. The 2-Minute Answer (If They Want More): The distinction lies in scope, perspective, and what you're trying to validate.

Question 5

What is the difference between mocks, stubs, fakes, and spies?

Accepted Answer

The 30-Second Answer: Stubs provide predetermined answers to calls, mocks verify that specific calls were made with expected arguments, fakes are working implementations with shortcuts (like an in-memory database), and spies record information about how they were called. The key difference is whether they're about state verification (stubs, fakes) or behavior verification (mocks, spies).

Question 6

What is the difference between code coverage and test effectiveness?

Accepted Answer

The 30-Second Answer: Code coverage measures which code was executed during tests, while test effectiveness measures whether tests actually validate correct behavior and catch bugs. You can have 100% coverage with poor assertions that miss bugs, or lower coverage with highly effective tests that thoroughly validate critical logic. The 2-Minute Answer (If They Want More): Code coverage and test effectiveness measure fundamentally different things, and conflating them is a common mistake.

Question 7

What is performance testing?

Accepted Answer

The 30-Second Answer: Performance testing is the practice of evaluating how a system performs under various workloads, measuring metrics like response time, throughput, resource utilization, and stability. It helps identify bottlenecks, ensure the system meets performance requirements, and verify it can handle expected user loads before production deployment.

Question 8

What is baseline testing in performance testing?

Accepted Answer

The 30-Second Answer: Baseline testing is the practice of establishing performance benchmarks for a system under known conditions, which serves as a reference point for detecting regressions. I run baseline tests after major releases or infrastructure changes to document expected performance, then compare future test results against this baseline to identify degradation or improvement.

Question 9

What is the test pyramid?

Accepted Answer

The 30-Second Answer: The test pyramid is a testing strategy framework that visualizes the ideal distribution of automated tests across different layers. It suggests having many fast, isolated unit tests at the base, fewer integration tests in the middle, and only a small number of slow, expensive end-to-end tests at the top. The 2-Minute Answer (If They Want More): The test pyramid is a metaphor that guides teams in creating a balanced and efficient automated test suite.

Question 10

What is the ice cream cone anti-pattern?

Accepted Answer

The 30-Second Answer: The ice cream cone anti-pattern is an inverted test pyramid where teams have many slow, expensive UI tests, few integration tests, and minimal unit tests. This leads to slow feedback loops, brittle test suites, difficult debugging, and high maintenance costsâ€”the opposite of what effective test automation should provide.

Performance and Load Testing(7 questions)

What is performance testing?

What is the difference between load testing, stress testing, and spike testing?

What are common performance testing tools (JMeter, Gatling, k6)?

How do you integrate performance tests into CI/CD?

What is baseline testing in performance testing?

How do you identify performance bottlenecks?

What metrics should you measure in performance testing?

Test Pyramid(12 questions)

What is the test pyramid?

Who introduced the test pyramid concept?

What are the layers of the traditional test pyramid?

Why should there be more unit tests than integration tests?

What is the ice cream cone anti-pattern?

What is the testing trophy and how does it differ from the pyramid?

How do you decide the right balance of tests at each level?

What is the cost and speed trade-off at different pyramid levels?

How does the test pyramid apply to microservices architecture?

What is the inverted test pyramid and why is it problematic?

How do you measure if your test distribution follows the pyramid?

What is the testing honeycomb?

Unit Testing(12 questions)

What is a unit test?

What is the definition of a "unit" in unit testing?

What are the characteristics of a good unit test?

What is the FIRST principle in unit testing?

What is the difference between solitary and sociable unit tests?

How do you achieve test isolation in unit tests?

What should and shouldn't be tested at the unit level?

How do you handle dependencies in unit tests?

What is the relationship between unit tests and code coverage?

How many assertions should a unit test have?

What is the AAA (Arrange-Act-Assert) pattern?

How do you name unit tests effectively?

Integration Testing(12 questions)

What is integration testing?

What is the difference between unit testing and integration testing?

What are the different approaches to integration testing (big bang, top-down, bottom-up, sandwich)?

What is contract testing?

How do you handle database dependencies in integration tests?

What is an in-memory database and when would you use it for testing?

How do you test API integrations?

What is the difference between integration tests and end-to-end tests?

How do you manage test data for integration tests?

What is component testing?

How do you handle external service dependencies in integration tests?

What are test containers and when would you use them?

End-to-End (E2E) Testing(12 questions)

What is end-to-end testing?

What are the benefits and drawbacks of E2E tests?

When should you write E2E tests vs other types of tests?

What are popular E2E testing tools (Cypress, Playwright, Selenium)?

How do you handle flaky E2E tests?

What is the Page Object Model pattern?

How do you manage test data in E2E tests?

What is visual regression testing?

How do you test user authentication flows in E2E tests?

What is the role of E2E tests in the test pyramid?

How do you parallelize E2E tests?

What is headless browser testing?

Mocking and Test Doubles(9 questions)

What is a test double?

What is the difference between mocks, stubs, fakes, and spies?

When should you use mocks vs real implementations?

What is over-mocking and why is it problematic?

How do you decide what to mock?

What is the mockist vs classicist debate in testing?

How do you mock external APIs?

What is contract testing and how does it reduce the need for mocking?

What are the dangers of mocking too much?

Test Coverage(8 questions)

What is code coverage?

What are the different types of coverage (line, branch, statement, function)?

What is a good code coverage percentage?

Why is 100% code coverage not always desirable?

What is mutation testing?

How do you identify untested code paths?

What is the difference between code coverage and test effectiveness?

How do you use coverage reports to improve tests?