Smoke testing and sanity testing in Testing Fundamentals - Full Explanation

Introduction

Imagine you just fixed a few parts of a big machine. Before using it fully, you want to quickly check if the main parts still work and if the recent fixes did not break anything. This is where smoke testing and sanity testing help in software testing.

Explanation

Smoke Testing

Smoke testing is a quick check to see if the basic and important functions of a software application work after a new build or update. It covers the main features to ensure the software is stable enough for further detailed testing. If smoke testing fails, the software is sent back for fixes before any deeper testing happens.

Smoke testing quickly verifies the core functions of software to decide if it is ready for detailed testing.

Sanity Testing

Sanity testing is a focused check done after receiving a software build with minor changes or bug fixes. It ensures that the specific parts fixed or changed work correctly and that no new problems appeared in those areas. Sanity testing is narrower than smoke testing and is done to confirm the correctness of particular functionalities.

Sanity testing confirms that recent changes or fixes in the software work as expected without new issues.

Real World Analogy

Imagine you have a car that just had some repairs. Before driving it on a long trip, you first check if the engine starts and the brakes work (smoke testing). Then, after fixing a small issue with the headlights, you check only the headlights to make sure they work properly (sanity testing).

Smoke Testing → Checking if the car's engine starts and brakes work before a trip

Sanity Testing → Checking if the headlights work properly after a small repair

Diagram

Diagram

┌─────────────────────┐
│    Software Build    │
└─────────┬───────────┘
          │
          ▼
  ┌─────────────────┐       ┌─────────────────┐
  │   Smoke Testing │──────▶│ Pass?           │
  └─────────────────┘       └───────┬─────────┘
          │                          │
          │Yes                       │No
          ▼                          ▼
  ┌─────────────────┐       ┌─────────────────┐
  │  Sanity Testing │       │ Return for Fixes│
  └─────────────────┘       └─────────────────┘

This diagram shows the flow from a software build through smoke testing, deciding if it passes, then moving to sanity testing or returning for fixes.

Key Facts

Smoke Testing → A quick test of core software functions to check stability after a new build.

Sanity Testing → A focused test on specific changes or fixes to verify correctness.

Purpose of Smoke Testing → To decide if software is stable enough for detailed testing.

Purpose of Sanity Testing → To confirm recent changes work and did not break related parts.

Common Confusions

Smoke testing and sanity testing are the same.

Smoke testing and sanity testing are the same. Smoke testing checks the whole software's basic functions quickly, while sanity testing focuses only on specific changes or fixes.

Sanity testing is done before smoke testing.

Sanity testing is done before smoke testing. Smoke testing is done first to check overall stability; sanity testing follows to verify particular fixes.

Summary

Smoke testing quickly checks if the main features of software work after a new build.

Sanity testing verifies that recent fixes or changes function correctly without new issues.

Smoke testing covers broad basic checks; sanity testing is narrow and focused on specific areas.

Practice

1. What is the main purpose of smoke testing in software testing?

easy

A. To perform security testing on the application

B. To quickly check if the main features of a new build work

C. To verify the user interface design

D. To test detailed functionality of all features

Solution

1. Step 1: Understand smoke testing purpose

   Smoke testing is done to quickly verify that the main features of a new software build are working and the build is stable enough for further testing.

2. Step 2: Compare options with smoke testing definition

   To quickly check if the main features of a new build work matches this purpose exactly, while others describe different testing types.

3. Final Answer:

   To quickly check if the main features of a new build work -> Option B

4. Quick Check:

   Smoke testing = Quick main feature check [OK]

Hint: Smoke test = quick main feature check after build [OK]

Common Mistakes:

• Confusing smoke testing with detailed testing
• Thinking smoke testing checks UI design
• Mixing smoke testing with security testing

2. Which of the following is the correct description of sanity testing?

easy

A. Checking specific functionality after small changes or bug fixes

B. Testing all features in detail after a major release

C. Performing load testing to check performance

D. Running automated tests for regression

Solution

1. Step 1: Define sanity testing

   Sanity testing is a quick check of specific functionality or bug fixes after small changes to ensure they work as expected.

2. Step 2: Match options to sanity testing

   Checking specific functionality after small changes or bug fixes correctly describes this focused testing, while others describe different testing types.

3. Final Answer:

   Checking specific functionality after small changes or bug fixes -> Option A

4. Quick Check:

   Sanity testing = Focused check after small changes [OK]

Hint: Sanity test = check specific fixes after small changes [OK]

Common Mistakes:

• Confusing sanity testing with full regression testing
• Thinking sanity testing covers all features
• Mixing sanity testing with performance testing

3. Consider this scenario: A new build is deployed with multiple new features and bug fixes. Which testing should be done first to decide if detailed testing can proceed?

medium

A. Sanity testing on the fixed bugs only

B. Full regression testing on all features

C. Smoke testing on main features of the build

D. Performance testing under load

Solution

1. Step 1: Identify testing purpose after new build

   After a new build with many changes, smoke testing is done first to quickly check main features and decide if the build is stable for further testing.

2. Step 2: Evaluate options for initial testing

   Smoke testing on main features of the build matches this initial check. Sanity testing (Sanity testing on the fixed bugs only) is for small changes, not full builds. Full regression (Full regression testing on all features) and performance (Performance testing under load) come later.

3. Final Answer:

   Smoke testing on main features of the build -> Option C

4. Quick Check:

   New build? Start with smoke testing [OK]

Hint: New build? Start with smoke testing main features [OK]

Common Mistakes:

• Starting with sanity testing on big builds
• Skipping smoke testing and doing full regression immediately
• Confusing performance testing as first step

4. A tester runs sanity testing after a small bug fix but finds unrelated features failing. What is the likely cause?

medium

A. Sanity testing scope was too narrow, missing regression tests

B. Smoke testing was done incorrectly

C. The bug fix introduced new unrelated bugs

D. Performance testing was skipped

Solution

1. Step 1: Understand sanity testing scope

   Sanity testing focuses on verifying specific fixes or features, not the entire application.

2. Step 2: Analyze failure of unrelated features

   If unrelated features fail, it means sanity testing missed broader checks. Full regression testing is needed to catch such issues.

3. Final Answer:

   Sanity testing scope was too narrow, missing regression tests -> Option A

4. Quick Check:

   Unrelated failures after sanity test? Need regression [OK]

Hint: Sanity test checks fixes only; unrelated fails need regression [OK]

Common Mistakes:

• Blaming smoke testing for unrelated failures
• Assuming bug fix always causes unrelated failures
• Ignoring need for regression testing

5. A software team wants to improve testing efficiency after frequent small updates. Which approach best combines smoke and sanity testing?

hard

A. Perform performance testing before smoke or sanity testing

B. Skip smoke testing and run full regression after each update

C. Only run sanity testing on all features after every update

D. Run smoke testing on main features after every build, then sanity testing on specific fixes

Solution

1. Step 1: Understand testing goals for frequent small updates

   To improve efficiency, quick checks are needed to catch major issues early, then focused checks on fixes.

2. Step 2: Evaluate combined approach of smoke and sanity testing

   Running smoke testing on main features ensures build stability, followed by sanity testing on specific fixes ensures correctness of changes.

3. Step 3: Eliminate other options

   Skipping smoke testing or running full regression every time is inefficient. Performance testing is unrelated to this goal.

4. Final Answer:

   Run smoke testing on main features after every build, then sanity testing on specific fixes -> Option D

5. Quick Check:

   Smoke then sanity for efficient small update testing [OK]

Hint: Smoke test main features, then sanity test fixes for efficiency [OK]

Common Mistakes:

• Skipping smoke testing for faster results
• Running full regression after every small update
• Confusing performance testing with smoke/sanity