Sanity testing, unit testing, and code review - with examples

In software development, sanity testing, unit testing, and code review each play crucial roles in ensuring the quality, reliability, and maintainability of the software. Here's a breakdown of their roles and the potential impact if these practices are not performed:

### Sanity Testing

- Purpose: Sanity testing is a subset of regression testing. It is used to verify that a particular function or bug fix works as intended and that no new issues have been introduced. It is typically focused and narrow in scope.

- When Performed: Sanity testing is usually performed after receiving a software build, and it is done before more extensive testing is conducted.

- Scope: It is generally a quick and cursory check to ensure the basic functionality of a particular module or feature.

- Example: If a bug is reported and fixed, sanity testing would involve checking the specific area of the application affected by the bug to ensure that the fix is successful and does not break other related functionality.

Impact of Not Performing Sanity Testing:

- Introduction of New Bugs: Without sanity testing, a new build might introduce unforeseen bugs in the application, which can go unnoticed until later stages of testing or production.

- Delayed Issue Detection: Problems that could have been caught early are discovered much later, leading to increased debugging time and higher costs for fixing issues.

- Wasted Effort: Testing broader aspects of the application without ensuring the basic functionality works can result in wasted time and resources.

Example Impact: Imagine a scenario where a bug was reported in the user login feature of an application. The bug is fixed and the new build is generated. Without sanity testing, the build is directly passed to the QA team for extensive testing. If the basic login functionality still has issues, all subsequent testing efforts on dependent features (e.g., user dashboard, profile management) will be futile because the QA team cannot even log in to test those features.

### Unit Testing

- Purpose: Unit testing involves testing individual components or units of code (such as functions, methods, or classes) in isolation to ensure they work correctly.

- When Performed: It is usually performed by developers during the development phase before the code is integrated into the larger codebase.

- Scope: Unit tests are focused on a small piece of functionality, often with mock objects or stubs used to isolate the unit from dependencies.

- Example: Testing a single function that calculates the sum of two numbers to ensure it returns the correct result for various input values.

Impact of Not Performing Unit Testing:

- Higher Defect Density: Without unit testing, individual components of the software are not validated in isolation, leading to a higher number of defects and integration issues.

- Difficult Debugging: When bugs arise, it becomes more challenging to pinpoint the source of the problem because individual units were not tested independently.

- Reduced Code Quality: The absence of unit tests often leads to lower confidence in the code’s functionality and can result in poor coding practices.

Example Impact: Consider a function that calculates discounts for an e-commerce application. If this function is not unit tested, any errors in its logic (e.g., incorrect percentage calculations, handling of edge cases) will propagate through the entire system. This can lead to incorrect discount applications during checkout, resulting in customer dissatisfaction and potential revenue loss.

### Code Review

- Purpose: Code review is the process of systematically examining the source code written by one or more developers to find and fix mistakes overlooked in the initial development phase, improve code quality, and share knowledge among the team.

- When Performed: Code review is performed before the code is merged into the main codebase. It can be done manually or with the help of automated tools.

- Scope: It involves a detailed inspection of the code, considering aspects such as correctness, readability, maintainability, performance, and adherence to coding standards.

- Example: Reviewing a pull request on a platform like GitHub, where a team member examines the code changes made by another developer, suggests improvements, and discusses potential issues.

Impact of Not Performing Code Reviews:

- Poor Code Quality: Without code reviews, code quality can degrade over time as developers may not adhere to best practices, leading to inconsistencies and technical debt.

- Increased Bugs: Unreviewed code is more likely to contain bugs that were overlooked by the original developer, leading to more frequent and severe issues in production.

- Knowledge Silos: The lack of code reviews can result in knowledge silos, where only the original author understands the code, making it difficult for other team members to maintain or extend it.

Example Impact: A developer writes a complex algorithm for a critical data processing feature. Without a code review, potential issues such as inefficient logic, poor error handling, or security vulnerabilities might not be identified. When this code goes into production, it could lead to performance bottlenecks or data corruption, which are costly and time-consuming to fix.

### Summary

- Sanity Testing: Quick validation to check if a specific functionality or bug fix works correctly after a build.

- Unit Testing: In-depth testing of individual components in isolation to ensure they function as expected.

- Code Review: Peer review process to improve code quality, catch errors, and ensure best practices are followed.

Impact of Not Performing These Practices:

- Sanity Testing: New builds may introduce undetected critical issues, causing delays and wasted testing efforts.

- Unit Testing: Higher defect rates and more difficult debugging due to untested individual components.

- Code Review: Degraded code quality, increased bugs, and knowledge silos within the development team.

Together, these practices help to create a robust development process that minimizes bugs, improves code quality, and facilitates collaboration among team members. Neglecting any of these can lead to significant issues that impact the overall success and maintainability of the software.