docs: added TESTING_DOCS for better understanding of testing (#19249)

CONTRIBUTING.md

@@ -47,6 +47,7 @@ Something that will increase the chance that your pull request is accepted:
 - For a major fix/feature make sure your PR has an issue and if it doesn't, please create one. This would help discussion with the community, and polishing ideas in case of a new feature.
 - Make sure your PR's description contains GitHub's special keyword references that automatically close the related issue when the PR is merged. ([More info](https://github.com/blog/1506-closing-issues-via-pull-requests))
 - When you have a lot of commits in your PR, it's good practice to squash all your commits in one single commit. ([Learn how to squash here](https://davidwalsh.name/squash-commits-git))
+- For a better understanding of the folder structure and testing procedures, refer to the [Testing Documentation](./TESTING_DOCS.md).
 
 ## Documentation
 

TESTING_DOCS.md

@@ -0,0 +1,102 @@
+# Webpack Test Suite Structure
+
+This document explains the structure of the `test/` directory in the Webpack project using Jest. The directory is organized into multiple folders and files, each serving a specific purpose in testing various aspects of Webpack’s functionality.
+
+## Folder and File Breakdown
+
+### 1. `__snapshots__/`
+
+- **Purpose**: Stores Jest snapshot files for comparing output consistency over time.
+- **Usage**: Used for testing UI components, serialized data, or expected module outputs.
+
+### 2. `benchmarkCases/`
+
+- **Purpose**: Contains test cases for benchmarking Webpack's performance.
+- **Usage**: Measures build times, memory usage, and optimization impact.
+
+### 3. `cases/`
+
+- **Purpose**: General test cases covering core functionalities.
+- **Usage**: Includes unit and integration tests for various modules and features.
+
+### 4. `configCases/`
+
+- **Purpose**: Tests related to Webpack configurations.
+- **Usage**: Ensures that Webpack’s configuration (e.g., loaders, plugins) functions correctly.
+
+### 5. `fixtures/`
+
+- **Purpose**: Stores sample/mock data used in tests.
+- **Usage**: Helps in creating consistent test cases with predefined inputs.
+
+### 6. `helpers/`
+
+- **Purpose**: Utility functions and scripts to assist in testing.
+- **Usage**: Provides reusable functions for mock data generation, cleanup, and assertions.
+
+### 7. `hotCases/`
+
+- **Purpose**: Focuses on Webpack’s Hot Module Replacement (HMR) functionality.
+- **Usage**: Ensures live reloading and hot updates work correctly.
+
+### 8. `hotPlayground/`
+
+- **Purpose**: An experimental space for testing HMR features.
+- **Usage**: Allows exploration of new HMR implementations.
+
+### 9. `memoryLimitCases/json`
+
+- **Purpose**: Contains test cases related to memory limits.
+- **Usage**: Ensures Webpack doesn’t exceed memory constraints.
+
+### 10. `statsCases/`
+
+- **Purpose**: Tests focused on Webpack’s statistical outputs.
+- **Usage**: Verifies correct bundle sizes, dependencies, and optimizations.
+
+### 11. `typesCases/`
+
+- **Purpose**: Type-checking tests, likely for TypeScript integration.
+- **Usage**: Ensures proper type definitions and compliance.
+
+### 12. `watchCases/`
+
+- **Purpose**: Tests for Webpack’s watch mode functionality.
+- **Usage**: Ensures file changes trigger correct rebuild behavior.
+
+### 13. `*.unittest.js`
+
+- **Purpose**: Contains unit tests for various functionalities.
+- **Usage**: Ensures individual modules and functions work as expected.
+
+### 14. `BannerPlugin.test.js`
+
+- **Purpose**: Tests Webpack’s `BannerPlugin` functionality.
+- **Usage**: Ensures that the plugin correctly adds banners to the bundled files.
+
+## Testing Framework
+
+- **Jest** is used for running tests.
+- Snapshots help maintain consistency in output.
+- Unit tests verify individual module functionality.
+- Integration tests ensure multiple components work together.
+
+## How to Run Tests
+
+To execute all tests, use the following command:
+
+```sh
+yarn test
+```
+
+For running specific tests:
+
+```sh
+jest cases/userLogic.test.js
+```
+
+## Contribution Guide
+
+- Add new test cases in the appropriate folder.
+- Use Jest assertions and mocks for consistency.
+- Run `yarn test` before pushing changes to validate functionality.