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Linting in playwright projects

Linting is a crucial part of maintaining code quality in any software project. It involves analyzing code to flag programming errors, bugs, stylistic errors, and suspicious constructs. By integrating linting into your development workflow, you can ensure that your code adheres to defined standards and best practices.

Benefits of Linting

Linting offers several benefits in the context of Playwright projects:

  1. Early Detection of Test Issues: Linting helps identify common mistakes and anti-patterns in your Playwright test code, such as improper use of assertions or asynchronous operations, before they cause test failures.

  2. Consistent Test Code Style: By enforcing a uniform coding style, linting ensures that all Playwright tests are easy to read, review, and maintain, regardless of who wrote them.

  3. Improved Test Reliability: Linting can catch flaky test patterns and encourage best practices, leading to more stable and reliable automated tests.

  4. Efficiency in Code Reviews: Linting reduces the cognitive load during code reviews by ensuring that stylistic and common coding issues are addressed, allowing reviewers to focus on the logic and functionality of the tests.

There are several popular linting tools available for different programming languages. Here are some widely used ones:

  • ESLint: A widely used linting tool for JavaScript and TypeScript that helps identify and fix problems in your code.
  • Pylint: A popular linting tool for Python that checks for errors, enforces coding standards, and suggests improvements.
  • Rubocop: A Ruby static code analyzer and formatter that helps enforce the Ruby style guide.
  • StyleCop Analyzers: A popular linting tool for C# and .NET projects. StyleCop analyzes C# source code to enforce a set of style and consistency rules, helping maintain code quality and readability in .NET-based Playwright test projects.
  • Roslyn Analyzers: A collection of code analysis tools built on the .NET Compiler Platform ("Roslyn"). These analyzers can enforce coding standards, detect code smells, and provide suggestions for improvement in C# and VB.NET codebases.

Linting in Playwright Projects

In Playwright projects, linting can be integrated to ensure that your test code adheres to best practices and coding standards. After all, test code is still application code, and maintaining its quality is just as important as the application code itself.

Depending on the programming language used in your tests, you can choose an appropriate linting tool. In this example, we will focus on using ESLint for JavaScript and TypeScript Playwright projects.

Step-by-Step: Setting Up ESLint v9+ in a Playwright TypeScript Project

Follow these steps to set up ESLint (version 9 or later) for a Playwright project using TypeScript:

  1. Install ESLint and Required Plugins Open your terminal in the root of your project and run:
npm install --save-dev eslint@^9 @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint-plugin-playwright
  1. Create ESLint Flat Config ESLint v9+ uses the new flat config format. In your project root, create a file named eslint.config.js with the following content:
// eslint.config.js
import js from '@eslint/js';
import tseslint from '@typescript-eslint/eslint-plugin';
import tsparser from '@typescript-eslint/parser';
import playwright from 'eslint-plugin-playwright';

export default [
  js.configs.recommended,
  {
    files: ['**/*.ts', '**/*.tsx'],
    languageOptions: {
      parser: tsparser,
      parserOptions: {
        project: './tsconfig.json',
      },
    },
    plugins: {
      '@typescript-eslint': tseslint,
      playwright,
    },
    rules: {
      ...tseslint.configs.recommended.rules,
      ...playwright.configs.recommended.rules,
    },
  },
];

Note: If you use CommonJS, you can use require and module.exports instead of import/export default.

  1. Add Lint Scripts (Optional) Add a script to your package.json for convenience:
"scripts": {
  "lint": "eslint . --ext .ts,.tsx"
}
  1. Run ESLint Lint your codebase with: 
    npm run lint

For more information on adding rules specific to Playwright, refer to the GitHub repository's README of the Playwright ESLint plugin.

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