Testing & Code Quality

ESLint & typescript-eslint

ESLint catches code-quality and correctness issues through configurable rules. typescript-eslint lets ESLint parse TypeScript and run TypeScript-aware rules that use compiler type information.

Linting is automated code review for repeatable concerns
Typed rules are more powerful and more expensive
Rule severity should reflect real risk
Flat config is the modern ESLint configuration direction
Linting should support project style, not become the project

Typed linting shape

export default [
  {
    files: ["**/*.ts", "**/*.tsx"],
    languageOptions: {
      parserOptions: {
        projectService: true,
      },
    },
    rules: {
      "@typescript-eslint/no-floating-promises": "error",
      "@typescript-eslint/no-explicit-any": "warn",
    },
  },
]

Typed linting can catch issues the TypeScript compiler alone may not report.

Lint rule categories
Category	Example
Correctness	no-floating-promises
Safety	no-explicit-any / no-unsafe-assignment
Maintainability	no-unused-vars, complexity
Style consistency	naming conventions
Framework rules	React hooks, testing-library rules