@typescript-eslint/rule-tester: Support for custom cwd in test configuration

[conarti]

Description

@typescript-eslint/rule-tester does not provide a way to set custom cwd for the linter used in tests. This makes it impossible to test rules that depend on path resolution with custom working directories or alias imports (like @/).

Expected Behavior

The RuleTesterConfig should support a cwd option that would be passed to the Linter constructor, similar to how it works in ESLint core.

const ruleTester = new RuleTester({
  languageOptions: { /* ... */ },
  cwd: '/custom/working/directory',
});

Current Behavior

• There is no cwd option in RuleTesterConfig
• The linter is created internally with a computed basePath based on tsconfigRootDir and filename
• Custom working directories cannot be set for test scenarios

Use Case

We have ESLint rules that need to:

1. Resolve alias imports (e.g., @/ mapped to src/)
2. Work with specific project structures that depend on context.getCwd()
3. Test behavior with different working directories

Workaround

Currently, we have to skip tests that require custom cwd:

describe.skip('tests with custom cwd', () => {
  // Tests that need custom cwd
});

Implementation Suggestion

The Linter is created in #getLinterForFilename method. The cwd could be:

1. Added to RuleTesterConfig interface
2. Passed to the Linter constructor instead of the computed basePath when explicitly set

Environment

• @typescript-eslint/rule-tester: ^8.45.0
• eslint: ^9.11.1
• Node.js: v22.18.0

Would appreciate any guidance or if there's an existing way to achieve this that I'm missing!

[kirkwaiblinger]

Closely related to #11274

[JoshuaKGoldberg]

@typescript-eslint/rule-tester is based off of the core ESLint RuleTester - which does not have a cwd. We'd normally suggest filing the issue to ESLint itself.

For reference, the tseslint class defaults to the tsconfigRootDir or process.cwd():

typescript-eslint/packages/rule-tester/src/RuleTester.ts

Lines 202 to 203 in c7119b5

	let basePath: string | undefined =
	this.#testerConfig.languageOptions.parserOptions?.tsconfigRootDir;

typescript-eslint/packages/rule-tester/src/RuleTester.ts

Line 216 in c7119b5

path.resolve(basePath ?? process.cwd(), filename),

typescript-eslint/packages/rule-tester/src/RuleTester.ts

Lines 222 to 225 in c7119b5

	linterForBasePath = new Linter({
	configType: 'flat',
	cwd: basePath,
	});

@conarti I would suggest posting a reproduction (https://antfu.me/posts/why-reproductions-are-required)? If tsconfigRootDir isn't enough for you it'd be good to know why.

---

@typescript-eslint/triage-team I think this is blocked on discussing adding cwd to ESLint core. What do you think?

[JoshuaKGoldberg]

The 👍 and another look-through make me more confident here that:

• Most of the issues around the default / implicit cwd with RuleTester right now are likely due to Bug: context.cwd is incorrect set as / when absolute path is used as filename in rule tester #11274
• Otherwise adding an explicit cwd option to RuleTester would need to be proposed to ESLint first: https://github.com/eslint/eslint/issues

Closing this issue out in the meantime. If and when ESLint core adds a cwd to its RuleTester, we can re-open or file a new issue to add a corresponding option to @typescript-eslint/rule-tester's. Thanks for filing!