docs: document userland patterns for global assertionOptions in RuleT… by loveme-3000 · Pull Request #20986 · eslint/eslint

loveme-3000 · 2026-06-15T10:03:26Z

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I did not use AI to generate this PR.
(If the above is not checked) I have reviewed the AI-generated content before submitting.

What is the purpose of this pull request? (put an "X" next to an item)

[x] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Fixes #20613

What changes did you make? (Give an overview)

Added a new section "Enforcing assertionOptions Globally" to the RuleTester documentation in docs/src/integrate/nodejs-api.md.

Because assertionOptions is specified per run() call, there is currently no built-in way to enforce the same options across every call in a project. As discussed in #20613, the team decided to document userland patterns instead of adding a new API.

This PR documents two common approaches:

Subclassing RuleTester — Override run() to inject default assertionOptions, allowing per-call overrides via object spread.
Helper wrapper function — A standalone function that wraps ruleTester.run() with default assertionOptions, also supporting per-call overrides.

Both approaches were mentioned by @mdjermanovic in the issue discussion. The section is placed directly after the existing assertionOptions property documentation, under RuleTester#run().

Is there anything you'd like reviewers to focus on?

Whether documenting both approaches (subclass + helper function) is preferred, or if the team would like only one. @DMartens mentioned documenting "one way to do it," but @mdjermanovic referenced both patterns, so I included both for completeness.

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linux-foundation-easycla · 2026-06-15T10:03:34Z

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✅ login: loveme-3000 / name: loveme-3000 (19104b0)

DMartens · 2026-06-15T11:31:57Z

    - If `"error"`, each error object that specifies `messageId` must also specify `data` if the message referenced by `messageId` has [placeholders](../extend/custom-rules#use-message-placeholders).
    - If `"suggestion"`, each suggestion object that specifies `messageId` must also specify `data` if the message referenced by `messageId` has [placeholders](../extend/custom-rules#use-message-placeholders).

+#### Enforcing `assertionOptions` Globally


I think this should be a subsection under the existing "Customizing RuleTester".

DMartens · 2026-06-15T11:32:30Z

+}
+```
+
+Both approaches use object spread so that any `assertionOptions` provided on a specific `run()` call are merged on top of the defaults, allowing per-test-file overrides where needed.


This text is already present twice before in the examples, I do not think this should be repeated again.

DMartens · 2026-06-15T11:33:29Z

+```js
+const { RuleTester } = require("eslint");
+
+class StrictRuleTester extends RuleTester {


For both examples, it would make more sense to export the class or function.

DMartens · 2026-06-15T11:36:25Z

Please review our AI usage policy as the AI usage is not disclosed but this seems to be AI-generated (wording such as "userland" and repeating the same information multiple times).

- Move 'Enforcing assertionOptions Globally' under 'Customizing RuleTester' - Remove redundant object spread explanation paragraph - Export class/function in both examples

DMartens

Changes LGTM, thanks.

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docs: document userland patterns for global assertionOptions in RuleT…

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Change Request: Add the option to define assertionOptions globally #20613

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docs: address review feedback for assertionOptions section

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- Move 'Enforcing assertionOptions Globally' under 'Customizing RuleTester' - Remove redundant object spread explanation paragraph - Export class/function in both examples

loveme-3000 requested a review from DMartens June 18, 2026 17:19

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Comment thread docs/src/integrate/nodejs-api.md

docs: add subheading for describe/it customization in RuleTester

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