feat(runtime-utils): add route middleware testing utility

[wattanx]

🔗 Linked issue

📚 Description

@nuxt/test-utils currently does not provide a utility for testing Nuxt route middleware in isolation.

To test middleware that uses Nuxt APIs such as navigateTo(), users currently need to either:

• perform an actual navigation in a Nuxt environment, or
• create their own utility that reproduces the Nuxt context required to execute middleware.

Using an actual navigation may also run unrelated global middleware and change the current route. This makes it difficult to test the behavior of a specific middleware in isolation.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@nuxt/test-utils@1799

npm i https://pkg.pr.new/vitest-environment-nuxt@1799

commit: ec2e7e4

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds runRouteMiddleware for direct execution of Nuxt route middleware without navigation. The utility resolves raw to and from locations, runs middleware within Nuxt context, manages middleware state, and restores that state after completion or failure. The runtime entry point exports the utility and its route types. Tests cover redirects, route normalization, abortNavigation(), and 403 abort handling.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to ec2e7

The new middleware testing utility can cause overlapping executions on the same Nuxt application to interfere with each other and leave stale execution state, potentially making concurrent middleware tests produce incorrect results. The risk is bounded to concurrent use of the utility and is mergeable with explicit owner awareness or follow-up.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a route middleware testing utility to runtime utilities.
Description check	✅ Passed	The description directly explains the need for isolated route middleware testing and matches the pull request changes.

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/middleware-utils

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

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Inline comments:
In `@src/runtime-utils/middleware.ts`:
- Around line 71-75: Update the middleware utility around the previous state
restoration to coordinate concurrent executions per nuxtApp, preventing an
earlier call from restoring obsolete _processingMiddleware or server-side
_middlewareTo values after another call has started. Track active executions or
serialize the utility, and add a concurrent-call test that asserts both
properties return to their original values once all promises settle.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Team

Run ID: 01471332-c440-48e6-ae92-928aed57445f

📥 Commits

Reviewing files that changed from the base of the PR and between c42f9a8 and ec2e7e4.

📒 Files selected for processing (3)

• examples/app-vitest-full/tests/nuxt/middleware.spec.ts
• src/runtime-utils/index.ts
• src/runtime-utils/middleware.ts

Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review.

[danielroe]

I like this! my only concern is whether we need to keep this in sync with the nuxt middleware implementation (but we have that problem elsewhere in test-utils, of course).

did you check if there were any way to share the real nuxt runtime code?