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#7795 Issue with testing workers using SELF

Recommendation:CLOSE
Difficulty:n/a
Reasoning:

User configuration error, not bug. Reporter using literal object config instead of defineWorkersConfig(). Aug 2025 comment identified fix. Reproduction repo shows same incorrect pattern.

Suggested Action:

Close as configuration error with explanation of correct pattern

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Analysis Report

Issue Review: cloudflare/workers-sdk#7795

Summary

SELF import from cloudflare:test fails with "Failed to load url cloudflare:test" error.

Findings

  • Created: 2025-01-16
  • Updated: 2025-10-30
  • Version: wrangler 3.101.0, @cloudflare/vitest-pool-workers 0.6.0 -> 4.60.0 / 0.12.6
  • Component: vitest-pool-workers
  • Labels: bug, vitest
  • Comments: 4

Key Evidence

  • Reproduction repo provided: https://github.com/valeriydev/self-issue
  • Maintainer @penalosa requested reproduction (Jan 2025)
  • User provided reproduction repo (Jan 2025)
  • Another user linked to potentially related #6214 (Feb 2025)
  • CRITICAL: @njdancer (Aug 2025) identified root cause as USER ERROR
    • Reporter was defining vitest config as literal object instead of using defineWorkersConfig()
    • The linked reproduction repo also contains this incorrect pattern
    • Using defineWorkersConfig() function correctly resolves the issue

Recommendation

Status: CLOSE

Reasoning: This is not a bug but a user configuration error. The reporter and reproduction repo both use an incorrect pattern (defining vitest config as a literal object) instead of the correct pattern (using defineWorkersConfig() from @cloudflare/vitest-pool-workers/config). @njdancer confirmed that using the correct configuration pattern resolves the issue.

Action: Close as configuration error. The documentation at https://developers.cloudflare.com/workers/testing/vitest-integration/configuration/ clearly shows the correct usage.

Suggested Comment

Closing this issue as it appears to be a configuration error rather than a bug.

As @njdancer identified, the issue is that the vitest config is defined as a literal object instead of using the defineWorkersConfig() function:

Incorrect:

export default {
  test: { poolOptions: { workers: { ... } } }
};

Correct:

import { defineWorkersConfig } from "@cloudflare/vitest-pool-workers/config";
export default defineWorkersConfig({
  test: { poolOptions: { workers: { ... } } }
});

The defineWorkersConfig() function is required to properly set up the cloudflare:test module resolution. See the configuration documentation.

If you're still experiencing issues after using the correct configuration pattern, please open a new issue with an updated reproduction.

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