🐛 BUG: fetchMock does not intercept fetch in a service binding worker

[thiskevinwang]

Which Cloudflare product(s) does this pertain to?

Workers Vitest Integration

What version(s) of the tool(s) are you using?

3.53.1 [wrangler], 0.2.6 [@cloudflare/vitest-pool-workers], 1.3.0 [vitest]

What version of Node are you using?

20.11.0

What operating system and version are you using?

Mac Ventura 13.5

Describe the Bug

Observed behavior

fetchMock does not appear to intercept fetch calls that are internal to another worker that is built and bound as a service binding.

Expected behavior

I'd expect fetchMock to intercept fetch calls in a service binding worker.

Steps to reproduce

1. Create worker A
2. Create worker B with entrypoint "Foo"
3. In worker B, call fetch(SOMETHING)
4. Create a test for worker A
5. Build worker B and set as service binding on worker A
6. From test for worker A, call fetchMock and intercept the previous SOMETHING
7. activate(), disableNetConnect(). Assert no pending mocks
8. Call code to test Worker A-to-B integration
9. Observe 1 outstanding interceptor
10. Observe a "Network connection lost" error from the fetch call.

See: https://github.com/thiskevinwang/workers-sdk-5789

Please provide a link to a minimal reproduction

https://github.com/thiskevinwang/workers-sdk-5789

Please provide any relevant error logs

No response

[thiskevinwang]

It looks like outboundService is one means to mock this class of fetches, but you're slightly bound to a static implementation, so it's not flexible.

• workers-sdk/fixtures/vitest-pool-workers-examples/multiple-workers/vitest.config.ts

  Line 87 in 9b4af8a

  outboundService: handleAuthServiceOutbound,

I also see a mutually exclusive fetchMock option, but it's unclear how you satisfy this field (assuming a vitest.config.ts file)

• https://github.com/cloudflare/workers-sdk/tree/main/packages/miniflare#interface-workeroptions

[thiskevinwang]

Update: added repro-repo https://github.com/thiskevinwang/workers-sdk-5789