Local interceptors not working when using vi.mock in Vitest browser mode

[diego-aquino]

Prerequisites

• I confirm that none of the open issues match my problem
• I confirm that the documentation does not cover a solution to problem

Operating system

Ubuntu 24.04

Runtime

Node.js

Runtime version

22.13.1

Zimic version

0.12.3

Reproduction repository

https://github.com/diego-aquino/zimic-vi-mock-issue

Reproduction steps

1. pnpm install
2. pnpm test

Current behavior

The example test contains a simple fetch and a corresponding interceptor. However, the fetch fails with a network error. The problem appears to be related to using vi.mock, because commenting that line makes the test pass.

I suspect the cause are the changes introduced in the latest version of MSW. Vitest browser comes with an embedded MSW instance, likely used to mock imports when vi.mock is applied. However, Zimic's internal MSW version is not the latest because not all of our tests pass due to mswjs/msw#2146.

Expected behavior

Zimic should be able to intercept requests even if vi.mock is being used. We'll probably have to upgrade MSW to its latest version in #423. To fix the failing tests, we can use a tool such as patch-package to patch mswjs/msw#2146 with a workaround, while it is not fixed in MSW itself.

[diego-aquino]

Update: upgrading to [email protected] did not solve this issue. This does not appear to be a bug in Zimic.

Related issues:

• Browser: worker not mocking requests when vi.mock present mswjs/msw#2398
• The request from msw cannot be returned normally in browser mode when using vi.mock vitest-dev/vitest#7290

[diego-aquino]

Since remote interceptors do not use MSW, they are not affected by this issue. Changing from a local to a remote interceptor serves as a current workaround.