Error running tests the first time only

[drrb]

Hello, I'm using Snowpack 3.1.2. The first time I run npm run test after doing npm install (I do this in my CI build), I get an error. Subsequent runs pass. The problem goes away if I downgrade to Snowpack 3.0.13. Unfortunately I can't share my sources, but I generated my project with npx create-snowpack-app myapp --template @snowpack/app-template-react-typescript. Error is:

$ npm run test

> @ test /home/me/code/myapp
> web-test-runner "src/**/*.test.tsx"

[snowpack] starting server...
[02:17:20] [snowpack] Welcome to Snowpack! Because this is your first time running
this project (mode: test), Snowpack needs to prepare your dependencies. This is a one-time step
and the results will be cached for the lifetime of your project. Please wait...
[02:17:20] [snowpack] + @testing-library/react@11.2.5
... more dependency output
[02:17:43] [snowpack] Ready!
[02:17:43] [snowpack] Server started in 62ms.
[02:17:43] [snowpack] Local: http://localhost:8080
[02:17:43] [snowpack] Network: http://10.36.138.156:8080
[02:17:43] [snowpack] watching for file changes... 
Chrome: |██████████████████████████████| 0/1 test files | 0 passed, 0 failed
Running tests...
Running 1 test files...
[02:17:43] [@snowpack/plugin-typescript] 1:16:43 AM - Starting compilation in watch mode...
[02:17:44] [snowpack] + @restart/hooks/useMounted@0.3.26
[02:17:45] [snowpack] └── react@17.0.1 (dedupe)
src/App.test.tsx:
 🚧 Browser logs:
      TypeError: Failed to fetch dynamically imported module: http://localhost:8000/dist/App.test.js
 🚧 404 network requests:
    - _snowpack/pkg/@restart/hooks.v0.3.26/common/useMounted-a52d50d8.js
 ❌ Could not import your test module. Check the browser logs or open the browser in debug mode for more information. 
Chrome: |██████████████████████████████| 1/1 test files | 0 passed, 0 failed
Error while running tests.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @ test: `web-test-runner "src/**/*.test.tsx"`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the @ test script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR!     /home/me/.npm/_logs/2021-03-30T01_16_45_579Z-debug.log