Vinyl: npm test on windows generates error

[BurtHarris]

I'm trying to build Vinyl from sources on a Windows machine. On Win10, npm test gives me this:

> vinyl@2.2.1 test C:\Code\sigil\vinyl
> nyc mocha --async-only

internal/modules/cjs/loader.js:638
    throw err;
    ^

Error: Cannot find module 'C:\Code\sigil\vinyl\node'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:636:15)
    at Function.Module._load (internal/modules/cjs/loader.js:562:25)
    at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)
----------|----------|----------|----------|----------|----------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
----------|----------|----------|----------|----------|----------------|
All files |  Unknown |  Unknown |  Unknown |  Unknown |                |
----------|----------|----------|----------|----------|----------------|
npm ERR! Test failed.  See above for more details.
PS C:\Code\sigil\vinyl>

I've tried on versions back to node@10.24.1, and npm@6.14.12, same error. The same repo checks out OK on Ubuntu. Any hints?