Testing the recommended TypeScript compiler option skipLibCheck.
Run yarn install after cloning the repo.
Then run yarn test to see the expected compile error.
After that run yarn test --skipLibCheck. The compile error is gone
The documentation says:
TypeScript will type check the code you specifically refer to in your app’s source code.
What it does not mention, but should not be surprising now that I think about
it, is that any library code that can not be compiled, but your app's source
code refers to, will be regarded as any. Even with noImplicitAny set to
true this does not yield a compile error.