README

For: istanbuljs/nyc#570

Problem: Version 10.3.2 of nyc considers typescript interface files when calculating coverage.

This repo demonstrates the difference in how nyc treats typescript interfaces between versions 10.1.2 and 10.3.2.

10.1.2

• cd 10.1.2
• npm install
• npm run cover
• See File [/Users/.../nyc-typescript-interface-cover/10.1.2/src/Fish.ts] ignored, nothing could be mapped warning
• See 100% coverage

10.3.2

• cd 10.3.2
• npm install
• npm run cover
• Do NOT see File [/Users/.../nyc-typescript-interface-cover/10.1.2/src/Fish.ts] ignored, nothing could be mapped warning
• See less than 100% coverage

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I think there is "nothing to test" for an interface file, so even though the warnings in version 10.1.2 were annoying, it made sense that the interface files were ignored.

Now with version 10.3.2, the warnings are gone because the interface files are counted towards lines covered. This is incorrect in my opinion, so the point of opening this issue is to determine if this change was intentional.

---

Solved:

See run_on_compiled branch for solution that works for both versions (run nyc on compiled javascript instead of using ts-node).