Identify what test covers what lines

[gaborbernat]

Currently, there's no way to find out what tests are covering a given line, it would be nice to have this feature. In the Python language this is named dynamic contexts, see https://coverage.readthedocs.io/en/7.4.3/contexts.html#dynamic-contexts.

[ericmorand]

That would require a dedicated runtime to support this. c8 is just running whatever is passed as argument. There is no way for it to know how a line was hit if this information is not given by the runtime itself (node, or v8 more specifically).

Also, even if it was possible, how would it be able to detect the test? Basically: what is a test?

• foo.mjs

export const foo = () => 5;

• index.mjs

import {foo} from "./foo";

foo();

c8 node index.mjs

foo.mjs is fully covered here. But what would be the test?