What do the delta figures mean?

[JoseAlcerreca]

Thanks for this action, we're trying it out in android/nowinandroid.

What do the the deltas mean? E.g. -0.13%? It looks like a comparison with the base branch, which would be nice, but I think that's impossible.

I've spent 10 minutes trying to fint the answer, so I think the README should explain it.

[sheepkacper]

Here is the part of the code that calculates it:

and this is the actual method:

[thsaravana]

Yes, I will add this to the README.md

You are right, the delta is not calculated based on the base branch (which is sadly not possible). Instead, it does the next closest thing.

Let's say you add or modify 10 lines of code in a file. If you have also added unit tests, that covers 8 lines out of those 10 lines, i.e, 2 lines are not covered by any tests, then the delta would be -20%. So the delta essentially gives you visibility on how many newly added/modified lines are not covered by unit tests.

This does have it's own limitations. For instance, the delta can never be positive, i.e, if you raise a PR with more Unit Tests adding coverage to exiting code (non modified one), those won't be considered in calculating the delta, as there is no way to figure that out.