DiffCov/README.md

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# Diff Cov

Simple CLI to print git and lcov diffs highlighted with test coverage status

![Example Output](assets/example-output.png)

</div>

## Installation

You can install the package with npm

```bash
npm i -g @adeattwood/diff-cov
```

You can run it directly with `npx`

```bash
npx @adeattwood/diff-cov
```

## Setup

For diff-cov to get the diff to your default branch, you must set up your
`origin/HEAD` ref. To test to see if you have this set up, run.

```bash
git rev-parse --abbrev-ref origin/HEAD
```

This should print out the origin ref to your default branch for this repo it
will print `origin/0.x`. If you get an unknown ref error, then you will need to
link `origin/HEAD` to your default branch with the below command.

```bash
git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/0.x
```

> **Note**:
> Make sure you change `0.x` for your default branch name typically `main` or
> `development`

## Usage

### Git diff

Before you run `diff-cov` you must run your test suite with coverage and output
a `lcov` coverage file. You must also have all your changes committed to ensure
it's included in the output.

Once you are ready to go, you can run `diff-cov` to print your diff highlighted
with coverage status. Any line not included in the coverage report will not be
highlighted and hit and missed lines will be colored green and red. You can use
the `--coverageFile` flag to specify the path to your coverage report if its
not in the default location of `./lcov.info`

```bash
diff-cov
diff-cov --coverageFile coverage/lcov.info
```

A report is printed at the bottom and colored with a threshold of `90%`
anything below this percentage coverage will be colored red.

### LCov diff

You can also print the coverage difference between to lcov.info files. To use
this run your tests with coverage for a first time. After its finished you can
copy your lcov.info file somewhere for later for example:

```shell
cp ./lcov.info /tmp/lcov.info
```

Then you can work on your test and run the tests once more with coverage to
generate you a new `lcov.info` file. Then you can print the difference in
coverage between the two files with:

```shell
diff-cov --compare /tmp/lcov.info
```

This can come in handy when you need to find out what a test is testing. You
can create your base coverage file, comment out a test, run the tests again and
diff the results.