Update Code Coverage documentation

README.md

@@ -127,6 +127,8 @@ Each test suite generates a report in CircleCI. For a complete overview of testi
 
 Our code coverage is generated during the runtime of our unit, e2e, and visual tests. The combination of those reports is published to [codecov.io](https://app.codecov.io/gh/nasa/openmct/)
 
+For more on the specifics of our code coverage setup, [see](TESTING.md#code-coverage)
+
 # Glossary
 
 Certain terms are used throughout Open MCT with consistent meanings

TESTING.md

@@ -37,14 +37,42 @@ Documentation located [here](./e2e/README.md)
 
 ## Code Coverage
 
-* 100% statement coverage is achievable and desirable.
+It's up to the individual developer as to whether they want to add line coverage in the form of a unit test or e2e test.
 
-Codecov.io will combine each of the above commands with [Codecov.io Flags](https://docs.codecov.com/docs/flags). Effectively, this allows us to combine multiple reports which are run at various stages of our CI Pipeline or run as part of a parallel process.
+Line Code Coverage is generated by our unit tests and e2e tests, then combined by ([Codecov.io Flags](https://docs.codecov.com/docs/flags)), and finally reported in Github PRs by Codecov.io's PR Bot. This workflow gives a comprehensive (if flawed) view of line coverage.
 
-This e2e coverage is combined with our unit test report to give a comprehensive (if flawed) view of line coverage.
+### Karma-istanbul
+
+Line coverage is generated by our `karma-coverage-istanbul-reporter` package as defined in our `karma.conf.js` file:
+
+```js
+    coverageIstanbulReporter: {
+      fixWebpackSourcePaths: true,
+      skipFilesWithNoCoverage: true,
+      dir: 'coverage/unit', //Sets coverage file to be consumed by codecov.io
+      reports: ['lcovonly']
+    },
+```
+
+Once the file is generated, it can be published to codecov with
+
+```json
+    "cov:unit:publish": "codecov --disable=gcov -f ./coverage/unit/lcov.info -F unit",
+```
+
+### e2e
+
+The e2e line coverage is a bit more complex than the karma implementation. 
+
+This is the general sequence of events:
+1. Each e2e suite will start the webpack.coverage.js config with the `npm run start:coverage` command which configures webpack with the `babel-plugin-istanbul` babel-loader to generate code coverage during e2e test execution.
+1. Each e2e shard will generate only a piece of the larger coverage suite. This is converted with `nyc` with the `npm run cov:e2e:report` script
+1.a Most of the tests are run in the '@stable' configuration a focus on chrome/ubuntu at a single resolution. This coverage is published to codecov with `npm run cov:e2e:stable:publish`.
+1.b Some of our coverage only appears when run against `@unstable` tests, persistent datastore (couchdb), non-ubuntu machines, and non-chrome browsers with the `npm run cov:e2e:full:publish` flag. Since this happens about once a day, we have leveraged codecov.io's carryforward flag to report on lines covered outside of each commit on an individual PR.
 
 ### Limitations in our code coverage reporting
 
-Our code coverage implementation has two known limitations:
-- [Variability and accuracy](https://github.com/nasa/openmct/issues/5811)
-- [Vue instrumentation](https://github.com/nasa/openmct/issues/4973)
+Our code coverage implementation has some known limitations:
+- [Variability](https://github.com/nasa/openmct/issues/5811)
+- [Accuracy](https://github.com/nasa/openmct/issues/7015)
+- [Vue instrumentation gaps](https://github.com/nasa/openmct/issues/4973)