Use SimpleCov to monitor code coverage

[benthorner]

https://trello.com/c/epNWudCR/176-write-an-rfc-for-continuous-deployment-and-seek-review

We should always monitor the amount of code that is exercised when
we run our tests.

[kevindew]

It looks like this produces two different coverage reports (RSpec and Cucumer) do we not want a single one that combines them both? I've no idea if that's possible, mind.

[benthorner]

It does produce two reports, but they're distinct and automatically aggregated by SimpleCov:

{
  "RSpec": {
    "coverage": {
      "/govuk/transition/app/controllers/concerns/track_mappings_progress.rb": {
        "lines": [
          1,

...

    "timestamp": 1600778396
  },
  "Cucumber Features": {
    "coverage": {
      "/govuk/transition/app/controllers/concerns/track_mappings_progress.rb": {
        "lines": [
          1,

...

[kevindew]

Oh cool, so are we going to generate something with the file produced?

Thanks for explaining.

[benthorner]

Oh cool, so are we going to generate something with the file produced?

I'm not sure I follow. The combined coverage is visible in the coverage/index.html file, although it doesn't indicate what (kind of) test is covering the code. We get the web page report by default - perhaps that was an unknown for you?

[kevindew]

Oh cool, so are we going to generate something with the file produced?

I'm not sure I follow. The combined coverage is visible in the coverage/index.html file, although it doesn't indicate what (kind of) test is covering the code. We get the web page report by default - perhaps that was an unknown for you?

Sorry I wasn't very clear. I know that currently a file is created, however Jenkins doesn't do anything with it (as far as I'm aware) so I wondered if we'd be using it as part of a step or process.

[benthorner]

Discussed in person and all is well: the aggregated coverage is visible in a single file; the use of SimpleCov is primarily for some minimal visibility on a local machine, although we could monitor it more comprehensively in future.