Add SimpleCov to report code coverage

Author: Ben Thorner

.gitignore

@@ -18,3 +18,4 @@
 /public/government-frontend
 /test/wraith/wip*
 shots/*
+/coverage

Gemfile

@@ -38,6 +38,7 @@ group :test do
   gem "faker"
   gem "minitest-reporters"
   gem "mocha"
+  gem "simplecov"
   gem "webdrivers"
   gem "webmock", require: false
 end

Gemfile.lock

@@ -92,6 +92,7 @@ GEM
     crass (1.0.6)
     dalli (2.7.10)
     debug_inspector (0.0.3)
+    docile (1.3.2)
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
     erubi (1.9.0)
@@ -308,6 +309,10 @@ GEM
       rubyzip (>= 1.2.2)
     sentry-raven (3.0.4)
       faraday (>= 1.0)
+    simplecov (0.19.0)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+    simplecov-html (0.12.3)
     slimmer (15.1.1)
       activesupport
       json
@@ -394,6 +399,7 @@ DEPENDENCIES
   rubocop-govuk
   sass-rails
   scss_lint-govuk
+  simplecov
   slimmer
   uglifier
   webdrivers

test/test_helper.rb

@@ -2,6 +2,10 @@
 ENV["GOVUK_APP_DOMAIN"] = "test.gov.uk"
 ENV["GOVUK_ASSET_ROOT"] = "http://static.test.gov.uk"
 
+# Must go at top of file
+require "simplecov"
+SimpleCov.start
+
 require File.expand_path("../config/environment", __dir__)
 require "rails/test_help"
 require "capybara/rails"