Add Codecov (#1626)

Problem: We don't have a history of our code coverage and we want to see
how it changes over time and with every PR. We also want to have a badge
that shows the overall coverage.

Solution: Use Codecov to upload coverage and get diffs in every PR that
changes code. Also add a badge in the README to show the coverage.

.codecov.yml

@@ -0,0 +1,7 @@
+coverage:
+  status:
+    project:
+      default:
+        informational: true
+comment:
+  require_changes: true

.github/workflows/ci.yml

@@ -67,6 +67,11 @@ jobs:
       - name: Run Tests
         run: make unit-test
 
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@54bcd8715eee62d40e33596ef5e8f0f48dbbccab # v4.1.0
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+
       - name: Upload Coverage Report
         uses: actions/upload-artifact@5d5d22a31266ced268874388b861e4b58bb5c2f3 # v4.3.1
         with:

Makefile

@@ -140,10 +140,10 @@ lint: ## Run golangci-lint against code
 .PHONY: unit-test
 unit-test: ## Run unit tests for the go code
 	# We have to run the tests in the cmd package using `go test` because of a bug with the CLI library cobra. See https://github.com/spf13/cobra/issues/2104.
-	go test ./cmd/... -race -coverprofile cmd-cover.out
-	go run github.com/onsi/ginkgo/v2/ginkgo --randomize-all --randomize-suites --race --keep-going --fail-on-pending --trace --cover --coverprofile=cover.out -r internal
-	go tool cover -html=cover.out -o cover.html
-	go tool cover -html=cmd-cover.out -o cmd-cover.html
+	go test ./cmd/... -race -shuffle=on -coverprofile=cmd-coverage.out -covermode=atomic
+	go run github.com/onsi/ginkgo/v2/ginkgo --randomize-all --randomize-suites --race --keep-going --fail-on-pending --trace --covermode=atomic --coverprofile=coverage.out -r internal
+	go tool cover -html=coverage.out -o cover.html
+	go tool cover -html=cmd-coverage.out -o cmd-cover.html
 
 .PHONY: njs-unit-test
 njs-unit-test: ## Run unit tests for the njs httpmatches module

README.md

@@ -3,6 +3,7 @@
 [![Continuous Integration](https://github.com/nginxinc/nginx-gateway-fabric/actions/workflows/ci.yml/badge.svg)](https://github.com/nginxinc/nginx-gateway-fabric/actions/workflows/ci.yml)
 [![Conformance Testing](https://github.com/nginxinc/nginx-gateway-fabric/actions/workflows/conformance.yml/badge.svg)](https://github.com/nginxinc/nginx-gateway-fabric/actions/workflows/conformance.yml)
 [![Go Report Card](https://goreportcard.com/badge/github.com/nginxinc/nginx-gateway-fabric)](https://goreportcard.com/report/github.com/nginxinc/nginx-gateway-fabric)
+[![codecov](https://codecov.io/gh/nginxinc/nginx-gateway-fabric/graph/badge.svg?token=32ULC8F13Z)](https://codecov.io/gh/nginxinc/nginx-gateway-fabric)
 [![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/nginxinc/nginx-gateway-fabric?logo=github&sort=semver)](https://github.com/nginxinc/nginx-gateway-fabric/releases/latest)
 [![Slack](https://img.shields.io/badge/slack-%23nginx--gateway--fabric-green?logo=slack)](https://nginxcommunity.slack.com/channels/nginx-gateway-fabric)
 [![Project Status: Active – The project has reached a stable, usable state and is being actively developed.](https://www.repostatus.org/badges/latest/active.svg)](https://www.repostatus.org/#active)