chore: add test coverage in PRs as comment (#884)

* generate test coverage in CI pipeline
* add pipeline which adds comments in PR with test coverage

.github/workflows/ci.yaml

@@ -1,9 +1,16 @@
 name: CI Workflow
 
-on: [pull_request, workflow_dispatch]
+on:
+  pull_request:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
 
 env:
   GO_VERSION: "1.24"
+  CODE_COVERAGE_FILE_NAME: "coverage.out" # must be the same as in Makefile
+  CODE_COVERAGE_ARTIFACT_NAME: "code-coverage"
 
 jobs:
   main:
@@ -33,8 +40,17 @@ jobs:
       - name: Test
         run: make test
 
+
+      - name: Archive code coverage results
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ env.CODE_COVERAGE_ARTIFACT_NAME }}
+          path: "stackit/${{ env.CODE_COVERAGE_FILE_NAME }}"
+
+
   config:
     name: Check GoReleaser config
+    if: github.event_name == 'pull_request'
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -44,3 +60,20 @@ jobs:
         uses: goreleaser/goreleaser-action@v6
         with:
           args: check
+
+  code_coverage:
+    name: "Code coverage report"
+    if: github.event_name == 'pull_request' # Do not run when workflow is triggered by push to main branch
+    runs-on: ubuntu-latest
+    needs: main
+    permissions:
+      contents: read
+      actions: read  # to download code coverage results from "main" job
+      pull-requests: write # write permission needed to comment on PR
+    steps:
+      - name: Check new code coverage
+        uses: fgrosse/go-coverage-report@v1.2.0
+        with:
+          coverage-artifact-name: ${{ env.CODE_COVERAGE_ARTIFACT_NAME }}
+          coverage-file-name: ${{ env.CODE_COVERAGE_FILE_NAME }}
+          root-package: 'github.com/stackitcloud/terraform-provider-stackit'

Makefile

@@ -35,7 +35,7 @@ fmt:
 # TEST
 test:
 	@echo "Running tests for the terraform provider"
-	@cd $(ROOT_DIR)/stackit && go test ./... -count=1 && cd $(ROOT_DIR)
+	@cd $(ROOT_DIR)/stackit && go test ./... -count=1 -coverprofile=coverage.out && cd $(ROOT_DIR)
 
 # Test coverage
 coverage: