ci: Collect coverage data during tests

MicroOVN snap built in the CI pipeline now supports
coverage instrumentation in its client and daemon binaries.
Test jobs will use this build to collect coverage
data that gets uploaded as an artifact from each job.

After all tests are executed, a new job will collect and
merge coverage data from all tests and produce coverage
report in Cobertura XML format.

Signed-off-by: Martin Kalcok <[email protected]>

.github/workflows/tests.yml

@@ -59,7 +59,10 @@ jobs:
               --classic
 
       - name: Build snap
-        run: make $MICROOVN_SNAP
+        run: |
+          # Build snap with coverage support
+          sed -i 's/MICROOVN_COVERAGE=.*/MICROOVN_COVERAGE="yes"/g' microovn/.build_control
+          make $MICROOVN_SNAP
 
       - name: Upload artifacts
         if: always()
@@ -132,4 +135,60 @@ jobs:
           snap list
 
       - name: Run system tests
-        run: .bats/bats-core/bin/bats tests/${{ matrix.test-file }}
+        run: MICROOVN_COVERAGE_ENABLED=yes make tests/${{ matrix.test-file }}
+
+      - name: Upload test coverage
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.test-file }}_coverage
+          path: ${{ github.workspace }}/.coverage
+          include-hidden-files: true
+          retention-days: 1
+
+  generate-coverage:
+    name: Generate coverage profile
+    needs:
+      - metadata
+      - system-tests
+    # 'ubuntu-latest' currently resolves to '22.04' [0] and since we require "Go >=1.20"
+    # for coverage tools, we need to use explicit 'ubuntu-24.04' image name.
+    # [0] https://github.com/actions/runner-images/issues/10636
+    runs-on: ubuntu-24.04
+    env:
+      COVERAGE_DIR: ${{ github.workspace }}/.coverage
+      COVERAGE_MERGED: ${{ github.workspace }}/.coverage/_merged
+      COVERAGE_MERGED_PROFILE: ${{ github.workspace }}/.coverage/_merged/profile.out
+    steps:
+      - name: Install dependencies
+        run: |
+          sudo apt install -yqq golang
+          go install github.com/boumenot/[email protected]
+
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Download test coverage data
+        uses: actions/download-artifact@v4
+        with:
+          path: ${{ env.COVERAGE_DIR }}
+          pattern: "*_coverage"
+
+      - name: Merge test coverage data
+        run: |
+          mkdir -p "$COVERAGE_MERGED"
+          coverage_inputs=$(find "$COVERAGE_DIR" -type d -name coverage | tr '\n' ',' | sed 's/,$//g')
+          go tool covdata merge -i="$coverage_inputs" -o="$COVERAGE_MERGED"
+          go tool covdata textfmt -i="$COVERAGE_MERGED" -o="$COVERAGE_MERGED_PROFILE"
+
+      - name: Generate cobertura.xml
+        run: |
+          cd microovn/
+          $HOME/go/bin/gocover-cobertura < "$COVERAGE_MERGED_PROFILE" > "$COVERAGE_DIR/cobertura.xml"
+
+      - name: Upload cobertura.xml
+        uses: actions/upload-artifact@v4
+        with:
+          name: cobertura.xml
+          path: ${{ env.COVERAGE_DIR }}/cobertura.xml
+          include-hidden-files: true
+