add coverage report (#24)

.github/workflows/ci.yml

@@ -86,3 +86,27 @@ jobs:
         uses: Swatinem/rust-cache@v2
       - name: Run cargo test --features fips
         run: cargo test --tests --features fips -- --test-threads=1
+
+  coverage:
+    name: Coverage
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+      - name: Install toolchain
+        uses: dtolnay/rust-toolchain@v1
+        with:
+          toolchain: stable
+          components: llvm-tools
+      - name: Cache build artifacts
+        uses: Swatinem/rust-cache@v2
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - name: Generate coverage
+        run: cargo llvm-cov --lcov --output-path lcov.info
+      - name: Report to codecov.io
+        uses: codecov/codecov-action@v5
+        with:
+          files: lcov.info
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: false