Add Codecov support for code coverage reporting (#24)

- Add coverage job to CI workflow using cargo-tarpaulin
- Create codecov.yml configuration with:
  - Project and patch coverage thresholds
  - PR comment layout configuration
  - Unit test flags for crates/aptos-sdk/src/
  - Exclusions for examples and test files
  - GitHub Checks annotations enabled

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: gregnazario

.github/workflows/ci.yml

@@ -217,6 +217,37 @@ jobs:
       - name: Check MSRV
         run: cargo check -p aptos-sdk
 
+  coverage:
+    name: Code Coverage
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: "1.90"
+      
+      - name: Cache cargo
+        uses: Swatinem/rust-cache@v2
+      
+      - name: Install cargo-tarpaulin
+        run: cargo install cargo-tarpaulin
+      
+      - name: Run coverage
+        run: |
+          cargo tarpaulin -p aptos-sdk --features "full" --skip-clean --out Xml --out Html --output-dir target/coverage
+        working-directory: crates/aptos-sdk
+      
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          files: crates/aptos-sdk/target/coverage/cobertura.xml
+          flags: unittests
+          name: aptos-sdk-coverage
+          fail_ci_if_error: false
+          verbose: true
+
   security-audit:
     name: Security Audit
     runs-on: ubuntu-latest

codecov.yml

@@ -0,0 +1,51 @@
+# Codecov configuration for aptos-sdk
+# https://docs.codecov.com/docs/codecovyml-reference
+
+coverage:
+  # Coverage status checks
+  status:
+    project:
+      default:
+        # Require coverage to not drop by more than 1%
+        threshold: 1%
+        # Only fail if coverage drops significantly
+        target: auto
+    patch:
+      default:
+        # New code should have at least 50% coverage
+        target: 50%
+        # Allow some flexibility for patches
+        threshold: 5%
+
+  # Precision of coverage percentage
+  precision: 2
+  
+  # Round coverage percentage
+  round: down
+
+# Comment configuration for PRs
+comment:
+  # Post coverage report as a PR comment
+  layout: "reach,diff,flags,files"
+  behavior: default
+  require_changes: true
+  require_base: false
+  require_head: true
+
+# Flags for different test types
+flags:
+  unittests:
+    paths:
+      - crates/aptos-sdk/src/
+    carryforward: true
+
+# Ignore certain paths from coverage
+ignore:
+  - "crates/aptos-sdk/examples/**"
+  - "crates/aptos-sdk/tests/**"
+  - "**/tests/**"
+  - "**/*_test.rs"
+
+# GitHub Checks annotations
+github_checks:
+  annotations: true