Add CI workflow for tests, lint, and coverage

Runs pytest across Python 3.10-3.13 with ruff lint,
uploads coverage to Codecov on main branch.

Author: bevenky

.github/workflows/tests.yml

@@ -0,0 +1,56 @@
+name: Tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: pip install -e ".[dev]"
+
+      - name: Lint
+        run: ruff check src/ tests/
+
+      - name: Run tests
+        run: pytest tests/ -v --tb=short
+
+  coverage:
+    runs-on: ubuntu-latest
+    needs: test
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: pip install -e ".[dev]" pytest-cov
+
+      - name: Run tests with coverage
+        run: pytest tests/ --cov=plivo_agent --cov-report=xml
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          file: coverage.xml
+          fail_ci_if_error: false
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}