diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4117dcd..e95b206 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,13 +19,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3.5.3
+        uses: actions/checkout@v3
 
       - name: Install Poetry
         run: pipx install poetry==${{ env.POETRY_VERSION }}
 
       - name: Set up Python with Poetry cache
-        uses: actions/setup-python@v4.6.1
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ env.PYTHON_VERSION }}
           cache: poetry
@@ -54,4 +54,7 @@ jobs:
         run: poetry run mypy paramdb tests
 
       - name: Test (Pytest)
-        run: poetry run pytest
+        run: poetry run pytest --cov=paramdb --cov-report=xml
+
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v3
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 3cb1a84..9bec610 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3.5.3
+        uses: actions/checkout@v3
 
       - name: Install Poetry
         run: pipx install poetry==${{ env.POETRY_VERSION }}
@@ -22,7 +22,7 @@ jobs:
         run: poetry build
 
       - name: Upload package artifact
-        uses: actions/upload-artifact@v3.1.2
+        uses: actions/upload-artifact@v3
         with:
           name: paramdb-release
           path: dist
@@ -36,10 +36,10 @@ jobs:
     permissions:
       id-token: write
     steps:
-      - uses: actions/download-artifact@v3.0.2
+      - uses: actions/download-artifact@v3
         with:
           name: paramdb-release
           path: dist
 
       - name: Publish to PyPI
-        uses: pypa/gh-action-pypi-publish@v1.8.6
+        uses: pypa/gh-action-pypi-publish@release/v1
diff --git a/.gitignore b/.gitignore
index 872d753..6194349 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,6 +13,8 @@ jupyter_execute/
 __pycache__/
 .mypy_cache/
 .pytest_cache/
+.coverage
+coverage.xml
 
 # Database files
 *.db
diff --git a/paramdb/_database.py b/paramdb/_database.py
index 1e6ce87..a77e317 100644
--- a/paramdb/_database.py
+++ b/paramdb/_database.py
@@ -165,13 +165,13 @@ def commit(self, message: str, data: T) -> int:
     @overload
     def load(
         self, commit_id: int | None = None, *, load_classes: Literal[True] = True
-    ) -> T:
+    ) -> T:  # pragma: no cover
         ...
 
     @overload
     def load(
         self, commit_id: int | None = None, *, load_classes: Literal[False]
-    ) -> dict[str, Any]:
+    ) -> dict[str, Any]:  # pragma: no cover
         ...
 
     def load(self, commit_id: int | None = None, *, load_classes: bool = True) -> Any:
diff --git a/paramdb/_param_data/_collections.py b/paramdb/_param_data/_collections.py
index 4b26492..2054ff6 100644
--- a/paramdb/_param_data/_collections.py
+++ b/paramdb/_param_data/_collections.py
@@ -61,22 +61,22 @@ def __init__(self, iterable: Iterable[T] | None = None) -> None:
                 self._add_child(item)
 
     @overload
-    def __getitem__(self, index: SupportsIndex) -> T:
+    def __getitem__(self, index: SupportsIndex) -> T:  # pragma: no cover
         ...
 
     @overload
-    def __getitem__(self, index: slice) -> list[T]:
+    def __getitem__(self, index: slice) -> list[T]:  # pragma: no cover
         ...
 
     def __getitem__(self, index: Any) -> Any:
         return self._contents[index]
 
     @overload
-    def __setitem__(self, index: SupportsIndex, value: T) -> None:
+    def __setitem__(self, index: SupportsIndex, value: T) -> None:  # pragma: no cover
         ...
 
     @overload
-    def __setitem__(self, index: slice, value: Iterable[T]) -> None:
+    def __setitem__(self, index: slice, value: Iterable[T]) -> None:  # pragma: no cover
         ...
 
     def __setitem__(self, index: SupportsIndex | slice, value: Any) -> None:
diff --git a/paramdb/_param_data/_dataclasses.py b/paramdb/_param_data/_dataclasses.py
index 72df930..9ce036b 100644
--- a/paramdb/_param_data/_dataclasses.py
+++ b/paramdb/_param_data/_dataclasses.py
@@ -29,7 +29,7 @@ def __setitem__(self, name: str, value: Any) -> None:
 
     @property
     @abstractmethod
-    def last_updated(self) -> datetime | None:
+    def last_updated(self) -> datetime | None:  # pragma: no cover
         ...
 
     def to_dict(self) -> dict[str, Any]:
diff --git a/poetry.lock b/poetry.lock
index e34d8a8..9e740d2 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.4.2 and should not be changed by hand.
 
 [[package]]
 name = "alabaster"
@@ -458,6 +458,82 @@ lint = ["black (>=22.6.0)", "mdformat (>0.7)", "mdformat-gfm (>=0.3.5)", "ruff (
 test = ["pytest"]
 typing = ["mypy (>=0.990)"]
 
+[[package]]
+name = "coverage"
+version = "7.2.7"
+description = "Code coverage measurement for Python"
+category = "dev"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "coverage-7.2.7-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:d39b5b4f2a66ccae8b7263ac3c8170994b65266797fb96cbbfd3fb5b23921db8"},
+    {file = "coverage-7.2.7-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:6d040ef7c9859bb11dfeb056ff5b3872436e3b5e401817d87a31e1750b9ae2fb"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:ba90a9563ba44a72fda2e85302c3abc71c5589cea608ca16c22b9804262aaeb6"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_5_i686.manylinux1_i686.manylinux_2_17_i686.manylinux2014_i686.whl", hash = "sha256:e7d9405291c6928619403db1d10bd07888888ec1abcbd9748fdaa971d7d661b2"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:31563e97dae5598556600466ad9beea39fb04e0229e61c12eaa206e0aa202063"},
+    {file = "coverage-7.2.7-cp310-cp310-musllinux_1_1_aarch64.whl", hash = "sha256:ebba1cd308ef115925421d3e6a586e655ca5a77b5bf41e02eb0e4562a111f2d1"},
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+    {file = "coverage-7.2.7-cp39-cp39-win32.whl", hash = "sha256:7ee7d9d4822c8acc74a5e26c50604dff824710bc8de424904c0982e25c39c6cb"},
+    {file = "coverage-7.2.7-cp39-cp39-win_amd64.whl", hash = "sha256:eb393e5ebc85245347950143969b241d08b52b88a3dc39479822e073a1a8eb27"},
+    {file = "coverage-7.2.7-pp37.pp38.pp39-none-any.whl", hash = "sha256:b7b4c971f05e6ae490fef852c218b0e79d4e52f79ef0c8475566584a8fb3e01d"},
+    {file = "coverage-7.2.7.tar.gz", hash = "sha256:924d94291ca674905fe9481f12294eb11f2d3d3fd1adb20314ba89e94f44ed59"},
+]
+
+[package.dependencies]
+tomli = {version = "*", optional = true, markers = "python_full_version <= \"3.11.0a6\" and extra == \"toml\""}
+
+[package.extras]
+toml = ["tomli"]
+
 [[package]]
 name = "debugpy"
 version = "1.6.7"
@@ -1799,6 +1875,25 @@ tomli = {version = ">=1.0.0", markers = "python_version < \"3.11\""}
 [package.extras]
 testing = ["argcomplete", "attrs (>=19.2.0)", "hypothesis (>=3.56)", "mock", "nose", "pygments (>=2.7.2)", "requests", "xmlschema"]
 
+[[package]]
+name = "pytest-cov"
+version = "4.1.0"
+description = "Pytest plugin for measuring coverage."
+category = "dev"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "pytest-cov-4.1.0.tar.gz", hash = "sha256:3904b13dfbfec47f003b8e77fd5b589cd11904a21ddf1ab38a64f204d6a10ef6"},
+    {file = "pytest_cov-4.1.0-py3-none-any.whl", hash = "sha256:6ba70b9e97e69fcc3fb45bfeab2d0a138fb65c4d0d6a41ef33983ad114be8c3a"},
+]
+
+[package.dependencies]
+coverage = {version = ">=5.2.1", extras = ["toml"]}
+pytest = ">=4.6"
+
+[package.extras]
+testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtualenv"]
+
 [[package]]
 name = "python-dateutil"
 version = "2.8.2"
@@ -2617,4 +2712,4 @@ astropy = ["astropy"]
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.10"
-content-hash = "f1f0fb350f1e6f978a09e5a8dd4207c8d9b491f540ee30652ba45fd05272c134"
+content-hash = "f788390b55e294b895db530b519711adf4360b9a67a14a02765800cffb3b4e69"
diff --git a/pyproject.toml b/pyproject.toml
index 4d64bd8..c1d2101 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,6 +19,7 @@ astropy = ["astropy"]
 
 [tool.poetry.group.dev.dependencies]
 pytest = "^7.3.1"
+pytest-cov = "^4.1.0"
 flake8 = "^6.0.0"
 pylint = "^2.17.4"
 mypy = "^1.3.0"