diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 2a2028c..de50d23 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -4,6 +4,9 @@ on: [pull_request, workflow_dispatch]
 
 jobs:
   test:
+    strategy:
+      matrix:
+        env: ["py39", "py310", "py311", "py312", "py313"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
@@ -11,11 +14,6 @@ jobs:
         with:
           fetch-depth: 1
 
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version-file: .python-version
-
       - name: Set up uv
         uses: astral-sh/setup-uv@v5
         with:
@@ -25,4 +23,4 @@ jobs:
         run: uv sync --group dev
 
       - name: Test with pytest
-        run: uv run pytest
+        run: uv run tox -e ${{ matrix.env }}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0eb1834..5b8b52b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Automatic testing across all supported Python versions
+
 ### Fixed
 
 - Compatibility with Python 3.9 and Python 3.10
diff --git a/README.md b/README.md
index fee11f6..c65f2df 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ dependencies = [
 
 ### Supported Python Versions
 
-While we only actively test under Python 3.13, we strive to support all versions from Python 3.9 and above.
+Python version 3.9 and above.
 
 ## Usage
 
diff --git a/pyproject.toml b/pyproject.toml
index a4e8f1b..82fccff 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,13 +25,15 @@ Documentation = "https://developer.todoist.com/rest/"
 
 [dependency-groups]
 dev = [
-  "pytest>=8.0.0,<9",
   "pre-commit>=4.0.0,<5",
+  "pytest>=8.0.0,<9",
+  "pytest-asyncio>=0.26.0,<0.27",
+  "tox>=4.15.1,<5",
+  "tox-uv>=1.25.0,<2",
   "mypy~=1.11",
+  "ruff>=0.11.0,<0.12",
   "responses>=0.25.3,<0.26",
-  "pytest-asyncio>=0.26.0,<0.27",
   "types-requests~=2.32",
-  "ruff>=0.11.0,<0.12",
 ]
 
 docs = [
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..2cbcbeb
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,9 @@
+[tox]
+envlist = py39,py310,py311,py312,py313
+
+[testenv]
+runner = uv-venv-lock-runner
+deps =
+    pytest
+commands =
+    pytest {posargs}
diff --git a/uv.lock b/uv.lock
index 06ad10a..bb3c658 100644
--- a/uv.lock
+++ b/uv.lock
@@ -33,6 +33,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/0c/37/fb6973edeb700f6e3d6ff222400602ab1830446c25c7b4676d8de93e65b8/backrefs-5.8-py39-none-any.whl", hash = "sha256:a66851e4533fb5b371aa0628e1fee1af05135616b86140c9d787a2ffdf4b8fdc", size = 380336 },
 ]
 
+[[package]]
+name = "cachetools"
+version = "5.5.2"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/6c/81/3747dad6b14fa2cf53fcf10548cf5aea6913e96fab41a3c198676f8948a5/cachetools-5.5.2.tar.gz", hash = "sha256:1a661caa9175d26759571b2e19580f9d6393969e5dfca11fdb1f947a23e640d4", size = 28380 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/72/76/20fa66124dbe6be5cafeb312ece67de6b61dd91a0247d1ea13db4ebb33c2/cachetools-5.5.2-py3-none-any.whl", hash = "sha256:d26a22bcc62eb95c3beabd9f1ee5e820d3d2704fe2967cbe350e20c8ffcd3f0a", size = 10080 },
+]
+
 [[package]]
 name = "certifi"
 version = "2025.1.31"
@@ -51,6 +60,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/c5/55/51844dd50c4fc7a33b653bfaba4c2456f06955289ca770a5dbd5fd267374/cfgv-3.4.0-py2.py3-none-any.whl", hash = "sha256:b7265b1f29fd3316bfcd2b330d63d024f2bfd8bcb8b0272f8e19a504856c48f9", size = 7249 },
 ]
 
+[[package]]
+name = "chardet"
+version = "5.2.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/f3/0d/f7b6ab21ec75897ed80c17d79b15951a719226b9fababf1e40ea74d69079/chardet-5.2.0.tar.gz", hash = "sha256:1b3b6ff479a8c414bc3fa2c0852995695c4a026dcd6d0633b2dd092ca39c1cf7", size = 2069618 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/38/6f/f5fbc992a329ee4e0f288c1fe0e2ad9485ed064cac731ed2fe47dcc38cbf/chardet-5.2.0-py3-none-any.whl", hash = "sha256:e1cf59446890a00105fe7b7912492ea04b6e6f06d4b742b2c788469e34c82970", size = 199385 },
+]
+
 [[package]]
 name = "charset-normalizer"
 version = "3.4.1"
@@ -617,6 +635,19 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/eb/f5/b9e2a42aa8f9e34d52d66de87941ecd236570c7ed2e87775ed23bbe4e224/pymdown_extensions-10.14.3-py3-none-any.whl", hash = "sha256:05e0bee73d64b9c71a4ae17c72abc2f700e8bc8403755a00580b49a4e9f189e9", size = 264467 },
 ]
 
+[[package]]
+name = "pyproject-api"
+version = "1.9.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "packaging" },
+    { name = "tomli", marker = "python_full_version < '3.11'" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/7e/66/fdc17e94486836eda4ba7113c0db9ac7e2f4eea1b968ee09de2fe75e391b/pyproject_api-1.9.0.tar.gz", hash = "sha256:7e8a9854b2dfb49454fae421cb86af43efbb2b2454e5646ffb7623540321ae6e", size = 22714 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/b0/1d/92b7c765df46f454889d9610292b0ccab15362be3119b9a624458455e8d5/pyproject_api-1.9.0-py3-none-any.whl", hash = "sha256:326df9d68dea22d9d98b5243c46e3ca3161b07a1b9b18e213d1e24fd0e605766", size = 13131 },
+]
+
 [[package]]
 name = "pytest"
 version = "8.3.5"
@@ -805,6 +836,8 @@ dev = [
     { name = "pytest-asyncio" },
     { name = "responses" },
     { name = "ruff" },
+    { name = "tox" },
+    { name = "tox-uv" },
     { name = "types-requests" },
 ]
 docs = [
@@ -828,6 +861,8 @@ dev = [
     { name = "pytest-asyncio", specifier = ">=0.26.0,<0.27" },
     { name = "responses", specifier = ">=0.25.3,<0.26" },
     { name = "ruff", specifier = ">=0.11.0,<0.12" },
+    { name = "tox", specifier = ">=4.15.1,<5" },
+    { name = "tox-uv", specifier = ">=1.25.0,<2" },
     { name = "types-requests", specifier = "~=2.32" },
 ]
 docs = [
@@ -875,6 +910,43 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/6e/c2/61d3e0f47e2b74ef40a68b9e6ad5984f6241a942f7cd3bbfbdbd03861ea9/tomli-2.2.1-py3-none-any.whl", hash = "sha256:cb55c73c5f4408779d0cf3eef9f762b9c9f147a77de7b258bef0a5628adc85cc", size = 14257 },
 ]
 
+[[package]]
+name = "tox"
+version = "4.25.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "cachetools" },
+    { name = "chardet" },
+    { name = "colorama" },
+    { name = "filelock" },
+    { name = "packaging" },
+    { name = "platformdirs" },
+    { name = "pluggy" },
+    { name = "pyproject-api" },
+    { name = "tomli", marker = "python_full_version < '3.11'" },
+    { name = "typing-extensions", marker = "python_full_version < '3.11'" },
+    { name = "virtualenv" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/fe/87/692478f0a194f1cad64803692642bd88c12c5b64eee16bf178e4a32e979c/tox-4.25.0.tar.gz", hash = "sha256:dd67f030317b80722cf52b246ff42aafd3ed27ddf331c415612d084304cf5e52", size = 196255 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/f9/38/33348de6fc4b1afb3d76d8485c8aecbdabcfb3af8da53d40c792332e2b37/tox-4.25.0-py3-none-any.whl", hash = "sha256:4dfdc7ba2cc6fdc6688dde1b21e7b46ff6c41795fb54586c91a3533317b5255c", size = 172420 },
+]
+
+[[package]]
+name = "tox-uv"
+version = "1.25.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "packaging" },
+    { name = "tox" },
+    { name = "typing-extensions", marker = "python_full_version < '3.10'" },
+    { name = "uv" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/5d/3a/3e445f25978a716ba6674f33f687d9336d0312086a277a778a5e9e9220d7/tox_uv-1.25.0.tar.gz", hash = "sha256:59ee5e694c41fef7bbcf058f22a5f9b6a8509698def2ea60c08554f4e36b9fcc", size = 21114 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/3c/a7/f5c29e0e6faaccefcab607f672b176927144e9412c8183d21301ea2a6f6c/tox_uv-1.25.0-py3-none-any.whl", hash = "sha256:50cfe7795dcd49b2160d7d65b5ece8717f38cfedc242c852a40ec0a71e159bf7", size = 16431 },
+]
+
 [[package]]
 name = "types-requests"
 version = "2.32.0.20250328"
@@ -905,6 +977,31 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/c8/19/4ec628951a74043532ca2cf5d97b7b14863931476d117c471e8e2b1eb39f/urllib3-2.3.0-py3-none-any.whl", hash = "sha256:1cee9ad369867bfdbbb48b7dd50374c0967a0bb7710050facf0dd6911440e3df", size = 128369 },
 ]
 
+[[package]]
+name = "uv"
+version = "0.6.16"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/28/ba/1a5e6dcaa5412081fc900f44403f61188c035565e7df5bf658c266c90539/uv-0.6.16.tar.gz", hash = "sha256:965312f4fd9dda88f688e23edad34324abd1e094acfc813bb476f8bf9a18e44b", size = 3269694 }
+wheels = [
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 version = "20.29.3"