diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index 805d063e..cbf66c8c 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -27,9 +27,9 @@ jobs:
 
       - name: autopep8
         run: |
-          autopep8 --in-place --aggressive --recursive ompackagemanager
+          autopep8 --in-place --aggressive --recursive ompackagemanager/ tests/
           if ! git diff --exit-code; then
-            echo "❌ Code not formatted. Please run 'autopep8 --in-place --aggressive --recursive ompackagemanager' locally."
+            echo "❌ Code not formatted. Please run 'autopep8 --in-place --aggressive --recursive ompackagemanager/ tests/' locally."
             exit 1
           else
             echo "✅ Code is properly formatted."
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f4501f0d..e36dc33d 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,6 +8,32 @@ on:
       - master
 
 jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.13']
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: 'pip'
+
+      - name: Install Dependencies
+        run: |
+          pip install -r requirements.txt
+
+      - name: Run unit tests
+        env:
+          GITHUB_AUTH: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          python -m unittest discover -s tests
+
   test-generate:
     runs-on: ubuntu-latest
     permissions:
diff --git a/README.md b/README.md
index 3e667d0f..7ce12a14 100644
--- a/README.md
+++ b/README.md
@@ -174,5 +174,11 @@ All Python code is formatted with
 [autopep8](https://pypi.org/project/autopep8/):
 
 ```bash
-autopep8 --in-place --aggressive --recursive ompackagemanager
+autopep8 --in-place --aggressive --recursive ompackagemanager/ tests/
+```
+
+Unit tests can be run with:
+
+```bash
+python -m unittest discover -s test
 ```
diff --git a/ompackagemanager/check_missing.py b/ompackagemanager/check_missing.py
index d779d70c..0795b2e1 100755
--- a/ompackagemanager/check_missing.py
+++ b/ompackagemanager/check_missing.py
@@ -1,7 +1,6 @@
-from github import Github
+from github import Github, Auth
 import json
 import os
-import pygit2
 
 
 def main():
@@ -12,15 +11,16 @@ def main():
     Prints the missing repositories.
     """
 
-    gh_auth = os.environ["GITHUB_AUTH"]
-    g = Github(gh_auth)
-    data = json.load(open("repos.json"))
+    token = Auth.Token(os.environ["GITHUB_AUTH"])
+    github_api = Github(auth=token)
+    with open("repos.json", "r") as f:
+        data = json.load(f)
     namesInRepos = set()
     for entry in data.values():
         if "github" in entry:
             namesInRepos.add(entry["github"])
 
-    for repo in list(g.get_user("modelica-3rdparty").get_repos()):
+    for repo in list(github_api.get_user("modelica-3rdparty").get_repos()):
         if repo.full_name in namesInRepos:
             continue
         if repo.fork and repo.parent.full_name in namesInRepos:
diff --git a/ompackagemanager/genindex.py b/ompackagemanager/genindex.py
index 184c6c3e..92d5470b 100755
--- a/ompackagemanager/genindex.py
+++ b/ompackagemanager/genindex.py
@@ -116,8 +116,10 @@ def checkProvides(libName, lib, indexdata):
 def main():
     """Generate `index.json` database from `rawdata.json`.
     """
-    repos = json.load(open("repos.json"))
-    rawdata = json.load(open("rawdata.json"))
+    with open("repos.json", "r") as f:
+        repos = json.load(f)
+    with open("rawdata.json", "r") as f:
+        rawdata = json.load(f)
 
     indexdata = {"libs": {}, "mirrors": [
         "https://libraries.openmodelica.org/cache/"]}
diff --git a/ompackagemanager/updateinfo.py b/ompackagemanager/updateinfo.py
index 98db4924..9e3163a7 100755
--- a/ompackagemanager/updateinfo.py
+++ b/ompackagemanager/updateinfo.py
@@ -7,7 +7,7 @@
 import requests
 import shutil
 import zipfile
-from github import Github
+from github import Github, Auth
 from atlassian import Bitbucket
 
 from ompackagemanager import common
@@ -61,12 +61,14 @@ def main():
 
     Queries the repositories where the libraries are stored.
     """
-    gh_auth = os.environ["GITHUB_AUTH"]
-    g = Github(gh_auth)
+
+    token = Auth.Token(os.environ["GITHUB_AUTH"])
+    github_api = Github(auth=token)
 
     omc = OMPython.OMCSessionZMQ()
 
-    data = json.load(open("repos.json"))
+    with open("repos.json", "r") as f:
+        data = json.load(f)
     if os.path.exists("rawdata.json"):
         serverdata = json.load(open("rawdata.json"))
     else:
@@ -96,7 +98,7 @@ def main():
         if "github" in entry or "git" in entry or "zipfiles" in entry:
             if "github" in entry:
                 try:
-                    r = g.get_repo(entry["github"])
+                    r = github_api.get_repo(entry["github"])
                     branches = list((b.name, b.commit.sha)
                                     for b in r.get_branches())
                     tags = list((b.name, b.commit.sha) for b in r.get_tags())
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/test_main.py b/tests/test_main.py
new file mode 100644
index 00000000..6a132de0
--- /dev/null
+++ b/tests/test_main.py
@@ -0,0 +1,36 @@
+import unittest
+from io import StringIO
+import sys
+
+from ompackagemanager import __main__
+
+
+class TestCLI(unittest.TestCase):
+    def test_run_check_missing(self):
+        saved_stdout = sys.stdout
+        try:
+            out = StringIO()
+            sys.stdout = out
+
+            __main__.main(["check-missing"])
+
+            self.assertIn('''modelica-3rdparty/BuildSysPro
+modelica-3rdparty/electrolytemedia
+modelica-3rdparty/ExternalMedia
+modelica-3rdparty/FluidSystemComponents
+modelica-3rdparty/Greenhouses-Library
+modelica-3rdparty/HeatTransferComponents
+modelica-3rdparty/LCC_HVDC
+modelica-3rdparty/MoSDH
+modelica-3rdparty/NeuralNetwork
+modelica-3rdparty/OpenHydraulics
+modelica-3rdparty/ShipSIM
+modelica-3rdparty/SMEHV
+modelica-3rdparty/urdfmodelica
+''', out.getvalue())
+        finally:
+            sys.stdout = saved_stdout
+
+
+if __name__ == "__main__":
+    unittest.main()