diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 35d3610..17491c0 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -36,4 +36,6 @@ jobs:
           pip install -r requirements-dev.txt
 
       - name: Running ruff
-        run: ruff check vsscale
+        run: |
+          ruff check vsscale
+          ruff check tests
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..1392701
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,34 @@
+name: Test Python code
+
+on: [push, pull_request]
+
+jobs:
+  windows:
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        vs-versions:
+          - 68
+        python-version:
+          - '3.12'
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: |
+          python3 -m pip install --upgrade pip
+          pip install vapoursynth-portable==${{ matrix.vs-versions }}
+          pip install -r requirements.txt
+          pip install -r requirements-dev.txt
+
+      - name: Running tests
+        run: pytest --cov-report=term-missing:skip-covered --cov=vsscale tests
+
+      - name: Coveralls GitHub Action
+        uses: coverallsapp/github-action@v2.3.1
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..03f586d
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,2 @@
+[pytest]
+pythonpath = .
\ No newline at end of file
diff --git a/requirements-dev.txt b/requirements-dev.txt
index a2f94d9..20e28d7 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,3 +1,5 @@
 packaging>=24.0
 pycodestyle>=2.11.1
+pytest>=7.3.1
+pytest-cov>=5.0.0
 ruff>=0.6.5
diff --git a/tests/test_funcs.py b/tests/test_funcs.py
new file mode 100644
index 0000000..a94a0ec
--- /dev/null
+++ b/tests/test_funcs.py
@@ -0,0 +1,26 @@
+from unittest import TestCase
+
+import vapoursynth as vs
+from vskernels import Bicubic, Bilinear
+
+from vsscale import MergeScalers
+
+
+class TestFuncs(TestCase):
+    def test_merge_scalers_downscale(self) -> None:
+        input = vs.core.std.BlankClip(width=1920, height=1080, format=vs.YUV420P8)
+        scaler = MergeScalers((Bicubic, 0.5), (Bilinear, 0.5))
+        output = scaler.scale(input, 1280, 720)
+        self.assertEqual(output.width, 1280)
+        self.assertEqual(output.height, 720)
+        self.assertEqual(output.format.color_family, vs.YUV)
+        self.assertEqual(output.format.bits_per_sample, 8)
+
+    def test_merge_scalers_upscale(self) -> None:
+        input = vs.core.std.BlankClip(width=1280, height=720, format=vs.YUV420P8)
+        scaler = MergeScalers((Bicubic, 0.5), (Bilinear, 0.5))
+        output = scaler.scale(input, 1920, 1080)
+        self.assertEqual(output.width, 1920)
+        self.assertEqual(output.height, 1080)
+        self.assertEqual(output.format.color_family, vs.YUV)
+        self.assertEqual(output.format.bits_per_sample, 8)