diff --git a/noxfile.py b/noxfile.py
new file mode 100644
index 0000000..70e6593
--- /dev/null
+++ b/noxfile.py
@@ -0,0 +1,6 @@
+import nox
+
+@nox.session()
+def tests(session):
+    session.install(".[tests]")
+    session.run("pytest", '--driver=firefox', *session.posargs)
diff --git a/pyproject.toml b/pyproject.toml
index 44e6d4c..22fb14f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,3 +55,17 @@ follow_imports = "skip"
 incremental = true
 check_untyped_defs = true
 warn_unused_ignores = true
+
+[project.optional-dependencies]
+tests = [
+    'pytest>=8',
+    'selenium',
+    'pytest-selenium',
+]
+
+[tool.pytest.ini_options]
+minversion = "6.0"
+addopts = "-ra -q"
+testpaths = [
+    "tests",
+]
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..97f95c6
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,33 @@
+import pytest
+import subprocess
+from selenium import webdriver
+from pathlib import Path
+
+
+@pytest.fixture(scope="session")
+def firefox_driver():
+    _driver = webdriver.Firefox()
+    yield _driver
+    _driver.quit()
+
+
+@pytest.fixture(scope="session")
+def chrome_driver():
+    _driver = webdriver.Chrome()
+    yield _driver
+    _driver.quit()
+
+
+@pytest.fixture(autouse=True)
+def run_make_commands(request):
+    # Get the directory of the current test file
+    test_dir = request.fspath.dirname
+    cmd = """
+    uv venv && \\
+    . .venv/bin/activate && \\
+    uv pip install -r requirements.txt && \\
+    .venv/bin/sphinx-build -M zundler . _build
+"""
+
+    for d in ["copy-button", "mermaid", "multi-page"]:
+        subprocess.run(cmd.strip(), shell=True, check=True, cwd=Path(test_dir) / d)
diff --git a/tests/copy-button/conf.py b/tests/copy-button/conf.py
new file mode 100644
index 0000000..a159f3b
--- /dev/null
+++ b/tests/copy-button/conf.py
@@ -0,0 +1,12 @@
+from sphinx.application import Sphinx
+
+project = 'copy-button'
+copyright = '2024, Adrian Vollmer'
+author = 'Adrian Vollmer'
+version = '0.0.1'
+
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+
+extensions = [
+    "sphinx_copybutton",
+]
diff --git a/tests/copy-button/index.rst b/tests/copy-button/index.rst
new file mode 100644
index 0000000..44b22fa
--- /dev/null
+++ b/tests/copy-button/index.rst
@@ -0,0 +1,3 @@
+.. code:: python
+
+    Copy me
diff --git a/tests/copy-button/requirements.txt b/tests/copy-button/requirements.txt
new file mode 100644
index 0000000..2276438
--- /dev/null
+++ b/tests/copy-button/requirements.txt
@@ -0,0 +1,3 @@
+sphinx
+sphinx-copybutton
+../..
diff --git a/tests/mermaid/conf.py b/tests/mermaid/conf.py
new file mode 100644
index 0000000..e0aa7b6
--- /dev/null
+++ b/tests/mermaid/conf.py
@@ -0,0 +1,12 @@
+from sphinx.application import Sphinx
+
+project = 'mermaid'
+copyright = '2024, Adrian Vollmer'
+author = 'Adrian Vollmer'
+version = '0.0.1'
+
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+
+extensions = [
+    'sphinxcontrib.mermaid'
+]
diff --git a/tests/mermaid/index.rst b/tests/mermaid/index.rst
new file mode 100644
index 0000000..1493dc0
--- /dev/null
+++ b/tests/mermaid/index.rst
@@ -0,0 +1,17 @@
+.. mermaid::
+
+   sequenceDiagram
+      participant Alice
+      participant Bob
+      Alice->John: Hello John, how are you?
+      loop Healthcheck
+          John->John: Fight against hypochondria
+      end
+      Note right of John: Rational thoughts <br/>prevail...
+      John-->Alice: Great!
+      John->Bob: How about you?
+      Bob-->John: Jolly good!
+
+
+Section
+=======
diff --git a/tests/mermaid/requirements.txt b/tests/mermaid/requirements.txt
new file mode 100644
index 0000000..e33c256
--- /dev/null
+++ b/tests/mermaid/requirements.txt
@@ -0,0 +1,3 @@
+sphinx
+sphinxcontrib-mermaid
+../..
diff --git a/tests/multi-page/conf.py b/tests/multi-page/conf.py
new file mode 100644
index 0000000..0b32a6b
--- /dev/null
+++ b/tests/multi-page/conf.py
@@ -0,0 +1,8 @@
+from sphinx.application import Sphinx
+
+project = 'multi-page'
+copyright = '2024, Adrian Vollmer'
+author = 'Adrian Vollmer'
+version = '0.0.1'
+
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
diff --git a/tests/multi-page/first.rst b/tests/multi-page/first.rst
new file mode 100644
index 0000000..becd46a
--- /dev/null
+++ b/tests/multi-page/first.rst
@@ -0,0 +1,6 @@
+.. _first:
+
+First
+=====
+
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. 
diff --git a/tests/multi-page/index.rst b/tests/multi-page/index.rst
new file mode 100644
index 0000000..5355fc7
--- /dev/null
+++ b/tests/multi-page/index.rst
@@ -0,0 +1,18 @@
+Welcome
+=======
+
+.. toctree::
+    :maxdepth: 2
+    :caption: Contents:
+
+    first
+    second
+    third
+
+
+Chapters
+========
+
+* :ref:`first`
+* :ref:`second`
+* :ref:`third`
diff --git a/tests/multi-page/requirements.txt b/tests/multi-page/requirements.txt
new file mode 100644
index 0000000..9e1dc97
--- /dev/null
+++ b/tests/multi-page/requirements.txt
@@ -0,0 +1,2 @@
+sphinx
+../..
diff --git a/tests/multi-page/second.rst b/tests/multi-page/second.rst
new file mode 100644
index 0000000..0aac8ab
--- /dev/null
+++ b/tests/multi-page/second.rst
@@ -0,0 +1,6 @@
+.. _second:
+
+Second
+======
+
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. 
diff --git a/tests/multi-page/third.rst b/tests/multi-page/third.rst
new file mode 100644
index 0000000..a2c747c
--- /dev/null
+++ b/tests/multi-page/third.rst
@@ -0,0 +1,6 @@
+.. _third:
+
+Third
+=====
+
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. 
diff --git a/tests/test_zundler.py b/tests/test_zundler.py
new file mode 100644
index 0000000..c4b1e6a
--- /dev/null
+++ b/tests/test_zundler.py
@@ -0,0 +1,96 @@
+import time
+from pathlib import Path
+
+from selenium.webdriver.common.by import By
+from selenium.webdriver.common.keys import Keys
+
+
+TEST_DIR = Path(__file__).resolve().parent
+
+
+def test_copy_button(selenium):
+    path = TEST_DIR / "copy-button//_build//zundler//index.html"
+    selenium.get(path.as_uri())
+
+    time.sleep(1)
+
+    assert "copy-button documentation" in selenium.title
+
+    selenium.switch_to.frame("main")
+    # Not sure why there are two buttons, but we need the second one.
+    # The first cannot be clicked by selenium because it's obscured.
+
+    button = selenium.find_element(By.CSS_SELECTOR, "button.copybtn + button.copybtn")
+
+    assert button.get_attribute("data-tooltip") == "Copy"
+    assert "success" not in button.get_attribute("class")
+
+    button.click()
+
+    assert button.get_attribute("data-tooltip") == "Copied!"
+    assert "success" in button.get_attribute("class")
+
+    # Check layout
+    assert button.location["y"] < 55
+    assert button.location["y"] > 45
+
+
+def test_mermaid(selenium):
+    path = TEST_DIR / "mermaid//_build//zundler//index.html"
+    selenium.get(path.as_uri())
+
+    time.sleep(1)
+
+    assert "mermaid documentation" in selenium.title
+
+    selenium.switch_to.frame("main")
+
+    section = selenium.find_element(By.CSS_SELECTOR, "#section")
+    svg = selenium.find_element(By.CSS_SELECTOR, "div.mermaid")
+
+    # Check layout
+    assert svg.size["height"] > 500
+    assert section.location["y"] > 500
+
+
+def test_multi_page(selenium):
+    path = TEST_DIR / "multi-page//_build//zundler//index.html"
+    selenium.get(path.as_uri())
+
+    time.sleep(1)
+
+    assert "multi-page documentation" in selenium.title
+
+    selenium.switch_to.frame("main")
+
+    second_link = selenium.find_element(By.XPATH, "//a[text() = 'Second' and @class = 'reference internal']")
+
+    second_link.click()
+
+    time.sleep(1)
+
+    assert selenium.title.startswith("Second")
+
+
+def test_multi_page_search(selenium):
+    path = TEST_DIR / "multi-page//_build//zundler//index.html"
+    selenium.get(path.as_uri())
+
+    time.sleep(1)
+
+    assert "multi-page documentation" in selenium.title
+
+    selenium.switch_to.frame("main")
+
+    searchbox = selenium.find_element(By.CSS_SELECTOR, "#searchbox input[type='text']")
+
+    searchbox.send_keys("Lorem" + Keys.ENTER)
+    selenium.switch_to.parent_frame()
+    time.sleep(2)
+    selenium.switch_to.frame("main")
+
+    assert selenium.title.startswith("Search")
+
+    span = selenium.find_element(By.CSS_SELECTOR, "span.highlighted")
+
+    assert span.text == "Lorem"