diff --git a/tests/conftest.py b/tests/conftest.py
index 3be27ba..b81fc56 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1 +1,86 @@
 """Configuration for the pytest test suite."""
+
+from __future__ import annotations
+
+from collections import ChainMap
+
+import pytest
+from markdown.core import Markdown
+from mkdocs import config
+
+try:
+    from mkdocs.config.defaults import get_schema
+except ImportError:
+
+    def get_schema() -> tuple[tuple]:  # noqa: WPS440
+        """Fallback for old versions of MkDocs.
+
+        Returns:
+            The default schema.
+        """
+        return config.DEFAULT_SCHEMA
+
+
+@pytest.fixture(name="mkdocs_conf")
+def fixture_mkdocs_conf(request, tmp_path):
+    """Yield a MkDocs configuration object.
+
+    Parameters:
+        request: Pytest fixture.
+        tmp_path: Pytest fixture.
+
+    Yields:
+        MkDocs config.
+    """
+    conf = config.Config(schema=get_schema())
+    while hasattr(request, "_parent_request") and hasattr(request._parent_request, "_parent_request"):  # noqa: WPS437
+        request = request._parent_request  # noqa: WPS437
+
+    conf_dict = {
+        "site_name": "foo",
+        "site_url": "https://example.org/",
+        "site_dir": str(tmp_path),
+        "plugins": [{"mkdocstrings": {"default_handler": "python"}}],
+        **getattr(request, "param", {}),
+    }
+    # Re-create it manually as a workaround for https://github.com/mkdocs/mkdocs/issues/2289
+    mdx_configs = dict(ChainMap(*conf_dict.get("markdown_extensions", [])))
+
+    conf.load_dict(conf_dict)
+    assert conf.validate() == ([], [])
+
+    conf["mdx_configs"] = mdx_configs
+    conf["markdown_extensions"].insert(0, "toc")  # Guaranteed to be added by MkDocs.
+
+    conf = conf["plugins"]["mkdocstrings"].on_config(conf)
+    conf = conf["plugins"]["autorefs"].on_config(conf)
+    yield conf
+    conf["plugins"]["mkdocstrings"].on_post_build(conf)
+
+
+@pytest.fixture(name="plugin")
+def fixture_plugin(mkdocs_conf):
+    """Return a plugin instance.
+
+    Parameters:
+        mkdocs_conf: Pytest fixture: [tests.conftest.fixture_mkdocs_conf][].
+
+    Returns:
+        mkdocstrings plugin instance.
+    """
+    plugin = mkdocs_conf["plugins"]["mkdocstrings"]
+    plugin.md = Markdown(extensions=mkdocs_conf["markdown_extensions"], extension_configs=mkdocs_conf["mdx_configs"])
+    return plugin
+
+
+@pytest.fixture(name="ext_markdown")
+def fixture_ext_markdown(plugin):
+    """Return a Markdown instance with MkdocstringsExtension.
+
+    Parameters:
+        plugin: Pytest fixture: [tests.conftest.fixture_plugin][].
+
+    Returns:
+        A Markdown instance.
+    """
+    return plugin.md
diff --git a/tests/test_cli.py b/tests/test_cli.py
deleted file mode 100644
index 652c09d..0000000
--- a/tests/test_cli.py
+++ /dev/null
@@ -1,23 +0,0 @@
-"""Tests for the `cli` module."""
-
-import pytest
-
-from mkdocstrings import cli
-
-
-def test_main():
-    """Basic CLI test."""
-    assert cli.main([]) == 0
-
-
-def test_show_help(capsys):
-    """
-    Show help.
-
-    Arguments:
-        capsys: Pytest fixture to capture output.
-    """
-    with pytest.raises(SystemExit):
-        cli.main(["-h"])
-    captured = capsys.readouterr()
-    assert "mkdocstrings-python" in captured.out
diff --git a/tests/test_collector.py b/tests/test_collector.py
new file mode 100644
index 0000000..2351343
--- /dev/null
+++ b/tests/test_collector.py
@@ -0,0 +1,25 @@
+"""Tests for the handlers.python module."""
+
+import pytest
+
+from mkdocstrings.handlers.python.collector import CollectionError, PythonCollector
+
+
+def test_collect_missing_module():
+    """Assert error is raised for missing modules."""
+    collector = PythonCollector()
+    with pytest.raises(CollectionError):
+        collector.collect("aaaaaaaa", {})
+
+
+def test_collect_missing_module_item():
+    """Assert error is raised for missing items within existing modules."""
+    collector = PythonCollector()
+    with pytest.raises(CollectionError):
+        collector.collect("mkdocstrings.aaaaaaaa", {})
+
+
+def test_collect_module():
+    """Assert existing module can be collected."""
+    collector = PythonCollector()
+    assert collector.collect("mkdocstrings", {})
diff --git a/tests/test_themes.py b/tests/test_themes.py
new file mode 100644
index 0000000..779e443
--- /dev/null
+++ b/tests/test_themes.py
@@ -0,0 +1,40 @@
+"""Tests for the different themes we claim to support."""
+
+import sys
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "plugin",
+    [
+        {"theme": "mkdocs"},
+        {"theme": "readthedocs"},
+        {"theme": {"name": "material"}},
+    ],
+    indirect=["plugin"],
+)
+@pytest.mark.parametrize(
+    "module",
+    [
+        "mkdocstrings.extension",
+        "mkdocstrings.inventory",
+        "mkdocstrings.loggers",
+        "mkdocstrings.plugin",
+        "mkdocstrings.handlers.base",
+        "mkdocstrings.handlers.python",
+        "mkdocstrings.handlers.rendering",
+    ],
+)
+@pytest.mark.skipif(sys.version_info < (3, 7), reason="material is not installed on Python 3.6")
+def test_render_themes_templates_python(module, plugin):
+    """Test rendering of a given theme's templates.
+
+    Parameters:
+        module: Parametrized argument.
+        plugin: Pytest fixture: [tests.conftest.fixture_plugin][].
+    """
+    handler = plugin.handlers.get_handler("python")
+    handler.renderer._update_env(plugin.md, plugin.handlers._config)  # noqa: WPS437
+    data = handler.collector.collect(module, {})
+    handler.renderer.render(data, {})