diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0013481..19c4182 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -67,3 +67,6 @@ jobs:
 
       - name: Validate pre-commit hook
         run: pre-commit try-repo . docstringify
+
+      - name: Run tests
+        run: pytest
diff --git a/pyproject.toml b/pyproject.toml
index 710687f..251e464 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -87,6 +87,26 @@ lint.isort.known-first-party = [
 [tool.codespell]
 ignore-regex = 'https://([\w/\.])+'
 
+[tool.pytest.ini_options]
+filterwarnings = [ "error" ]
+addopts = [
+  "-ra",
+  "-l",
+  "-v",
+  "--tb=short",
+  "--import-mode=importlib",
+  "--strict-markers",
+  "--strict-config",
+  "--cov=docstringify",
+  "--cov=tests",
+  "--no-cov-on-fail",
+  "--cov-report=term-missing",
+]
+xfail_strict = true
+testpaths = [
+  "tests",
+]
+
 [tool.numpydoc_validation]
 checks = [
   "all",  # report on all checks
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..ffd823a
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+"""Test suite for Docstringify."""
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..996076f
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,39 @@
+"""Shared test fixtures."""
+
+from collections import namedtuple
+from textwrap import dedent
+
+import pytest
+
+EXAMPLE_MODULE_NAME = 'example_module'
+EXAMPLE_FUNCTION_NAME = 'function'
+
+DocstringifyTestCase = namedtuple(
+    'DocstringifyTestCase', ('file', 'total_docstrings', 'missing_docstrings')
+)
+
+
+@pytest.fixture
+def function_without_args(tmp_path):
+    """
+    Fixture for generating an example module with a function without args, type
+    annotations, or a docstring.
+    """
+    source_code = dedent(
+        f"""
+        def {EXAMPLE_FUNCTION_NAME}():
+            pass
+        """
+    )
+
+    tmp_file = tmp_path / f'{EXAMPLE_MODULE_NAME}.py'
+    tmp_file.write_text(source_code)
+
+    return DocstringifyTestCase(
+        file=tmp_file,
+        total_docstrings=2,
+        missing_docstrings=[
+            EXAMPLE_MODULE_NAME,
+            f'{EXAMPLE_MODULE_NAME}.{EXAMPLE_FUNCTION_NAME}',
+        ],
+    )
diff --git a/tests/traversal/__init__.py b/tests/traversal/__init__.py
new file mode 100644
index 0000000..c1a7016
--- /dev/null
+++ b/tests/traversal/__init__.py
@@ -0,0 +1 @@
+"""Tests for the docstringify.traversal subpackage."""
diff --git a/tests/traversal/test_visitor.py b/tests/traversal/test_visitor.py
new file mode 100644
index 0000000..710e4a8
--- /dev/null
+++ b/tests/traversal/test_visitor.py
@@ -0,0 +1,23 @@
+"""Test the docstring.traversal.visitor module."""
+
+import pytest
+
+from docstringify.traversal import DocstringVisitor
+
+
+class TestDocstringVisitor:
+    """Test the DocstringVisitor."""
+
+    @pytest.mark.parametrize('file', ['function_without_args'])
+    def test_process_file(self, capsys, request, file):
+        """Test that DocstringVisitor.process_file() correctly processes files."""
+        test_case = request.getfixturevalue(file)
+        visitor = DocstringVisitor(test_case.file)
+        visitor.process_file()
+
+        assert visitor.docstrings_inspected == test_case.total_docstrings
+        assert len(visitor.missing_docstrings) == len(test_case.missing_docstrings)
+
+        stderr = capsys.readouterr().err.strip().split('\n')
+        for missing_docstring in test_case.missing_docstrings:
+            assert f'{missing_docstring} is missing a docstring' in stderr