diff --git a/test/filename_matching.py b/test/filename_matching.py
new file mode 100644
index 000000000..51cedf03c
--- /dev/null
+++ b/test/filename_matching.py
@@ -0,0 +1,57 @@
+import os
+import re
+import glob
+import sys
+
+
+def check_src_files_have_test():
+    missing_test_files = []
+
+    excluded = ['mitmproxy/contrib/', 'mitmproxy/test/', 'mitmproxy/tools/', 'mitmproxy/platform/']
+    src_files = glob.glob('mitmproxy/**/*.py', recursive=True) + glob.glob('pathod/**/*.py', recursive=True)
+    src_files = [f for f in src_files if os.path.basename(f) != '__init__.py']
+    src_files = [f for f in src_files if not any(os.path.normpath(p) in f for p in excluded)]
+    for f in src_files:
+        p = os.path.join("test", os.path.dirname(f), "test_" + os.path.basename(f))
+        if not os.path.isfile(p):
+            missing_test_files.append((f, p))
+
+    return missing_test_files
+
+
+def check_test_files_have_src():
+    unknown_test_files = []
+
+    excluded = ['test/mitmproxy/data/', 'test/mitmproxy/net/data/', '/tservers.py']
+    test_files = glob.glob('test/mitmproxy/**/*.py', recursive=True) + glob.glob('test/pathod/**/*.py', recursive=True)
+    test_files = [f for f in test_files if os.path.basename(f) != '__init__.py']
+    test_files = [f for f in test_files if not any(os.path.normpath(p) in f for p in excluded)]
+    for f in test_files:
+        p = os.path.join(re.sub('^test/', '', os.path.dirname(f)), re.sub('^test_', '', os.path.basename(f)))
+        if not os.path.isfile(p):
+            unknown_test_files.append((f, p))
+
+    return unknown_test_files
+
+
+def main():
+    exitcode = 0
+
+    missing_test_files = check_src_files_have_test()
+    if missing_test_files:
+        exitcode += 1
+        for f, p in sorted(missing_test_files):
+            print("{} MUST have a matching test file: {}".format(f, p))
+
+    unknown_test_files = check_test_files_have_src()
+    if unknown_test_files:
+        # TODO: enable this in the future
+        # exitcode += 1
+        for f, p in sorted(unknown_test_files):
+            print("{} DOES NOT MATCH a source file! Expected to find: {}".format(f, p))
+
+    sys.exit(exitcode)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tox.ini b/tox.ini
index d798c11a5..1c5e1b963 100644
--- a/tox.ini
+++ b/tox.ini
@@ -30,6 +30,7 @@ commands = sphinx-build -W -b html -d {envtmpdir}/doctrees . {envtmpdir}/html
 commands =
   mitmdump --version
   flake8 --jobs 8 mitmproxy pathod examples test release
+  python3 test/filename_matching.py
   rstcheck README.rst
   mypy --ignore-missing-imports --follow-imports=skip \
     mitmproxy/addons/ \