Tests, documentation, fixes

tests/support.py

@@ -0,0 +1,12 @@
+import pathlib
+
+INPUT_DIR = "tests/input_files"
+OUTPUT_DIR = "tests/output_files"
+
+def cleanup_output_dir():
+    output_dir = pathlib.Path(OUTPUT_DIR)
+    if output_dir.exists():
+        for f in output_dir.iterdir():
+            f.unlink()
+    else:
+        output_dir.mkdir()