added overwrite functionality

tests/test_io_handlers.py

@@ -101,6 +101,21 @@ def test_clear(tmp_path: Path):
     assert not zpath.exists()
 
 
+def test_overwrite(tmp_path: Path):
+    params = Parameters(**PARAMS)
+    zpath = tmp_path / "file.zip"
+    _ = propagation(zpath, params)
+    orig_file = zpath.read_bytes()
+
+    with pytest.raises(FileExistsError):
+        _ = propagation(zpath, params)
+
+    _ = propagation(zpath, params, overwrite=True)
+
+    assert zpath.read_bytes() != orig_file
+    assert len(zpath.read_bytes()) == len(orig_file)
+
+
 def test_zip_bundle(tmp_path: Path):
     params = Parameters(**PARAMS)