tests: Add test for PreviewWidget
The test fails currently because of the mainloop freezing, see issue #2278 (closed).
If you comment out this line in the test, it passes:
original_preview_uri(preview_widget, uri)
This is the PreviewWidget.preview_uri
method, which calls _handle_new_asset
which calls GES.UriClipAsset.request_sync(uri)
which blocks!
Edited by Alexandru Băluț