How to Test File Uploads in Vibecoded Apps

Test uploading every file type your app claims to support: images (JPEG, PNG, WebP, SVG), documents (PDF, DOCX), and any other formats. Then test with types that should be rejected — executable files, scripts, and types not on your allow list. AI-generated code often validates file extensions on the client but not on the server, so test by renaming a disallowed file to an allowed extension.

Test size limits by uploading files at, just below, and just above the maximum allowed size. Verify that the error message for oversized files is clear and appears before the upload starts, not after the user waits for a full upload. Also test with zero-byte files and extremely small files, which sometimes cause unexpected behavior.

Upload a large file and verify that a progress indicator appears and advances smoothly. Throttle your network to Slow 3G in DevTools to make the upload take longer and observe the behavior. The progress bar should reflect actual upload progress, not just animate independently. AI-generated progress bars are often decorative and do not track real upload progress.

Test canceling an upload mid-progress. The app should stop the upload, clean up any partial files on the server, and allow the user to try again. Also test what happens when the network drops during an upload — the app should detect the failure, inform the user, and ideally allow resuming where it left off.

After uploading, verify the file is accessible at the URL or location shown in the app. Download it and confirm it matches the original — no corruption or quality loss (unless intentional compression is applied). Check that uploaded files are stored with appropriate access controls: private files should require authentication to access.

Test with files that have special characters in their names, including spaces, Unicode characters, and very long filenames. AI-generated code frequently breaks on these. Also test concurrent uploads of multiple files and verify that all files are stored correctly without overwriting each other.