When writing application tests, it’s important to make them as realistic as possible. If your app allows users to upload files, your tests should also cover that flow. Otherwise, you risk shipping code that works fine with plain form fields but breaks the moment a real file upload is involved.

That’s where test fixtures come in. A fixture is just a dummy file (like a PDF or image) that lives in your test suite and can be used over and over in tests. Fixtures don’t need to be large or complex - just valid enough for Symfony (and your validators) to accept them as real uploads.

Symfony gives us a handy tool for simulating uploads in tests: the UploadedFile class. Normally, Symfony creates UploadedFile objects automatically when a real user uploads a file via a browser. In tests, we can create one manually:

• Point it to a real file in our /tests/fixtures/ folder.
• Pretend it was uploaded with a filename and MIME type (e.g. test_cv.pdf, application/pdf).
• Enable test mode so Symfony doesn’t complain that the file wasn’t uploaded via HTTP.

This means we can write application tests that submit entire forms - including file uploads - with confidence.

In our example, we attach a dummy PDF to the job application form. This makes our test a true reflection of what happens in production: a candidate fills out their details and uploads a CV. If anything in that process breaks (mapping, validation, request handling), the test will catch it.

By including file uploads in your test suite, you cover one of the trickiest parts of web applications and prevent nasty surprises in production.