3.5.0: File upload doesn't work with DataTransfer()

Current behavior:

I have a feature in my app where the user should upload an file as thier user image. Within my cypress test I faking the file upload dialog with the DataTransfer shown below. With 3.4.1 this works fine, but 3.5.0 looks to break this behavior. I investigated the the file is written into the input element, when I log this with console.error. But in my app, the file change handler is not fired. So something in between is going wrong.

Maybe there is also a much better for mocking file uploads.

Thanks for you help 😃

cy.get('.toolbar').within(() => {
  cy.fixture('picture.jpg', 'binary')
    .then((binary) => Cypress.Blob.binaryStringToBlob(binary))
    .then((blob) => {
      cy.get('input[type=file]').then((input) => {
        const dataTransfer = new DataTransfer();
        dataTransfer.items.add(new File([blob], 'me.jpg', {type: 'image/jpeg'}));
        input[0].files = dataTransfer.files;
      });
    });
  cy.get('.btn').contains('Speichern').should('be.visible').click();
});

Desired behavior:

Blob should correctly written to input element and button becomes clickable.

Steps to reproduce: (app code and test code)

see above

Versions

cypress@3.5.0 (Version 3.4.1 works fine)

[yuki-93]

Adding input[0].dispatchEvent(new Event('change', {bubbles: true})); as suggested in one comment worked for me. Thanks for your help 😃

[yuki-93]

The file change event would validates the image (size, type and dimensions) and than enables the submit button, to be clickable. So the click is necessary. In another test, I issue the ajax calls directly, which works fine.