Allow to chain commands to fill an input file in cypress

README.md

usage

    cy.get('input[type=file]').selectFile('testDocument.pdf');

index.js

function getFixtureBlob(fileUrl, type = 'application/pdf') {
  return cy.fixture(fileUrl, 'base64').then(Cypress.Blob.base64StringToBlob);
}

Cypress.Commands.add('selectFile', { prevSubject: true },
  (selector, fileUrl) => {
    const obj = cy.wrap(selector);
    return obj.then(subject => {
      return getFixtureBlob(fileUrl).then(blob => {
        return cy.window().then(win => {
          const name = fileUrl.split('/').pop();
          const testFile = new win.File([blob], name, { type: blob.type });
          const dataTransfer = new win.DataTransfer();
          dataTransfer.items.add(testFile);
          const el = subject[0];
          el.files = dataTransfer.files;
          return subject;
        });
      });
    });
  }
);