How to test file inputs with Cypress?

How can I write an e2e test of flow that requires interaction with the file Input DOM element?

If it's a text input I can interact with it (check value, set value) etc as its a DOM component. But If I have a File Input element, I am guessing that the interaction is limited till I can open the dialog to select a File. I can't move forward and select the file I want to upload as the dialog would be native and not some browser element.

So how would I test that a user can correctly upload a file from my site? I am using Cypress to write my e2e tests.

it('Testing picture uploading', () => {
    cy.fixture('testPicture.png').then(fileContent => {
        cy.get('input[type="file"]').attachFile({
            fileContent: fileContent.toString(),
            fileName: 'testPicture.png',
            mimeType: 'image/png'
        });
    });
});

Use cypress file upload package: https://www.npmjs.com/package/cypress-file-upload

Note: testPicture.png must be in fixture folder of cypress

For me the easier way to do this is using this cypress file upload package

Install it:

npm install --save-dev cypress-file-upload

Then add this line to your project's cypress/support/commands.js:

import 'cypress-file-upload';

Now you can do:

const fixtureFile = 'photo.png';
cy.get('[data-cy="file-input"]').attachFile(fixtureFile);

photo.png must be in cypress/fixtures/

For more examples checkout the Usage section on README of the package.

With this approach/hack you can actually make it: https://github.com/javieraviles/cypress-upload-file-post-form

It is based on different answers from the aformentioned thread https://github.com/cypress-io/cypress/issues/170

First scenario (upload_file_to_form_spec.js):

I want to test a UI where a file has to be selected/uploaded before submitting the form. Include the following code in your "commands.js" file within the cypress support folder, so the command cy.upload_file() can be used from any test:

Cypress.Commands.add('upload_file', (fileName, fileType, selector) => {
    cy.get(selector).then(subject => {
        cy.fixture(fileName, 'hex').then((fileHex) => {

            const fileBytes = hexStringToByte(fileHex);
            const testFile = new File([fileBytes], fileName, {
                type: fileType
            });
            const dataTransfer = new DataTransfer()
            const el = subject[0]

            dataTransfer.items.add(testFile)
            el.files = dataTransfer.files
        })
    })
})

// UTILS
function hexStringToByte(str) {
    if (!str) {
        return new Uint8Array();
    }

    var a = [];
    for (var i = 0, len = str.length; i < len; i += 2) {
        a.push(parseInt(str.substr(i, 2), 16));
    }

    return new Uint8Array(a);
}

Then, in case you want to upload an excel file, fill in other inputs and submit the form, the test would be something like this:

describe('Testing the excel form', function () {
    it ('Uploading the right file imports data from the excel successfully', function() {

    const testUrl = 'http://localhost:3000/excel_form';
    const fileName = 'your_file_name.xlsx';
    const fileType = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet';
    const fileInput = 'input[type=file]';

    cy.visit(testUrl);
    cy.upload_file(fileName, fileType, fileInput);
    cy.get('#other_form_input2').type('input_content2');
    .
    .
    .
    cy.get('button').contains('Submit').click();

    cy.get('.result-dialog').should('contain', 'X elements from the excel where successfully imported');
})

})

How to test file inputs with Cypress?

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