As an example of what I'm attempting:

describe('Compare', () => {
 it('target snapshot', () => {
 cy.visit(Cypress.env('TEST_TARGET_URL'));
 cy.matchImage();
 });
 it('source snapshot', () => {
 cy.visit(Cypress.env('TEST_SOURCE_URL'));
 cy.matchImage();
 });
});

Sorry for late response 😞
@notdotscott That's and interesting usecase!
You're right - even if you pass the same title configuration option (as below) you'll get #0 and #1 suffix for each of the images.

cy.matchImage({ title: 'my-title' });

I'm not sure how the API for this feature should look like:

1. It could be done via additional option - I could let you pass preventTitleClashes: false and together with title option you could force tests to use the same title for screenshots. Resulting in comparing images. Your test would look like this:

const title = 'my-screenshot-title';
describe('Compare', () => {
 it('target snapshot', () => {
 cy.visit(Cypress.env('TEST_TARGET_URL'));
 cy.matchImage({ title, preventTitleClashes: false });
 });
 it('source snapshot', () => {
 cy.visit(Cypress.env('TEST_SOURCE_URL'));
 cy.matchImage({ title, preventTitleClashes: false });
 });
});

2. .matchImage() could return image details (like path) and that could be passed as matchAgainst option. Your test would look like this:

describe('Compare', () => {
 it('target snapshot', () => {
 cy.visit(Cypress.env('TEST_TARGET_URL'));
 cy.matchImage()
 .then(image => {
 cy.visit(Cypress.env('TEST_SOURCE_URL'));
 cy.matchImage({ matchAgainst: image.path });
 });
 });
});

Which of these APIs would fit better for your usecase @notdotscott? Personally I'm more for the 2nd option as it seems to be a bit more flexible in other use-cases - any valid screenshot path could be passed to the matchAgainst.

Hi @FRSgit, thanks very much for the reply! I agree, the second option definitely looks more flexible, and is more declarative than the first, so that one gets my vote 👍

@notdotscott - I've just published an alpha version containing this feature (Go released under @frsource/cypress-plugin-visual-regression-diff@3.0.0-alpha.1--match-against). Can you give it a try?

If you have any feedback (that it works or not 😄) write it down in #146 please 🙏
Example usage can be seen here.

Hey, I've released the matchAgainst functionality in the new release - 3.0.0! 🎉
Please open a ticket if you find any issues 🙂