The difference is between attribute and property.

Under the hood cy.getByTestId('save').should('be.disabled') is checking that the element has property disabled. The standard button translates the attribute disabled into a corresponding property, so it passes the above assertion.

The custom button obviously does not have that behavior, so it might be difficult to treat custom-button the same as button.

One thing that works for your sample is

cy.getByTestId('save').should('have.attr', 'disabled')

This should work for all occurrences of custom-button (if my assumption about it's behavior is correct).

If you have trouble with standard button, you can check both:

cy.getByTestId('save').should($el => {
  return $el.attr('disabled').length > 0 || $el.prop('disabled').length > 0
})

You can make a custom assertion if that's a pain to code everywhere.

IMO using .find('button') isn't optimal, since it's an internal implementation of the custom-button.

This solution should work:

cy.contains('01 - Parts inventory').parent().next().children()
.should('have.text','2899869.56')

Try to use another way to clear localStorage. For example, I'm using these commands to save, restore and clear storage and is working perfect. I'm using these for log in/log out things.

let LOCAL_STORAGE_MEMORY = {};

Cypress.Commands.add("saveLocalStorage", () => {
  Object.keys(localStorage).forEach(key => {
    LOCAL_STORAGE_MEMORY[key] = localStorage[key];
  });
});

Cypress.Commands.add("restoreLocalStorage", () => {
  Object.keys(LOCAL_STORAGE_MEMORY).forEach(key => {
    localStorage.setItem(key, LOCAL_STORAGE_MEMORY[key]);
  });
});

Cypress.Commands.add("clearLocalStorageCache", () => {
  localStorage.clear();
  LOCAL_STORAGE_MEMORY = {};
});

Not really less code, but gives you a stronger test:

If you use a Set you can verify the lengths of .children() and the length of the set.

The Set object lets you store unique values of any type

This does not limit you to comparing next and current, it compares across all children.

cy.get(".grid").children()
  .then($els => {
    const setOfTexts = new Set();
    [...$els].forEach(el => setOfTexts.add(el.innerText)); // only stores unique values
    return setOfTexts;
  })
  .then(setOfTexts => {
     cy.get(".grid").children().its('length')
       .should('eq', setOfTexts.size)
  })

or with a reducer,

cy.get(".grid").children()
  .then($els => [...$els].reduce((acc, el) => {
    acc.add(el.innerText)
  }, new Set()))
  .then(setOfTexts => {
     cy.get(".grid").children().its('length')
       .should('eq', setOfTexts.size)
  })

Based on my experience (sorry, it would be ideal to see the source code too), but this could be due to the element being inside an iframe. At this stage, Cypress does not seem to support elements residing inside iframe with this Github issue still open: https://github.com/cypress-io/cypress/issues/136

From a few workarounds on the link above, this resolved my issue:

Cypress.Commands.add('iframe', { prevSubject: 'element' }, $iframe => {
    return new Cypress.Promise(resolve => {
        $iframe.on('load', () => {
            resolve($iframe.contents().find('body'));
        });
    });
});
// for <iframe id="foo" src="bar.html"></iframe>
cy.get('#foo').iframe().find('.checkbox_0.0').click({ force: true });

Problem

I understand the intention of the Gatsby documentation avoid executing useStaticQuery, but the approach implicitly recommends leaving code uncovered.

Recommendation

To achieve code coverage, the most logical thing to do would be to either mock useStaticQuery or better yet use MockProvider.

GraphQL Testing: MockProvider - https://www.apollographql.com/docs/react/development-testing/testing/#mockedprovider

Your route should point to just the path, not the full URL. Try changing it to cy.route("/admin/portfolio/putstrategy").as("updatetrategy")

I'm assuming it's just a snippet from your test, but if you don't have cy.server() before you call into cy.route(), you'll need to add that as well.

If you're stubbing a response You have to write like this:

cy.intercept('GET', '**/tags', { fixture: 'tags.json' })

Well this seems to work, so it tells me I have some more to learn about .should()

cy.get('.check-box-sub-text').should('not.exist');