Convenient access to aliases values by overwriting the should command

In addition to overwriting regular Cypress commands, we can overwrite the should assertion command. For example, we can automatically look up aliased values (since they were already computed by the time we get to execute the should command). We could always look up any values that start with @ character.

📺 You can watch this recipe explained in the video Overwrite The cy.should Command To Automatically Look Up Aliased Values (opens new window).

<p>
  During the tournament, the player A got
  <span class="score">60</span> points, while the player B got
  <span class="score">81</span> points.
</p>

During the tournament, the player A got 60 points, while the player B got 81 points.

.score {
  font-weight: 700;
}

// automatically replace any string values that start with "@"
// with the aliased value, if it exists
Cypress.Commands.overwrite('should', (should, ...args) => {
  const aliases = cy.state('aliases')
  const lookedUp = args.map((a) => {
    if (typeof a === 'string' && a[0] === '@') {
      const key = a.slice(1)
      if (key in aliases) {
        return aliases[key].subjectChain[0]
      } else {
        return a
      }
    }
    return a
  })
  return should(...lookedUp)
})

Here is a simple example of looking up the "answer" alias.

cy.wrap(42).as('answer')
cy.wrap(20 + 22).should('equal', '@answer')

Now let's compare two scores we extract from the page. Automatically looking up aliased values inside the should assertions lets us avoid the pyramid of Doom and additional cy.then(function () { ... }) callbacks.

cy.get('.score')
  .first()
  .invoke('text')
  .then(parseInt)
  .as('scoreA')
cy.get('.score')
  .eq(1)
  .invoke('text')
  .then(parseInt)
  .should('be.above', '@scoreA')