Checking for duplicates

Checking the list for duplicates

<ul>
  <li>Apples</li>
  <li>Oranges</li>
  <li>Bananas</li>
</ul>

The check below reports if the array of unique elements has the same length as the original. It does not report which elements are duplicates.

// destructure Cypress._ for convenience
const { map, uniq, countBy, pickBy } = Cypress._
cy.get('li')
  // wait for the list to be stable
  .should('have.length', 3)
  .and(($list) => {
    const values = Cypress._.map($list, 'innerText')
    const distinct = uniq(values)
    expect(distinct, 'all strings are different').to.have.length(
      values.length,
    )
  })

If you need to report the duplicate elements, I suggest using Lodash countBy and pickBy functions and reporting all entries with the count larger than 1.

cy.get('li').should(($list) => {
  const counts = countBy(map($list, 'innerText'))
  const duplicates = pickBy(counts, (n) => n > 1)
  expect(duplicates, 'duplicates').to.be.empty
})

Checking for duplicate attributes

Let's say we need to compare the items by an attribute and detect any duplicates. Grab all the items and build the assertion inside the should(cb) function for retry-ability.

<ul>
  <li data-product-id="a11">Apples</li>
  <li data-product-id="b20">Oranges</li>
  <li data-product-id="c11">Bananas</li>
</ul>

// destructure Cypress._ for convenience
const { map, countBy, pickBy } = Cypress._
cy.get('li').should(($list) => {
  const ids = map($list, ($el) =>
    $el.getAttribute('data-product-id'),
  )
  const counts = countBy(ids)
  const duplicates = pickBy(counts, (n) => n > 1)
  expect(duplicates, 'duplicates').to.be.empty
})

Watch the video Detect Duplicate Attributes Using Lodash Functions And Should Callback. Also check out the recipe Find duplicates.