Proposal: .pipe command that is essentially a retryable .then

Proposal: Command that is essentially a retryable .then

Example:

const getTable = id => cy.get(`[data-testid=${id}`)
const getColumnNames = $el => Array.from($el.find('[role=columnheader]')).map(el => el.innerText)

getTable('identifier')
  .then(getColumnNames) // The `should` doesn't cause this to re-evaluate
  .should('deep.equal', ['Column One', 'Column Two'])

The getTable will get an element given a test id and getColumnNames will get the text contents of a table’s column headers. If the table’s column headers aren’t statically known (maybe column order is a user preference), the assertion immediately fails.

I don’t think we want .then to retry. I think it is good that .then has strong guarantees that it will only be run once. It just makes composition of functions not quite fit.

There could be another command that does re-run if there is an assertion:

getTable('identifier')
  .pipe(getColumnNames) // The `should` would cause re-evaluation
  .should('deep.equal', ['Column One', 'Column Two'])

[bahmutov]

You know - you work and then this guy comes in like it’s Christmas and just drops presents! Love it

Sent from my iPhone

On Oct 24, 2018, at 00:54, Nicholas Boll [e-mail] wrote:

I’ve updated cypress-pipe after adding some nice features for debugging: https://github.com/NicholasBoll/cypress-pipe

Highlights:

Basically a drop-in for .then to chain helper functions together Adds helper function name to the command log to help map test code to command log output For functions containing Cypress commands Adds before and after DOM snapshots, similar to “action” style commands like cy.click() Adds Element highlights for before and after snapshots For pure functions (no Cypress commands) retries until there is no error if an element list is returned, it will retry until the list is not empty if .pipe is chained by a should, the assertion will retry until condition is met or times out adds a DOM snapshot if either passed in subject or returned value is an Element We’ve been using it for a while on our large SPA and it really helps compose functionality. It has helped both writing tests, but also debugging them when something goes wrong.

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[NicholasBoll]

I will add a PR to the plugins and close this PR. pipe can be fully implemented in user space.

If later the Cypress team thinks it is valuable enough, pipe could be integrated into the core.

Thanks for the feedback!