validate inputs to "cy" commands better

[bahmutov]

Cypress 3.1.3 on Mac

I have discovered this bad behavior while renaming cy.contains(selector, text) to cy.get(...) and leaving two strings there accidentally

bug

Try passing invalid arguments to cy.get, for example two strings and you will get error like TypeError: Cannot read property 'set' of undefined without any explanation.

Example spec file

it('calls cy get with 2 strings', () => {
  // TypeError: Cannot read property 'set' of undefined
  cy.get('.foo', 'bar')
})
it('calls cy get with string and number', () => {
  // TypeError: Cannot read property 'set' of undefined
  cy.get('.foo', 42)
})
it('calls cy get with string and a function', () => {
  // works (no warnings)
  cy.get('.foo', () => {})
})
it('calls cy get with string and empty object', () => {
  // works
  cy.get('.foo', {})
})

Here is screenshot of Cypress 3.1.3 running these tests

The first two tests should fail, but keep spinning on GET command. They fail with cryptic error message. The first test passes function instead of options object and does not complain, which is also weird. The last test fails correctly.

I have placed this spec into branch get-args at https://github.com/cypress-io/cypress-test-tiny/tree/get-args

What should happen

Each command should validate the inputs at runtime and assert that the arguments are of expected type at runtime. I suggest using check-more-types and lazy-ass to generate meaningful user-friendly errors if the user passes incorrect arguments to each cy command.

[jennifer-shehane]

These last 2 use cases you mention are actually not showing the 'Cannot read property 'set' of undefined` error. It's accurately erroring that it cannot find the element.

So, the only failures here are these, which are still present in version 3.4.0.

it('calls cy get with 2 strings', () => {
  // TypeError: Cannot read property 'set' of undefined
  cy.get('input', 'bar')
})
it('calls cy get with string and number', () => {
  // TypeError: Cannot read property 'set' of undefined
  cy.get('input', 42)
})

Notably, if you have TypeScript set up on your project, you will get warnings for things like this.

Contributing

The code for the cy.get() command is here: https://github.com/cypress-io/cypress/blob/cli-started-cypress-1573-fix/packages/driver/src/cy/commands/querying.coffee#L69

[cypress-bot]

The code for this is done in cypress-io/cypress#5174, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 3.5.0.