What Is This?

This package contains a Cypress command called evalMacros that makes it easier to write tests for web applications whose test data is generated dynamically. By binding API responses to cypress @ aliases, you can refer to dynamic data when verifying the contents of the DOM. For example, if the logged-in user is bound to the @user alias, you could check for a greeting:

cy.evalMacros('Hello, {@user.firstName}')
  .then(greeting => cy.contains('.header div', greeting))

The @ is optional when referring to a Cypress alias; in the example above, {user.firstName} would yield the same result.

Macro Variables

In addition to Cypress aliases, this package supports a system of lightweight macro variables for values that don't need the full power of Cypress aliases (asynchrony, rebinding, etc). Macro variables begin with a $ to distinguish them from Cypress variables:

cy.evalMacros('I last saw {@user.nickname} on {$today.dayOfWeek}).then(
  seen => cy.contains(seen)
)

The $ is mandatory when referencing a macro variable in order to distinguish them from Cypress aliases.

Macro variables are good for values such as "today's date" that vary between test runs but are known before the tests begin executing. You can register as many variables as you want, and you decide how long the variables remain in scope by calling a reset function at the appropriate time.

If your variables are expected to change between test cases, we strongly suggest that you hook the Cypress test:before:run event to reset the variables before every test case (see sample code below). The default behavior is to instantiate them the first time evalMacros is called and never to reset them, which makes them act more like constants than variables.

Setup

Add Custom Command

In cypress/support/commands.js, add the custom commands:

import { commands as macros } from 'cypress-macros';

macros.add()

You can rename the custom command to something different if desired, or even overwrite the contains built-in command so that it automatically interpolates macro expressions.

Add Macro Variables

If you want to use macro variables in addition to Cypress variables, we recommend that you create a cypress/support/variables.js to define macro variables and install a required Cypress event hook.

import { variables } from 'cypress-macros';

// Optional: recompute all variables before every test case to avoid
// stale values.
Cypress.on("test:before:run", () => {
  variables.reset();
});

variables.add("$today", () => {
  return {
    dayOfWeek: new Date().getDay(),
    year: new Date().getFullYear()
  };
});

Don't forget to import "./variables" in cypress/support/index.js!

Cucumber Parameter Type

If you are using cypress-cucumber-preprocessor, you can define a custom parameter type that allows you to use a macro as a placeholder in a step definition.

In a step definition file named _setup.js (so it runs first), place the following code:

import {canonicalize} from 'cypress-macros/parser'

defineParameterType({
 name: "macro",
 regexp: /\{(.*)\}/,
 transformer: s => canonicalize(s) 
})

Because macros are evaluated asynchronously, you will still need to evaluate the macro in each step definition where it is used by calling evalMacros on your step parameters, but the use of curly braces allows for some nice syntactic sugar in your Cucumber features:

When I click the link {@user.nickname}

This avoids the excessive puncutation that would result if you used a {string} to capture macro expressions (When I do "{@foo}").