step_definitions.md

Step Definitions

Step definitions (Given, When, Then) are the glue between features written in Gherkin and the actual tests implementation.

Cucumber supports two types of expressions:

• Cucumber expressions
• Regular expressions

Cucumber expressions

Full docs.

Gherkin:

Given I have 42 cucumbers in my belly

JS:

import { Given } from '@cucumber/cucumber';

Given('I have {int} cucumbers in my belly', function (cucumberCount) {
  assert.equal(this.responseStatus, cucumberCount)
});

Note that your step definition functions cannot reference the world as this if you use arrow functions. See FAQ for details.

Regular expressions

Matching groups in the regular expression are passed as parameters to the step definition.

const { Then, When } = require('@cucumber/cucumber');
const assert = require('assert');
const fs = require('fs');
const mzFs = require('mz/fs')
const seleniumWebdriver = require('selenium-webdriver');

// Synchronous
Then(/^the response status is (.*)$/, function (status) {
  assert.equal(this.responseStatus, status)
});

// Asynchronous - callback
//
// Take a callback as an additional argument to execute when the step is done
Then(/^the file named (.*) is empty$/, function (fileName, callback) {
  fs.readFile(fileName, 'utf8', function(error, contents) {
    if (error) {
      callback(error);
    } else {
      assert.equal(contents, '');
      callback();
    }
  });
});

// Asynchronous - promise
//
// Return a promise. The step is done when the promise resolves or rejects
When(/^I view my profile$/, function () {
  // Assuming this.driver is a selenium webdriver
  return this.driver.findElement({ css: '.profile-link' }).then(function(element) {
    return element.click();
  });
});

Definition function wrapper

If you would like to wrap step or hook definitions in with some additional logic you can use setDefinitionFunctionWrapper(fn). The definitions will be wrapped after they have all been loaded but before the tests begin to run. One example usage is wrapping generator functions to return promises. Cucumber will do an additional stage of wrapping to ensure the function retains its original length.

// features/step_definitions/file_steps.js
const { Then } = require('@cucumber/cucumber');
const assert = require('assert');
const mzFs = require('mz/fs');

Then(/^the file named (.*) is empty$/, function *(fileName) {
  contents = yield mzFs.readFile(fileName, 'utf8');
  assert.equal(contents, '');
});

// features/support/setup.js
const { setDefinitionFunctionWrapper } = require('@cucumber/cucumber');
const isGenerator = require('is-generator');
const Promise = require('bluebird');

setDefinitionFunctionWrapper(function (fn) {
  if (isGenerator.fn(fn)) {
    return Promise.coroutine(fn);
  } else {
    return fn;
  }
});

Pending steps

Each interface has its own way of marking a step as pending

• synchronous - return 'pending'
• asynchronous callback - execute the callback with null, 'pending'
• asynchronous promise - promise resolves to 'pending'

Skipped steps

Marking a step as skipped will also mark the proceeding steps of the same scenario as skipped.

This can be used to mark a scenario as skipped based on a runtime condition.

Each interface has its own way of marking a step as skipped

• synchronous - return 'skipped'
• asynchronous callback - execute the callback with null, 'skipped'
• asynchronous promise - promise resolves to 'skipped'