cucumber-expressions

What is cucumber-expressions?

The cucumber-expressions npm package is used to define and match text patterns in Cucumber step definitions. It allows for more readable and maintainable test scenarios by using expressions to capture parameters from natural language steps.

What are cucumber-expressions's main functionalities?

Defining Cucumber Expressions

This feature allows you to define Cucumber expressions that can capture parameters from natural language steps. In this example, the expression 'I have {int} cukes' captures the integer value from the step 'I have 42 cukes'.

const { CucumberExpression, ParameterTypeRegistry } = require('cucumber-expressions');

const parameterTypeRegistry = new ParameterTypeRegistry();
const expression = new CucumberExpression('I have {int} cukes', parameterTypeRegistry);
const value = expression.match('I have 42 cukes')[0].getValue();
console.log(value); // 42

Custom Parameter Types

This feature allows you to define custom parameter types for more complex matching. In this example, a custom parameter type 'color' is defined to match the words 'red', 'blue', or 'green'.

const { ParameterTypeRegistry, ParameterType } = require('cucumber-expressions');

const parameterTypeRegistry = new ParameterTypeRegistry();
parameterTypeRegistry.defineParameterType(new ParameterType('color', /red|blue|green/, String, s => s));
const expression = new CucumberExpression('I have a {color} ball', parameterTypeRegistry);
const value = expression.match('I have a red ball')[0].getValue();
console.log(value); // 'red'

Regular Expressions

This feature allows you to use regular expressions to capture parameters from steps. In this example, the regular expression /I have (\d+) cukes/ captures the integer value from the step 'I have 42 cukes'.

const { RegularExpression, ParameterTypeRegistry } = require('cucumber-expressions');

const parameterTypeRegistry = new ParameterTypeRegistry();
const expression = new RegularExpression(/I have (\d+) cukes/, parameterTypeRegistry);
const value = expression.match('I have 42 cukes')[0].getValue();
console.log(value); // 42

Other packages similar to cucumber-expressions

gherkin

The gherkin package is used to parse Gherkin language files, which are used in Cucumber for writing test scenarios in a natural language format. While gherkin focuses on parsing feature files, cucumber-expressions focuses on matching step definitions.

regex

The regex package provides regular expression matching capabilities. While it can be used to match patterns in text, it does not provide the same level of integration with Cucumber step definitions as cucumber-expressions does.

xregexp

The xregexp package extends JavaScript's regular expression capabilities with additional features and syntax. Similar to regex, it can be used for pattern matching but does not offer the same specialized functionality for Cucumber step definitions as cucumber-expressions.

README

Cucumber Expressions for JavaScript

The docs are here.