Cucumber-js 中的装饰步骤实现

Question

Introduction

Im using https://github.com/cucumber/cucumber-js in typescript. Sample of code implementation looks like average cucumber implementation:

import {
    Given,
    Then,
    When
} from 'cucumber'

Given(`Page is up and running`, function(this: World) {
    someFunction()
})

Goal

What I would like to achieve is to be able to somehow decorate Given , so that:

• some action can be invoked before code inside Given . Lets say, for simple example, I would like to print first Given argument (so Page is up and running ).
• there would be no need to modify existing step implementation.

Each step got two alias function definitions in index.d.ts , eg:

export function Given(pattern: RegExp | string, code: StepDefinitionCode): void;
export function Given(pattern: RegExp | string, options: StepDefinitionOptions, code: StepDefinitionCode): void;

Answer 1

In the original version of CucumberJS, there were more hooks available including beforeStep . However, there is a way to achieve this functionality in versions of the framework such as 6.0.5 using setDefinitionFunctionWrapper . Example:

setDefinitionFunctionWrapper(fn => async function step(...args) {
    //
    // do something before the step definition runs.
    //
    const result = await fn.apply(this, args);
    //
    // do something after the step definition runs.
    //
    return result;
});

Online Example: https://testjam.io/?p=O2wodDVOveAMdA9HKMKy

Known limitations and caveats :

• This function will wrap every step definition AND hook.
• This particular implementation assumes that the step definition or hook is not using a callback.
• I'm not sure how to make callbacks and promises work here at the same time, it may be possible but you'll have to manage that yourself by possibly inspecting the type of the last parameter and then handling it from there.

Update: The beforeStep and afterStep hooks are available in CucumberJS 7.x and later