Every new promo rule costs us two files and a copy-paste

Problem Description

features/promo.feature covers one accepted code and four rejection cases. The four rejections are the same three lines each time; only the code that goes in and the message that comes out differ. Each of them also has its own step definition in features/step_definitions/promo.steps.js, which is where the real cost shows up - I enter an expired code, I enter an unknown code, I enter nothing, I enter a code from another region, one function each, all of them one line.

Backend shipped a fifth rejection last week: a code that has already been redeemed comes back with "This code has already been used". src/promos.js knows about it (USEDONCE); the spec does not. Nobody wants to add the sixth copy of the same three lines plus another single-line function, so it has been sitting untested for a week.

Support reads this file in sprint review, so it has to stay readable to someone who does not write JavaScript.

Output Specification

Rework features/promo.feature and features/step_definitions/promo.steps.js so that:

1. The rejection cases are expressed once, with the code that goes in and the message that comes out listed as data alongside it. Someone adding the seventh rejection next month must be able to do it by adding one line to the feature file and touching no JavaScript at all.
2. The already-used case (USEDONCE, "This code has already been used") is covered.
3. The accepted-code case keeps its own scenario - it asserts a different outcome and must not be folded in with a blank message.
4. The five single-purpose When definitions are gone.
5. src/promos.js must not change, and the step sentences must stay in the language support already reads - no element ids, URLs, or function names in the feature file.

Input Files

Extract the following files before beginning.

=============== FILE: features/promo.feature =============== Feature: Promo code validation

Scenario: A valid code is accepted Given a cart worth $40.00 When I enter a welcome code Then the promo is accepted

Scenario: An expired code is refused Given a cart worth $40.00 When I enter an expired code Then I see the message "This code has expired"

Scenario: An unknown code is refused Given a cart worth $40.00 When I enter an unknown code Then I see the message "Code not found"

Scenario: An empty code is refused Given a cart worth $40.00 When I enter nothing Then I see the message "Please enter a code"

Scenario: A code issued for another region is refused Given a cart worth $40.00 When I enter a code from another region Then I see the message "This code is not valid in your region"

=============== FILE: features/step_definitions/promo.steps.js =============== const assert = require('node:assert'); const { Given, When, Then } = require('@cucumber/cucumber'); const { validate } = require('../../src/promos');

Given('a cart worth ${float}', function (amount) { this.cartTotal = amount; });

When('I enter a welcome code', function () { this.result = validate('WELCOME10'); });

When('I enter an expired code', function () { this.result = validate('EXPIRED50'); });

When('I enter an unknown code', function () { this.result = validate('NOTREAL'); });

When('I enter nothing', function () { this.result = validate(''); });

When('I enter a code from another region', function () { this.result = validate('REGION5'); });

Then('the promo is accepted', function () { assert.strictEqual(this.result.valid, true); });

Then('I see the message {string}', function (message) { assert.strictEqual(this.result.valid, false); assert.strictEqual(this.result.message, message); });

=============== FILE: src/promos.js =============== const CODES = { WELCOME10: { valid: true }, EXPIRED50: { valid: false, message: 'This code has expired' }, REGION5: { valid: false, message: 'This code is not valid in your region' }, USEDONCE: { valid: false, message: 'This code has already been used' }, };

function validate(code) { if (code === '') return { valid: false, message: 'Please enter a code' }; const known = CODES[code]; if (!known) return { valid: false, message: 'Code not found' }; return known; }

module.exports = { validate };

=============== FILE: cucumber.js =============== module.exports = { default: { require: ['features/step_definitions/**/*.js'], format: ['progress'], }, };

=============== FILE: package.json =============== { "name": "promo-specs", "private": true, "scripts": { "bdd": "cucumber-js" }, "devDependencies": { "@cucumber/cucumber": "^10.9.0" } }