Fixtures Generator

This project was created to solve the most common problems with fixtures that we faced while building tests at VoxFeed.

Objetives

• Let each test to have its own fixtures, to prevent sharing fixtures across the tests suites.
• Specify a schema for each fixture. To make sure everyone still valid.
• Customize fixtures as required by each test.
• Make easier to find tests with invalid fixtures. Just update the schema an find all broken fixtures.

Install

Use npm or yarn:

npm install -D fixtures-generator

yarn add -D fixtures-generator

Usage

1. Declare the schemas you need
2. Import the module and build a generator
3. Use the generator to create fixtures

1. Declare the schemas you need

• Schemas are declared using JSON Schema specification.
• Schemas need to be exported as a plain object, where:
  • Object keys are the names of the schemas, this is how you will tell the generator which schema to use.
  • Object values are the schema objects.
• It is recommended to keep each schema in a separated file and join them in an index.

Example of schemas object (./schemas.js):

const authorSchema = {
  type: 'object',
  properties: {
    id: { type: 'integer' },
    name: { type: 'string' }
  }
};

const bookSchema = {
  type: 'object',
  properties: {
    id: { type: 'integer' },
    authorId: { type: 'integer' },
    title: { type: 'string' }
  }
};

const schemas = {
  author: authorSchema,
  book: bookSchema
};

module.exports = schemas;

2. Import the module and build a generator

After schemas are declared you should build a generator instance. This instance is the one you can use across your tests to generate fixtures.

Example (./generate-fixtures.js)

const FixtureGenerator = require('fixtures-generator');
const schemas = require('./schemas');

const options = {
  optionalsProbability: 0.5
};

const generateFixtures = new FixtureGenerator(schemas, options);

module.exports = generateFixtures;

Available options are:

| Option | Type | Description | | ------ | ---- | ----------- | |optionalsProbability|Float|Number between 0 and 1 that specifies the percentage of non-required propoerties that will be included in randomly generated fixtures.|

3. Use the generator to create fixtures

Finally, import the fixtures generator instance and create some fixtures.

Example:

const generateFixtures = require('./generate-fixtures');

const params = {
  type: 'author',
  quantity: 3
};

const authors = generateFixtures(params); // Will generate 3 author fixtures.

Required parameters for generateFixtures method are:

| Parameter | Type | Description | | --------- | ---- | ----------- | |type|String|The name of the fixture schema to be used to generate and validate fixture.| |recipe|[Object]|The seed of the fixtures to be generated on the same order. Resulting fixtures will keep all properties sent here.| |quantity|Number|Quantity of fixtures to be generated. If quantity is higher than the size of recipe the exceeding fixtures will be randomly generated; otherwise parameter is omitted.|

It is possible to create random fixtures by just specifying the required quantity:

const fixtures = generateFixtures('invite', 3);

// Result:
[
  {
    _id: ObjectId('592f0dabfcf681e3d5ceeb6c'),
    otherProperties...
  },
  {
    _id: ObjectId('592f0dabfcf681e3d7defb9a'),
    otherProperties...
  },
  {
    _id: ObjectId('592f0dabfcf681e3d14cab00'),
    otherProperties...
  }
];

Also, it is possible to specify an objects array that will be part of generated fixtures.

const recipe = [
  {
    campaign: ObjectId('ffffffffffffffffffffffff'),
    username: 'manuel'
  },
  {
    _id: ObjectId('a1a1a1a1a1a1a1a1a1a1a1a1')
  }
];

const fixtures = generateFixtures('invite', recipe);

// Result:
[
  {
    _id: ObjectId('592f0dabfcf681e3d5ceeb69'),
    campaign: ObjectId('ffffffffffffffffffffffff'),
    username: 'manuel',
    otherProperties...
  },
  {
    _id: ObjectId('a1a1a1a1a1a1a1a1a1a1a1a1'),
    campaign: ObjectId('39583dabfcf681e3d5ceeb61'),
    username: 'whatever',
    otherProperties...
  }
];

Schemas validation

When a recipe is used to generate fixtures, all passed properties must be valid; otherwise an error is thrown.

const recipe = [
  {
    oldProperty: 'lalala, I am a property that should not exist',
  }
];

const fixtures = generateFixtures('invite', recipe);

// It will throw an error since "oldProperty" is not a valida property for "invite" type.

⚠️ In order make this module flexible, validation is only at keys level. That means, data types are NOT validated (for example: if property username is declared as string, it won't throw error if an integer is sent in recipe). It is developer's responsibility to send the correct data type.