TypeScript Mock Data Factory

Package name	Weekly Downloads	Version	License	Updated
`@mizdra/graphql-codegen-typescript-fabbrica`				Mar 23rd, 2024

Installation

npm i -D @mizdra/graphql-codegen-typescript-fabbrica

graphql-codegen-typescript-fabbrica

GraphQL Code Generator Plugin to define mock data factory.

Installation

npm install --save-dev @mizdra/graphql-codegen-typescript-fabbrica

Requirements


         graphql

>= 16.0.0


         typescript

>= 5.0.0


         --moduleResolution Bundler


         --moduleResolution Node16


         --moduleResolution NodeNext

is required

Playground

You can try this library in the following playground.

https://stackblitz.com/edit/playground-graphql-codegen-typescript-fabbrica?file=src%2Findex.test.ts&view=editor

Usage

First, you should configure the configuration file of GraphQL Code Generator as follows.

// codegen.ts
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      config: {
        enumsAsTypes: true, // required
        avoidOptionals: true, // required
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      config: {
        typesFile: './types', // required
        // typesFile: './types.js' // If you use factories from Node.js and set `package.json#type` to `module`, you should add `.js` extension
export default config;

# schema.graphql
type Book {
  id: ID!
  title: String!
  author: Author!
type Author {
  id: ID!
  name: String!
  books: [Book!]!
Second, you should generate the code with the GraphQL Code Generator.
npx graphql-codegen

Then, the utilities to define a factory are generated. You can define your preferred factory with it.
// src/app.ts
import { defineBookFactory, defineAuthorFactory, dynamic } from '../__generated__/fabbrica';
import { faker } from '@faker-js/faker';
const BookFactory = defineBookFactory({
  defaultFields: {
    __typename: 'Book',
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(() => faker.word.noun()),
    author: undefined,
const AuthorFactory = defineAuthorFactory({
  defaultFields: {
    __typename: 'Author',
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: dynamic(() => faker.person.firstName()),
    books: undefined,
The factory generates strictly typed mock data.
// simple
const book0 = await BookFactory.build();
expect(book0).toStrictEqual({
  __typename: 'Book',
  id: 'Book-0',
  title: expect.any(String),
  author: undefined,
expectTypeOf(book0).toEqualTypeOf<{
  __typename: 'Book';
  id: string;
  title: string;
  author: undefined;
}>();
// nested
const book1 = await BookFactory.build({
  author: await AuthorFactory.build(),
expect(book1).toStrictEqual({
  __typename: 'Book',
  id: 'Book-1',
  title: expect.any(String),
  author: {
    __typename: 'Author',
    id: 'Author-0',
    name: expect.any(String),
    books: undefined,
expectTypeOf(book1).toEqualTypeOf<{
  __typename: 'Book';
  id: string;
  title: string;
  author: {
    __typename: 'Author';
    id: string;
    name: string;
    books: undefined;
}>();





    

Notable features

The library has several notable features. And many of them are inspired by FactoryBot.
Dynamic Fields

The dynamic function allows you to define fields with a dynamic value.
import { dynamic } from '../__generated__/fabbrica';
const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(() => faker.datatype.uuid()),
    title: 'Yuyushiki',
expect(await BookFactory.build()).toStrictEqual({
  id: expect.any(String), // Randomly generated UUID
  title: 'Yuyushiki',
Sequences

Sequences allow you to build sequentially numbered data.
const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(async ({ seq }) => Promise.resolve(`Yuyushiki Vol.${seq}`)),
    author: undefined,
expect(await BookFactory.build()).toStrictEqual({
  id: 'Book-0',
  title: 'Yuyushiki Vol.0',
  author: undefined,
expect(await BookFactory.build()).toStrictEqual({
  id: 'Book-1',
  title: 'Yuyushiki Vol.1',
  author: undefined,
Dependent Fields

Fields can be based on the values of other fields using get function.
const UserFactory = defineUserFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `User-${seq}`),
    name: 'yukari',
    email: dynamic(async ({ get }) => `${(await get('name')) ?? 'defaultName'}@yuyushiki.net`),
expect(await UserFactory.build()).toStrictEqual({
  id: 'User-0',
  name: 'yukari',
  email: '[email protected]',
expect(await UserFactory.build({ name: 'yui' })).toStrictEqual({
  id: 'User-1',
  name: 'yui',
  email: '[email protected]',
Building lists

You can build a list of mock data with the buildList method.




    

const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(({ seq }) => `Yuyushiki Vol.${seq}`),
    author: undefined,
expect(await BookFactory.buildList(3)).toStrictEqual([
  { id: 'Book-0', title: 'Yuyushiki Vol.0', author: undefined },
  { id: 'Book-1', title: 'Yuyushiki Vol.1', author: undefined },
  { id: 'Book-2', title: 'Yuyushiki Vol.2', author: undefined },
Build mock data of related types (a.k.a. Associations)

You can build mock data of the relevant type in one shot.
const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(({ seq }) => `Yuyushiki Vol.${seq}`),
    author: undefined,
const AuthorFactory = defineAuthorFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: 'Komata Mikami',
    books: dynamic(async () => BookFactory.buildList(1)), // Build mock data of related types
expect(await AuthorFactory.build()).toStrictEqual({
  id: 'Author-0',
  name: 'Komata Mikami',
  books: [{ id: 'Book-0', title: 'Yuyushiki Vol.0', author: undefined }],
Transient Fields

Transient fields are only available within the factory definition and are not included in the data being built. This allows more complex logic to be used inside factories.
import { defineAuthorFactory, dynamic } from '../__generated__/fabbrica';
import { Author } from '../__generated__/types';
const AuthorFactory = defineAuthorFactory.withTransientFields({
  bookCount: 0,
  defaultFields: {
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: 'Komata Mikami',
    books: dynamic(async ({ get }) => {
      const bookCount = (await get('bookCount')) ?? 0;
      return BookFactory.buildList(bookCount);
expect(await AuthorFactory.build({ bookCount: 3 })).toStrictEqual({
  id: 'Author-0',
  name: 'Komata Mikami',
  books: [
    { id: 'Book-0', title: 'Yuyushiki Vol.0', author: undefined },
    { id: 'Book-1', title: 'Yuyushiki Vol.1', author: undefined },
    { id: 'Book-2', title: 'Yuyushiki Vol.2', author: undefined },
Additional Fields

You can add additional fields to the data being built. This is useful when you want to build a fake data for a query that contains aliases, such as:




    

query GetAuthorInfo {
  author(id: '1') {
    books {
      title
    popularBooks: books(popularOnly: true) {
      title
import { defineAuthorFactory, type OptionalAuthor, dynamic } from '../__generated__/fabbrica';
const AuthorFactory = defineAuthorFactory.withAdditionalFields<{ popularBooks: OptionalAuthor['books'] }>()({
  defaultFields: {
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: 'Komata Mikami',
    // Generate a fake data for the `Author.books()` field
    books: dynamic(() => BookFactory.buildList(3)),
    // Generate a fake data for the `Author.books(popularOnly: true)` field
    popularBooks: dynamic(() => BookFactory.buildList(1)),
expect(await AuthorFactory.build()).toStrictEqual({
  id: 'Author-0',
  name: 'Komata Mikami',
  books: [
    { id: 'Book-0', title: 'Yuyushiki Vol.0' },
    { id: 'Book-1', title: 'Yuyushiki Vol.1' },
    { id: 'Book-2', title: 'Yuyushiki Vol.2' },
  popularBooks: [{ id: 'Book-3', title: 'Yuyushiki Vol.3' }],
Traits

Traits allow you to group the default values of fields and apply them to factories.
import I_SPACER from '../assets/spacer.gif';
import I_AVATAR from '../assets/dummy/avatar.png';
import I_BANNER from '../assets/dummy/banner.png';
const ImageFactory = defineImageFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Image-${seq}`),
    url: I_SPACER.src,
    width: I_SPACER.width,
    height: I_SPACER.height,
  traits: {
    avatar: {
      defaultFields: {
        url: I_AVATAR.src,
        width: I_AVATAR.width,
        height: I_AVATAR.height,
    banner: {
      defaultFields: {
        url: I_BANNER.src,
        width: I_BANNER.width,
        height: I_BANNER.height,
expect(await ImageFactory.build()).toStrictEqual({
  id: 'Image-0',
  url: I_SPACER.src,
  width: I_SPACER.width,
  height: I_SPACER.height,
expect(await ImageFactory.use('avatar').build()).toStrictEqual({
  id: 'Image-1',
  url: I_AVATAR.src,
  width: I_AVATAR.width,
  height: I_AVATAR.height,
expect(await ImageFactory.use('banner').build()).toStrictEqual({
  id: 'Image-2',
  url: I_BANNER.src,
  width: I_BANNER.width,
  height: I_BANNER.height,
Available configs

Several configs can be set in the GraphQL Code Generator configuration file.
typesFile

type: string, required
Defines the file path containing all GraphQL types. This file can be generated with the typescript plugin.
If you use factories on Node.js and set package.json#type to module, you should add .js extension to the file path. If you use factories on other runtimes, you should not add .js extension.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      config: {
        // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      config: {
        typesFile: './types', // required
        // typesFile: './types.js' // If you use factories from Node.js and set `package.json#type` to `module`, you should add `.js` extension
skipTypename

type: boolean, default: false
Does not add __typename to the fields that can be passed to factory.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      config: {
        // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      config: {
        // ...
        skipTypename: true,
export default config;





    

skipIsAbstractType

type: boolean, default: true
Does not add __is<AbstractType> to the fields that can be passed to factory. __is<AbstractType> is a field that relay-compiler automatically adds to the query1². It is recommended for Relay users to set this option to false.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      config: {
        // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      config: {
        // ...
        skipIsAbstractType: false,
export default config;





    

nonOptionalDefaultFields

type: boolean, default: false
Make it mandatory to pass all fields to defaultFields. This is useful to force the defaultFields to be updated when new fields are added to the schema.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      config: {
        // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      config: {
        // ...
        nonOptionalDefaultFields: true,
export default config;

namingConvention

type: NamingConvention, default: change-case-all#pascalCase
Allow you to override the naming convention of the output.
This option is compatible with the one for typescript plugin. If you specify it for the typescript plugin, you must set the same value for graphql-codegen-typescript-fabbrica.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  config: {
    namingConvention: 'change-case-all#lowerCase',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      // ...
export default config;

typesPrefix

type: string, default: ''
Prefixes all the generated types.
This option is compatible with the one for typescript plugin. If you specify it for the typescript plugin, you must set the same value for graphql-codegen-typescript-fabbrica.
import { CodegenConfig } from '@graphql-codegen/cli';
const config: CodegenConfig = {
  schema: './schema.graphql',
  config: {
    typesPrefix: 'I',
  generates: {
    '__generated__/types.ts': {
      plugins: ['typescript'],
      // ...
    './__generated__/fabbrica.ts': {
      plugins: ['@mizdra/graphql-codegen-typescript-fabbrica'],
      // ...
export default config;





    

typesSuffix

type: string, default: ''
Suffixes all the generated types.
This option is compatible with the one for typescript plugin. If you specify it for the typescript plugin, you must set the same value for graphql-codegen-typescript-fabbrica.
Troubleshooting

error TS7022: '<Type>Factory' implicitly has type 'any' because ...

Creating a circular type with Associations may cause compile errors.
const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(({ seq }) => `ゆゆ式 ${seq}巻`),
    author: dynamic(({ seq }) => AuthorFactory.build()),
const AuthorFactory = defineAuthorFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: dynamic(({ seq }) => `${seq}上小又`),
    books: dynamic(({ seq }) => BookFactory.buildList()),
$ npx tsc --noEmit
example.ts:1:7 - error TS7022: 'BookFactory' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
1     const BookFactory = defineBookFactory({
            ~~~~~~~~~~~
example.ts:8:7 - error TS7022: 'AuthorFactory' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
8     const AuthorFactory = defineAuthorFactory({
            ~~~~~~~~~~~~~

This error is due to the type of each field being cycled, making the type undecidable. To avoid this, you can pass undefined to any field.
const BookFactory = defineBookFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Book-${seq}`),
    title: dynamic(({ seq }) => `ゆゆ式 ${seq}巻`),
    author: dynamic(({ seq }) => AuthorFactory.build()),
const AuthorFactory = defineAuthorFactory({
  defaultFields: {
    id: dynamic(({ seq }) => `Author-${seq}`),
    name: dynamic(({ seq }) => `${seq}上小又`),
    // Pass `undefined` to avoid type being undecidable.
    books: undefined,
error TS2307: Cannot find module '@mizdra/graphql-codegen-typescript-fabbrica/helper' or its corresponding type declarations.

Incorrect values for the moduleResolution option in tsconfig.json cause compile errors.
  "compilerOptions": {
    "moduleResolution": "node" // incorrect
$ npx tsc --noEmit
__generated__/1-basic/fabbrica.ts:7:8 - error TS2307: Cannot find module '@mizdra/graphql-codegen-typescript-fabbrica/helper' or its corresponding type declarations.
7 } from '@mizdra/graphql-codegen-typescript-fabbrica/helper';
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To resolve this error, set the value of moduleResolution to Bundler, Node16 or NodeNext.
  "compilerOptions": {
    "moduleResolution": "Bundler" // ok
License

This library is licensed under the MIT license.
The copyright contains two names. The first is @mizdra, author of graphql-codegen-typescript-fabbrica. The second is @Quramy, author of prisma-fabbrica.
The name of the author of prisma-fabbrica is written because graphql-codegen-typescript-fabbrica reuses some of prisma-fabbrica’s code.
Footnotes

https://github.com/facebook/relay/issues/3129#issuecomment-659439154 ↩

TypeScript Mock Data Factory

Installation

graphql-codegen-typescript-fabbrica

Installation

Requirements

Playground

Usage

Notable features

Dynamic Fields

Sequences

Dependent Fields

Building lists

Build mock data of related types (a.k.a. Associations)

Transient Fields

Additional Fields

Traits

Available configs

`typesFile`

`skipTypename`

`skipIsAbstractType`

`nonOptionalDefaultFields`

`namingConvention`

`typesPrefix`

`typesSuffix`

Troubleshooting

`error TS7022: '<Type>Factory' implicitly has type 'any' because ...`

`error TS2307: Cannot find module '@mizdra/graphql-codegen-typescript-fabbrica/helper' or its corresponding type declarations.`

License

Footnotes