TypeScript Mock Data

Package name	Weekly Downloads	Version	License	Updated
graphql-codegen-typescript-mock-data				Sep 20th, 2024

Installation

npm i -D graphql-codegen-typescript-mock-data

pnpm add -D graphql-codegen-typescript-mock-data

yarn add --dev graphql-codegen-typescript-mock-data

bun add --dev graphql-codegen-typescript-mock-data

graphql-codegen-typescript-mock-data

Description

GraphQL Codegen Plugin for building mock data based on the schema.

Installation

yarn add -D graphql-codegen-typescript-mock-data

Configuration

typesFile (string, defaultValue: null)

Defines the file path containing all GraphQL types. This file can also be generated through graphql-codegen

useTypeImports(boolean, defaultValue: false)

Will use import type rather than import when importing only types. This gives compatibility with TypeScript’s “importsNotUsedAsValues”: “error” option

addTypename (boolean, defaultValue: false)

Adds __typename property to mock data

enumsAsTypes (boolean, defaultValue: false)

Changes enums to TypeScript string union types

terminateCircularRelationships (boolean | 'immediate', defaultValue: false)

When enabled, prevents circular relationships from triggering infinite recursion. After the first resolution of a specific type in a particular call stack, subsequent resolutions will return an empty object cast to the correct type.

When enabled with immediate, it will only resolve the relationship once, independently of the call stack. Use this option if you’re experiencing out of memory errors while generating mocks.

prefix (string, defaultValue: a for consonants & an for vowels)

The prefix to add to the mock function name. Cannot be empty since it will clash with the associated typescript definition from @graphql-codegen/typescript

listElementCount (number, defaultValue: 1)

How many elements should be generated for lists. For example, with listElementCount: 3 a schema field names: [String!]! would generate 3 names in each mock.

enumValues (string, defaultValue: change-case-all#pascalCase)

Changes the case of the enums. The format of the converter must be a valid module#method. You can also use keep to keep all GraphQL names as-is. Available case functions in change-case-all are camelCase, capitalCase, constantCase, dotCase, headerCase, noCase, paramCase, pascalCase, pathCase, sentenceCase, snakeCase, lowerCase, localeLowerCase, lowerCaseFirst, spongeCase, titleCase, upperCase, localeUpperCase and upperCaseFirst See more

typeNames (string, defaultValue: change-case-all#pascalCase)

Changes the case of types. The format of the converter must be a valid module#method. You can also use keep to keep all GraphQL names as-is. Available case functions in change-case-all are camelCase, capitalCase, constantCase, dotCase, headerCase, noCase, paramCase, pascalCase, pathCase, sentenceCase, snakeCase, lowerCase, localeLowerCase, lowerCaseFirst, spongeCase, titleCase, upperCase, localeUpperCase and upperCaseFirst See more

scalars ({ [Scalar: string]: GeneratorOptions }, defaultValue: undefined)

Allows you to define mappings for your custom scalars. Allows you to map any GraphQL Scalar to a casual embedded generator (string or function key) with optional arguments, or a or faker generator with optional arguments

For detailed configuration options, see GeneratorOptions documentation.

Examples using casual

plugins:
  - typescript-mock-data:
      scalars:
        Date: date # gets translated to casual.date()

With arguments

plugins:
  - typescript-mock-data:
      scalars:
        Date: # gets translated to casual.date('YYYY-MM-DD')
          generator: date
          arguments: 'YYYY-MM-DD'

Examples using faker

plugins:
  - typescript-mock-data:
      scalars:
        Date: date.past # gets translated to faker.date.past()

With arguments

plugins:
  - typescript-mock-data:
      scalars:
        Date: # gets translated to faker.date.past(10)
          generator: date.past
          arguments: 10

Custom value generator

plugins:
  - add: "import { arrayBufferGenerator } from '../generators';"
  - typescript-mock-data:
      scalars:
        ArrayBuffer: arrayBufferGenerator()

typesPrefix (string, defaultValue: ”)

Useful if you have globally exported types under a certain namespace. e.g If the types file is something like this

declare namespace Api {
 type User {
  ...
 }
}

Setting the typesPrefix to Api. will create the following mock data

export const aUser = (overrides?: Partial<Api.User>): Api.User => {

enumsPrefix (string, defaultValue: ”)

Similar to typesPrefix, but for enum types

declare namespace Api {
 enum Status {
  ...
 }
}

Setting the enumsPrefix to Api. will create the following mock data

export const aUser = (overrides?: Partial<User>): User => {
   status: overrides && overrides.hasOwnProperty('status') ? overrides.status! : Api.Status.Online,
}

typeNamesMapping ({ [typeName: string]: string }, defaultValue: {})

Allows you to define mappings to rename the types. This is useful when you want to override the generated type name. For example, if you have a type called User and you want to rename it to RenamedUser you can do the following:

plugins:
  - typescript-mock-data:
      typesFile: '../generated-types.ts'
      typeNamesMapping:
        User: RenamedUser

This will generate the following mock function:

export const aUser = (overrides?: Partial<RenamedUser>): RenamedUser => {

Note: It is not possible to rename your enums using this option.

transformUnderscore (boolean, defaultValue: true)

When disabled, underscores will be retained for type names when the case is changed. It has no effect if typeNames is set to keep.

dynamicValues (boolean, defaultValue: false)

When enabled, values will be generated dynamically when the mock function is called rather than statically when the mock function is generated. The values are generated consistently from a casual seed that can be manually configured using the generated seedMocks(seed: number) function, as shown in this test.

useImplementingTypes (boolean, defaultValue: false)

When enabled, it will support the useImplementingTypes GraphQL codegen configuration.

• When a GraphQL interface is used for a field, this flag will use the implementing types, instead of the interface itself.

defaultNullableToNull (boolean, defaultValue: false)

When enabled, it will set all nullable fields to null per default instead of generating a value.

fieldGeneration ({ [typeName: string]: { [fieldName: string]: GeneratorOptions } }, defaultValue: undefined)

This setting allows you to add specific generation to a field for a given type. For example if you have a type called User and a field called birthDate you can override any generated value there as follows:

plugins:
  - typescript-mock-data:
      scalars:
        Date: date.future
      fieldGeneration:
        User:
          birthDate: date.past

Note that even if birthDate is a scalar of Date type, its value will still be overridden.

If you want to use a specific generator for all fields of a given name, you can declare it under a property called _all:

plugins:
  - typescript-mock-data:
      scalars:
        Date: date.future
      fieldGeneration:
        _all:
          email: internet.email
        AdminUser:
          email: 'admin@email.com'

In the above example all resolvers with the name email will use the internet.email generator. However since we specified a specific email for AdminUser that will take precedence over the _all generated value.

For detailed configuration options, see GeneratorOptions documentation.

generateLibrary ('casual' | 'faker', defaultValue: 'faker')

Select a library to generate mock values. The default is faker, Other options include casual casual is not maintained and will be remove in future major versions. faker is useful when you want to use a mock function with the dynamicValues option enabled in the browser.

GeneratorOptions type

This type is used in scalars and fieldGeneration options.

Examples using faker

With arguments

plugins:
  - typescript-mock-data:
      scalars:
        Date: # gets translated to faker.date.past(10)
          generator: date.past
          arguments: 10

With multiple arguments

plugins:
  - typescript-mock-data:
      scalars:
        Description: # gets translated to faker.lorem.paragraphs(3, '\n')
          generator: lorem.paragraphs
          arguments:
            - 3
            - '\n'

Shorthand if you don’t have arguments

plugins:
  - typescript-mock-data:
      scalars:
        Date: date.past # gets translated to faker.date.past()

With extra function call

fieldName: # gets translated to faker.date.past().toLocaleDateString()
  generator: date.past
  extra:
    function: toLocaleDateString

With extra function call arguments

fieldName: # gets translated to faker.date.past().toLocaleDateString('en_GB)
  generator: date.past
  extra:
    function: toLocaleDateString
    arguments: 'en_GB'

Custom value generator

# gets translated as is
fieldName: arrayBufferGenerator()

Examples using casual (deprecated)

Shorthand if you don’t have arguments

fieldName: date # gets translated to casual.date()

With arguments

fieldName: # gets translated to casual.date('YYYY-MM-DD')
  generator: date
  arguments: 'YYYY-MM-DD'

With multiple arguments

fieldName: # gets translated to casual.integer(-100, 100)
  generator: integer
  arguments:
    - -100
    - 100

With extra function call

fieldName: # gets translated to casual.integer.toFixed()
  generator: integer
  extra:
    function: toFixed

With extra function call arguments

fieldName: # gets translated to casual.integer.toFixed(3)
  generator: integer
  extra:
    function: toFixed
    arguments: 3

Examples of usage

codegen.yml

overwrite: true
schema: schema.graphql
generates:
  src/generated-types.ts:
    plugins:
      - 'typescript'
  src/mocks/generated-mocks.ts:
    plugins:
      - typescript-mock-data:
          typesFile: '../generated-types.ts'
          enumValues: upper-case#upperCase
          typeNames: keep
          scalars:
            AWSTimestamp: number.int # gets translated to faker.number.int()

With eslint-disable rule

codegen.yml

overwrite: true
schema: schema.graphql
generates:
  src/generated-types.ts:
    plugins:
      - 'typescript'
  src/mocks/generated-mocks.ts:
    plugins:
      - add:
          content: '/* eslint-disable @typescript-eslint/no-use-before-define,@typescript-eslint/no-unused-vars,no-prototype-builtins */'
      - typescript-mock-data:
          typesFile: '../generated-types.ts'
          enumValues: upper-case#upperCase
          typeNames: keep
          scalars:
            AWSTimestamp: number.int # gets translated to faker.number.int()

Example of generated code

Given the following schema:

scalar AWSTimestamp
 
type Avatar {
  id: ID!
  url: String!
}
 
type User {
  id: ID!
  login: String!
  avatar: Avatar
  status: Status!
  updatedAt: AWSTimestamp
}
 
type Query {
  user: User!
}
 
input UpdateUserInput {
  id: ID!
  login: String
  avatar: Avatar
}
 
enum Status {
  ONLINE
  OFFLINE
}
 
type Mutation {
  updateUser(user: UpdateUserInput): User
}

The code generated will look like:

export const anAvatar = (overrides?: Partial<Avatar>): Avatar => {
  return {
    id: overrides && overrides.hasOwnProperty('id') ? overrides.id! : '0550ff93-dd31-49b4-8c38-ff1cb68bdc38',
    url: overrides && overrides.hasOwnProperty('url') ? overrides.url! : 'aliquid',
  };
};
 
export const anUpdateUserInput = (overrides?: Partial<UpdateUserInput>): UpdateUserInput => {
  return {
    id: overrides && overrides.hasOwnProperty('id') ? overrides.id! : '1d6a9360-c92b-4660-8e5f-04155047bddc',
    login: overrides && overrides.hasOwnProperty('login') ? overrides.login! : 'qui',
    avatar: overrides && overrides.hasOwnProperty('avatar') ? overrides.avatar! : anAvatar(),
  };
};
 
export const aUser = (overrides?: Partial<User>): User => {
  return {
    id: overrides && overrides.hasOwnProperty('id') ? overrides.id! : 'a5756f00-41a6-422a-8a7d-d13ee6a63750',
    login: overrides && overrides.hasOwnProperty('login') ? overrides.login! : 'libero',
    avatar: overrides && overrides.hasOwnProperty('avatar') ? overrides.avatar! : anAvatar(),
    status: overrides && overrides.hasOwnProperty('status') ? overrides.status! : Status.Online,
    updatedAt: overrides && overrides.hasOwnProperty('updatedAt') ? overrides.updatedAt! : 1458071232,
  };
};

Usage in tests

Those helper functions can be used in our unit tests:

const user = aUser({ login: 'johndoe' });
 
// will create a user object with `login` property overridden to `johndoe`

Dealing with Timezone

If some properties use generated dates, the result could different depending on the timezone of your machine.

To force a timezone, you can set environment variable TZ:

TZ=UTC graphql-codegen

This will force the timezone to UTC, whatever the timezone of your machine or CI

Contributing

Feel free to open issues and pull requests. We always welcome support from the community.

To run this project locally:

• Use Node >= 16
• Make sure that you have the latest Yarn version (https://yarnpkg.com/lang/en/docs/install/)
• Clone this repo using git clone
• Run yarn
• Run yarn build to build the package
• Run yarn test to make sure everything works

License

MIT