@anatine/zod-mock

Generates a mock data object using faker.js from a Zod schema.

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Installation

@faker-js/faker is a peer dependency of @anatine/zod-mock and is used for mock data generation.

1npm install zod @faker-js/faker @anatine/zod-mock

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Usage

Take any Zod schema and create mock data

1import { generateMock } from '@anatine/zod-mock';
2const schema = z.object({
3      uid: z.string().nonempty(),
4      theme: z.enum([`light`, `dark`]),
5      email: z.string().email().optional(),
6      phoneNumber: z.string().min(10).optional(),
7      avatar: z.string().url().optional(),
8      jobTitle: z.string().optional(),
9      otherUserEmails: z.array(z.string().email()),
10      stringArrays: z.array(z.string()),
11      stringLength: z.string().transform((val) => val.length),
12      numberCount: z.number().transform((item) => `total value = ${item}`),
13      age: z.number().min(18).max(120),
14    });
15const mockData = generateMock(schema);
16// ...

This will generate mock data similar to:

1{
2  "uid": "3f46b40e-95ed-43d0-9165-0b8730de8d14",
3  "theme": "light",
4  "email": "Alexandre99@hotmail.com",
5  "phoneNumber": "1-665-405-2226",
6  "avatar": "https://cdn.fakercloud.com/avatars/olaolusoga_128.jpg",
7  "jobTitle": "Lead Brand Facilitator",
8  "otherUserEmails": [
9    "Wyman58@example.net",
10    "Ignacio_Nader@example.org",
11    "Jorge_Bradtke@example.org",
12    "Elena.Torphy33@example.org",
13    "Kelli_Bartoletti@example.com"
14  ],
15  "stringArrays": [
16    "quisquam",
17    "corrupti",
18    "atque",
19    "sunt",
20    "voluptatem"
21  ],
22  "stringLength": 4,
23  "numberCount": "total value = 25430",
24  "age": 110
25}

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Overriding string mocks

Sometimes there might be a reason to have a more specific mock for a string value.

You can supply an options field to generate specific mock data that will be triggered by the matching key.

1const schema = z.object({
2  locked: z.string(),
3  email: z.string().email(),
4  primaryColor: z.string(),
5});
6const mockData = generateMock(schema, {
7  stringMap: {
8    locked: () => `this return set to the locked value`,
9    email: () => `not a email anymore`,
10    primaryColor: () => faker.internet.color(),
11  },
12});

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Adding a seed generator

For consistent testing, you can also add in a seed or seed array.

1const schema = z.object({
2  name: z.string(),
3  age: z.number(),
4});
5const seed = 123;
6const first = generateMock(schema, { seed });
7const second = generateMock(schema, { seed });
8expect(first).toEqual(second);

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Adding a custom mock mapper

Once drilled down to deliver a string, number, boolean, or other primitive value a function with a matching name is searched for in faker.

You can add your own key/fn mapper in the options.

1
2export function mockeryMapper(
3  keyName: string,
4  fakerInstance: Faker
5): FakerFunction | undefined {
6  const keyToFnMap: Record<string, FakerFunction> = {
7    image: fakerInstance.image.url,
8    imageurl: fakerInstance.image.url,
9    number: fakerInstance.number.int,
10    float: fakerInstance.number.float,
11    hexadecimal: fakerInstance.number.hex,
12    uuid: fakerInstance.string.uuid,
13    boolean: fakerInstance.datatype.boolean,
14    // Email more guaranteed to be random for testing
15    email: () => fakerInstance.database.mongodbObjectId() + '@example.com'
16  };
17  return keyName && keyName.toLowerCase() in keyToFnMap
18    ? keyToFnMap[keyName.toLowerCase() as never]
19    : undefined;
20}
21
22const schema = z.object({
23  locked: z.string(),
24  email: z.string().email(),
25  primaryColor: z.string(),
26});
27
28const result = generateMock(schema, { mockeryMapper });
29

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Behind the Scenes

zod-mock tries to generate mock data from two sources.

• Object key name ie({ firstName: z.string() })

  This will check the string name of the key against all the available faker function names. Upon a match, it uses that function to generate a mock value.

• Zodtype ie(const something = z.string())

  In the case there is no key name (the schema doesn't contain an object) or there is no key name match, zod-mock will use the primitive type provided by zod.

  Some zod filter types (email, uuid, url, min, max, length) will also modify the results.

  If zod-mock does not yet support a Zod type used in your schema, you may provide a backup mock function to use for that particular type.

  1const schema = z.object({
  2  anyVal: z.any()
  3});
  4const mockData = generateMock(schema, {
  5  backupMocks: {
  6    ZodAny: () => 'a value'
  7  }
  8});

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Missing Features

• No pattern for passing options into faker, such as setting phone number formatting
• Does not handle the following Zod types:
  • ZodAny
  • ZodDefault
  • ZodFunction
  • ZodIntersection
  • ZodMap
  • ZodPromise
  • ZodSet
  • ZodTuple
  • ZodUnion
  • ZodUnknown

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Credits

• express-zod-api

  A great lib that provided some insights on dealing with various zod types.

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This library is part of a nx monorepo @anatine/zod-plugins.