@reflow-work/test-fixture-factory

Create test fixtures easily!

This library is inspired by Ecto Test factories.

Install

npm install --save-dev @reflow-work/test-fixture-factory

Usage

1import { FixtureFactory } from '@reflow-work/test-fixture-factory';
2
3type UserType = {
4  name: string;
5  age: number;
6};
7
8const userFactory = new FixtureFactory<UserType>(() => {
9  return { name: 'name', age: 30 };
10});
11
12// creating a user
13const user0 = userFactory.create();
14
15// { name: 'name', age: 30 }
16
17// creating a user with overriding attributes
18const user1 = userFactory.create({ name: 'new name' });
19
20// { name: 'new name', age: 30 }
21
22// creating users
23const [user2, user3] = userFactory.createList(2);
24
25// [{ name: 'name', age: 30 }, { name: 'name', age: 30 }]
26
27// creating users with overriding attributes
28const [user4, user5] = userFactory.createList(2, [
29  { name: 'new name' },
30  { age: 40 },
31]);
32
33// [{ name: 'new name', age: 30 }, { name: 'name', age: 40 }]

You can make more complicated fixture factory with custom attributes of generator.

1import { FixtureFactory } from '@reflow-work/test-fixture-factory';
2
3const integerFactory = new FixtureFactory<
4  number,
5  { min: number | undefined; max: number | undefined }
6>((attrs) => {
7  const minNumber = attrs?.min ?? 0;
8  const maxNumber = attrs?.max ?? Number.MAX_SAFE_INTEGER;
9
10  return Math.floor(Math.random() * (maxNumber - minNumber)) + minNumber;
11});
12
13const number = integerFactory.create({ min: 0, max: 10 });

You can also composite those factories.

1import { FixtureFactory } from '@reflow-work/test-fixture-factory';
2
3type UserType = {
4  name: string;
5  age: number;
6};
7
8const integerFactory = new FixtureFactory<
9  number,
10  { min: number | undefined; max: number | undefined }
11>((attrs) => {
12  const minNumber = attrs?.min ?? 0;
13  const maxNumber = attrs?.max ?? Number.MAX_SAFE_INTEGER;
14
15  return Math.floor(Math.random() * (maxNumber - minNumber)) + minNumber;
16});
17
18const userFactory = new FixtureFactory<UserType>(() => {
19  return {
20    name: 'name',
21    age: integerFactory.create({ min: 0, max: 100 }),
22  };
23});

When creating a FixtureFactory using a class, you should use | undefined = undefined to the fields instead of ?(optional). This is because the generator is set to return Required<T>. This prevents merging non-existent keys when overriding attrs.

See also When to use typescript optional property? How is it different from declaring property as undefined

1class UserClass {
2  constructor(
3    public name: string,
4    public age: number | undefined = undefined // instead of `number?`
5  );
6}
7
8const userFactory = new FixtureFactory<UserClass>(() => ...)

For more information, see also test codes

Contributing

To install dependencies:

1bun install

To run test:

1bun test src

This project was created using bun init in bun v1.0.6. Bun is a fast all-in-one JavaScript runtime.