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mock-build

npm package Node.js version GitHub Release GitHub Test

Create reusable mocks using the builder pattern in Typescript

Installation

yarn add mock-build

Usage

Basic usage

interface UserInfo {
  id: number;
  userName: string;
  email: string;
}

const userInfo = mockBuilder<UserInfo>()
  .id(1)
  .userName('foo')
  .email('[email protected]')
  .build();

A note of caution: when building objects from scratch, the builder currently cannot ensure that all mandatory fields have been set. The built object might thus violate the contract of the given interface. For example, the following will compile (see also the example in the tests):

const brokenUserInfo = mockBuilder<UserInfo>().build();

A way around this is to use template objects (see Usage with template objects).

Another way is to use strictMockBuilder (see Usage with strictMockBuilder).

Reusing builder instances

const baseUserInfo = mockBuilder<UserInfo>()
  .id(1)
  .userName('foo')
  .email('[email protected]');

const userInfo = baseUserInfo.id(2).build();
// {
//   id: 2,
//   userName: "foo",
//   email: "[email protected]"
// }

const otherUserInfo = baseUserInfo.id(3).build();
// {
//   id: 3,
//   userName: "foo",
//   email: "[email protected]"
// }

Usage with template objects

You can also specify a template object, which allows easy creation of variation of objects. This is especially useful for making test data setup more readable:

const defaultUserInfo: UserInfo = {
  id: 1,
  userName: 'foo',
  email: '[email protected]',
};

const modifiedUserInfo = mockBuilder(defaultUserInfo).id(2).build();

Notes:

  • With this approach, if the template object conforms to the interface, the built object will, too.
  • The builder will effectively create and modify a shallow copy of the template object.

Usage with class object

You can also specify a class object.

class UserInfo {
  id!: number;
  userName!: string;
  email!: string;
}

const userInfo = mockBuilder(UserInfo) // note that ( ) is used instead of < > here
  .id(1)
  .userName('foo')
  .email('[email protected]')
  .build();

Moreover, you can also specify a class object with a template object.

class UserInfo {
  id!: number;
  userName!: string;
  email!: string;
}

const userInfo = mockBuilder(UserInfo, {id: 1, userName: 'foo'})
                   .userName:('foo bar')
                   .email('[email protected]')
                   .build();

Usage with strictMockBuilder

strictMockBuilder is used to make sure all variables are initialized.

interface UserInfo {
  id: number;
  userName: string;
  email: string;
}

const userInfo = strictMockBuilder<UserInfo>().id(1).build(); // This expression is not callable.
// Type 'never' has no call signatures.ts(2349)

All variables must be initialized before calling build().

const userInfo = strictMockBuilder<UserInfo>()
  .id(1)
  .userName('foo')
  .email('[email protected]')
  .build(); // build() is called successfully

Notes: strictMockBuilder does not support classes.

Contributing

  1. Fork it!
  2. Create your feature branch: git checkout -b my-new-feature
  3. Commit your changes: git commit -am 'Add some feature'
  4. Push to the branch: git push origin my-new-feature
  5. Submit a pull request :D

Credits

https://github.com/Vincent-Pang/builder-pattern is the original repository that this was forked from.

License

This project is licensed under the MIT License - see the LICENSE file for details