jest-structure

jest-structure

Custom Jest matchers to test Structure instances.

Example usage

expect(user).toBeValidStructure();

expect(user).toBeInvalidStructure();

expect(user).toHaveInvalidAttribute(['name']);

expect(user).toHaveInvalidAttribute(['name'], ['"name" is required']);

expect(user).toHaveInvalidAttribute(['name'], expect.arrayContaining(['"name" is required']));

expect(user).toHaveInvalidAttributes([
  { path: ['name'], messages: expect.arrayContaining(['"name" is required']) },
  {
    path: ['age'],
    messages: ['"age" must be larger than or equal to 2', '"age" must be a positive number'],
  },
]);

Installation

jest-structure is available in npm, so you can install it with npm or yarn as a development dependency:

npm install --save-dev jest-structure

# or

yarn --dev add jest-structure

Setup

After installing, you need to tell Jest to use jest-structure, this can be done in two ways:

1. By importing and manually adding it to Jest (in a setup file or directly in the top of your test file):

import jestStructure from 'jest-structure';

expect.extend(jestStructure);

1. By allowing jest-structure to add itself to Jest matchers:

import 'jest-structure/extend-expect';

Matchers

toBeValidStructure()

This matcher passes if the structure is valid:

const User = attributes({
  name: { type: String, required: true },
})(class User {});

const validUser = new User({ name: 'Me' });

expect(validUser).toBeValidStructure(); // passes

const invalidUser = new User();

expect(invalidUser).toBeValidStructure(); // fails

toBeInvalidStructure()

This matcher passes if the structure is invalid:

const User = attributes({
  name: { type: String, required: true },
})(class User {});

const invalidUser = new User();

expect(invalidUser).toBeInvalidStructure(); // passes

const validUser = new User({ name: 'Me' });

expect(validUser).toBeInvalidStructure(); // fails

toHaveInvalidAttribute(path, messages)

This matcher allows you to assert that a single attribute of the structure is invalid, optionally passing the array of error messages for that attribute:

const User = attributes({
  name: { type: String, required: true },
  age: { type: Number, required: true },
})(class User {});

const user = new User({ age: 42 });

// passes, because name is invalid
expect(user).toHaveInvalidAttribute(['name']);

// fails, because age is valid
expect(user).toHaveInvalidAttribute(['age']);

// passes, because name is invalid with this message
expect(user).toHaveInvalidAttribute(['name'], ['"name" is required']);

// fails, because name is invalid but not with this message
expect(user).toHaveInvalidAttribute(['name'], ['"name" is not cool']);

// passes. Notice that you can even use arrayContaining to check for a subset of the errros
expect(user).toHaveInvalidAttribute(['name'], expect.arrayContaining(['"name" is required']));

// passes. And stringContaining can be used as well
expect(user).toHaveInvalidAttribute(['name'], [expect.stringContaining('required')]);

toHaveInvalidAttributes([ { path, messages } ])

This matcher allows you to assert that multiple attributes of the structure are invalid, optionally passing the array of error messages for each attribute:

const User = attributes({
  name: { type: String, required: true },
  age: { type: Number, required: true },
})(class User {});

const user = new User({ age: 42 });

// passes, because name is invalid
expect(user).toHaveInvalidAttributes([{ path: ['name'] }]);

// fails, because age is valid
expect(user).toHaveInvalidAttributes([{ path: ['age'] }]);

// fails, because name is invalid but age is valid
expect(user).toHaveInvalidAttributes([{ path: ['name'] }, { path: ['age'] }]);

// passes, because name is invalid with this message
expect(user).toHaveInvalidAttributes([{ path: ['name'], messages: ['"name" is required'] }]);

// fails, because name is invalid but not with this message
expect(user).toHaveInvalidAttributes([{ path: ['name'], messages: ['"name" is not cool'] }]);

// passes. Notice that you can even use arrayContaining to check for a subset of the errros
expect(user).toHaveInvalidAttributes([
  { path: ['name'], messages: expect.arrayContaining(['"name" is required']) },
]);

// passes. And stringContaining can be used as well
expect(user).toHaveInvalidAttributes([
  { path: ['name'], messages: [expect.stringContaining('required')] },
]);