Add jest matcher

[a-xin]

Adding jest matchers to conveniently use targaryen with jest.

See #129

Usage:

const { getDatabase, toAllowRead, toAllowUpdate, toAllowWrite, json } = require('targaryen/plugins/jest');

expect.extend({
  toAllowRead,
  toAllowUpdate,
  toAllowWrite,
});

const RULES_PATH = 'database.rules.json';
const rules = json.loadSync(RULES_PATH);
const initialData = {};

const database = getDatabase(rules, initialData);

test('basic', () => {
  expect(database.as(null)).not.toAllowRead('/user');
  expect(database.as(null)).toAllowRead('/public');
  expect(database.as({ uid: '1234'})).toAllowWrite('/user/1234', {
    name: 'Anna',
  });
});

or using the generic matcher:

const { getDebugDatabase, toBeAllowed, json } = require('targaryen/plugins/jest');

expect.extend({
  toBeAllowed,
});

const RULES_PATH = 'database.rules.json';
const rules = json.loadSync(RULES_PATH);
const initialData = {};

// NOTE: Create a database with debug set to true for detailed errors
const database = getDebugDatabase(rules, initialData);

test('generic', () => {
  expect(database.as(null).read('/user')).not.toBeAllowed();
  expect(database.as({ uid: '1234' }).write('/user/1234', {
    name: 'Anna',
  })).toBeAllowed();
});

[a-xin]

@dinoboff What do you think of the approach and the interfaces? Happy to add tests and docs if the code looks fine

[coveralls]

Coverage remained the same at 95.404% when pulling 4f3fc3b on a-xin:add-jest-matcher into f3281a0 on goldibex:master.

[coveralls]

Coverage remained the same at 95.404% when pulling 396bd0d on a-xin:add-jest-matcher into f3281a0 on goldibex:master.

[dinoboff]

Thanks, I like the interface. I will include once there are integration test and documentation similar to the Jasmine plugin.

Note that targaryen still support node 4.

[dinoboff]

Also, in v4, I might move the plugins to their own packages. Core and plugins will still be hosted together in that repo.

[a-xin]

Good shout about node 4! With jest supporting only 6+ out of the box, it would make sense to put the plugin into a separate package right away and have it require node 6+.
Otherwise, as it's not the plugin itself but only its tests that will require node 6+ I could add them to this PR and make the jest tests only run when on a supported node version (as a temporary hack until the plugins get extracted)

[dinoboff]

Looking good.

Thanks!

[dinoboff]

Could you please change the version test. Either use grep or change the previous test to use cut. cut is probably better.

[dinoboff]

Thanks @a-xin. Published with 3.1.0.