readiness-manager/src/spec.ts

👨‍💼 Define when your app is ready

import { ERRORS, ActionExecutionError } from './error';
import { ReadinessManager } from './index';

/**
 * Waits a given milliseconds before resolving.
 * @param time - The time to wait
 */
const wait = (time = 0): Promise<unknown> => new Promise((resolve) => setTimeout(resolve, time));

describe('lib/readinessManager', () => {
    let readyManager: ReadinessManager;

    beforeEach(() => {
        jest.isolateModules(() => {
            readyManager = require('./index').default;
        });
    });

    afterEach(jest.clearAllMocks);

    describe('API', () => {
        it.each(['register', 'run', 'onReady', 'onActionReady', 'status', 'onError'])(
            'Exposes public API (%p)',
            (property) => {
                expect(typeof (readyManager as any)[property]).toBe('function');
            }
        );

        it.each(['beacons', 'callbacks', 'execute', 'updateBeacon'])(
            'Encapsulates private properties (%p)',
            (property) => {
                expect((readyManager as any)[property]).toBeUndefined();
            }
        );
    });

    describe('status', () => {
        describe('When no actions are registered', () => {
            it('Return an empty object', () => {
                expect(readyManager.status()).toEqual({});
            });
        });

        describe('When some actions exists', () => {
            it('Group registered actions with same status', async () => {
                readyManager.register('success', () => Promise.resolve());
                readyManager.register('other', () => Promise.resolve());
                readyManager.register('fail', () => Promise.reject(new Error()));

                readyManager.run();
                await wait(10);

                const status = readyManager.status();

                expect(status.resolved).toEqual(['success', 'other']);
                expect(status.rejected).toEqual(['fail']);
            });
        });
    });

    describe('register', () => {
        describe('When given action name is unique', () => {
            it('Registers action and name as beacon with not_started status', () => {
                readyManager.register('action', () => true);

                expect(readyManager.status().not_started).toHaveLength(1);
            });
        });

        describe('When action name was already registered', () => {
            it('Throws upon registration', () => {
                readyManager.register('once', () => true);

                expect(() => readyManager.register('once', () => true)).toThrowError(ERRORS.BEACON_ALREADY_EXISTS);
            });
        });
    });

    describe('run', () => {
        beforeEach(() => {
            readyManager.register('action1', wait);
            readyManager.register('action2', wait);
        });

        it('Executes all given actions', async () => {
            expect(readyManager.status().not_started).toHaveLength(2);

            readyManager.run();

            expect(readyManager.status().not_started).toBeUndefined();

            expect(readyManager.status().pending).toHaveLength(2);
        });
    });

    describe('ready', () => {
        it('Returns false by default', () => {
            expect(readyManager.ready).toBeFalsy();
        });

        describe('When all actions resolves', () => {
            beforeEach(() => {
                readyManager.register('action1', () => true);
                readyManager.register('action2', () => true);

                readyManager.run();
            });

            it('Is ready', () => expect(readyManager.ready).toBeTruthy());
        });

        describe('When some action fails', () => {
            beforeEach(() => {
                readyManager.register('action1', () => true);
                readyManager.register('action2', () => {
                    throw new Error('What?');
                });

                readyManager.run();
            });

            it('Is not ready', () => expect(readyManager.ready).toBeFalsy());
        });
    });

    describe('onReady', () => {
        let callback: jest.Mock;

        beforeEach(() => (callback = jest.fn()));

        const ensureFresh = () => {
            readyManager.register('action1', () => true);
            expect(callback).toHaveBeenCalledTimes(0);
        };

        describe('When process is not ready', () => {
            it('Registers given callback', () => {
                const callback = jest.fn();
                ensureFresh();

                readyManager.onReady(callback);
                readyManager.run();

                expect(callback).toHaveBeenCalledTimes(1);
            });
        });

        describe('When process is already ready', () => {
            it('Activates immediately given callback', () => {
                ensureFresh();

                readyManager.run();
                readyManager.onReady(callback);

                expect(callback).toHaveBeenCalledTimes(1);
            });
        });
    });

    describe('onActionReady', () => {
        let callback: jest.Mock;

        beforeEach(() => (callback = jest.fn()));

        it('Throws when action does not exists', () => {
            expect(() => readyManager.onActionReady('Hey', () => false)).toThrowError(ERRORS.BEACON_DOES_NOT_EXISTS);
        });

        describe('When action is not ready', () => {
            it('Triggers callback once desired aciton is ready', async () => {
                readyManager.register('some', () => true);
                readyManager.register('thing', () => wait(500));
                readyManager.register('other', () => wait(1000));

                readyManager.onActionReady('thing', callback);

                readyManager.run();
                expect(callback).toHaveBeenCalledTimes(0);

                await wait(500);

                expect(callback).toHaveBeenCalledTimes(1);
            });
        });

        describe('When action is already resolved', () => {
            it('Triggers immediately given callback', () => {
                readyManager.register('some', () => true);

                readyManager.run();
                readyManager.onActionReady('some', callback);

                expect(callback).toHaveBeenCalledTimes(1);
            });
        });
    });

    describe('onError', () => {
        let logger: jest.Mock;
        beforeEach(() => (logger = jest.fn()));

        describe('When no errors occur', () => {
            beforeEach(() => {
                readyManager.register('success', () => true);
                readyManager.onError((error) => {
                    logger(error);
                });
                readyManager.run();
            });

            it("Won't trigger error handler", () => {
                expect(logger).toHaveBeenCalledTimes(0);
            });
        });

        describe('When error occur', () => {
            const error = new Error('Oh man, that did not worked!');

            beforeEach(() => {
                readyManager.register('success', () => {
                    throw error;
                });

                readyManager.onError((error) => {
                    logger(error);
                });

                readyManager.run();
            });

            it('Triggers consumer handler with beacon execution error', () => {
                expect(logger).toHaveBeenCalledWith(new ActionExecutionError('success', 1, error));
            });
        });
    });

    describe('Chainable', () => {
        it('Expose public chainable api', () => {
            const ready = jest.fn();
            const error = jest.fn();

            readyManager.register('action', () => true);

            readyManager.run().onReady(ready).onError(error);

            expect(ready).toHaveBeenCalledTimes(1);
            expect(error).toHaveBeenCalledTimes(0);
        });
    });
});