const _ = require('lodash');
let suite;

beforeEach(() => {
    suite = {
        sampleData: [1, 2, 3],
        sampleFunc: jest.fn(value => value),
        sampleDataLength: 3
    };
});

afterEach(() => {
    suite.sampleFunc.mockClear();
    suite = null;
});

describe('lodash wrapper', () => {
    it('toArray', () => {
        const chain = _(suite.sampleData)
            .map(value => suite.sampleFunc(value))
            .toArray();

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength); // 0 times

        console.log(chain.size());
        const first = _.first(chain);

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength); // 3 times
    });

    it('value', () => {
        const chain = _(suite.sampleData)
            .map(value => suite.sampleFunc(value))
            .value();

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength);

        console.log(chain.length);
        const first = _.first(chain);

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength);
    });
});

describe('chain', () => {
    it('toArray', () => {
        const chain = _.chain(suite.sampleData)
            .map(value => suite.sampleFunc(value))
            .toArray();

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleData.length); // 0 times

        console.log(chain.size());
        const first = _.first(chain);

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleData.length); // called 6 times instead of 3
    });

    it('value', () => {
        const chain = _.chain(suite.sampleData)
            .map(value => suite.sampleFunc(value))
            .value();

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength);

        console.log(chain.length);
        const first = _.first(chain);

        expect(suite.sampleFunc).toHaveBeenCalledTimes(suite.sampleDataLength);
    });
});