ts-prime/src/pipe.test.ts

A utility library for JavaScript and Typescript.

import { pipe } from './pipe';
import { map } from './map';
import { take } from './take';
import { filter } from './filter';
import { identity } from './identity';

it('should pipe a single operation', () => {
  const result = pipe(1, x => x * 2);
  expect(result).toEqual(2);
});

it('should pipe operations', () => {
  const result = pipe(
    1,
    x => x * 2,
    x => x * 3
  );
  expect(result).toEqual(6);
});

describe('lazy', () => {
  it('lazy map + take', () => {
    const count = jest.fn();
    const result = pipe(
      [1, 2, 3],
      map(x => {
        count();
        return x * 10;
      }),
      take(2)
    );
    expect(count).toHaveBeenCalledTimes(2);
    expect(result).toEqual([10, 20]);
  });

  it('lazy map + filter + take', () => {
    const count = jest.fn();
    const result = pipe(
      [1, 2, 3, 4, 5],
      map(x => {
        count();
        return x * 10;
      }),
      filter(x => (x / 10) % 2 === 1),
      take(2)
    );
    expect(count).toHaveBeenCalledTimes(3);
    expect(result).toEqual([10, 30]);
  });

  it('break lazy', () => {
    const count = jest.fn();
    const result = pipe(
      [1, 2, 3],
      map(x => {
        count();
        return x * 10;
      }),
      x => x,
      take(2)
    );
    expect(count).toHaveBeenCalledTimes(3);
    expect(result).toEqual([10, 20]);
  });

  it('multiple take', () => {
    const count = jest.fn();
    const result = pipe(
      [1, 2, 3],
      map(x => {
        count();
        return x * 10;
      }),
      take(2),
      take(1)
    );
    expect(count).toHaveBeenCalledTimes(1);
    expect(result).toEqual([10]);
  });

  it('multiple lazy', () => {
    const count = jest.fn();
    const count2 = jest.fn();
    const result = pipe(
      [1, 2, 3, 4, 5, 6, 7],
      map(x => {
        count();
        return x * 10;
      }),
      take(4),
      identity,
      map(x => {
        count2();
        return x * 10;
      }),
      take(2)
    );
    expect(count).toHaveBeenCalledTimes(4);
    expect(count2).toHaveBeenCalledTimes(2);
    expect(result).toEqual([100, 200]);
  });
});