55 lines
1.3 KiB
JavaScript
55 lines
1.3 KiB
JavaScript
/* eslint-env jest */
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const { compose } = require('./')
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const add2 = x => x + 2
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const mul3 = x => x * 3
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describe('compose()', () => {
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it('throws when no functions is passed', () => {
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expect(() => compose()).toThrow(TypeError)
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expect(() => compose([])).toThrow(TypeError)
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})
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it('applies from left to right', () => {
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expect(compose(add2, mul3)(5)).toBe(21)
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})
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it('accepts functions in an array', () => {
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expect(compose([add2, mul3])(5)).toBe(21)
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})
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it('can apply from right to left', () => {
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expect(compose({ right: true }, add2, mul3)(5)).toBe(17)
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})
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it('accepts options with functions in an array', () => {
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expect(compose({ right: true }, [add2, mul3])(5)).toBe(17)
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})
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it('can compose async functions', async () => {
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expect(
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await compose(
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{ async: true },
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async x => x + 2,
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async x => x * 3
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)(5)
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).toBe(21)
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})
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it('first function receives this and all args', () => {
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expect.assertions(2)
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const expectedArgs = [Math.random(), Math.random()]
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const expectedThis = {}
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compose(
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function (...args) {
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expect(this).toBe(expectedThis)
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expect(args).toEqual(expectedArgs)
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},
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// add a second function to use the one function special case
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Function.prototype
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).apply(expectedThis, expectedArgs)
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})
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})
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