styled-components/src/utils/test/interleave.test.js

**This is a work in progress** based off of [this demo](https://github.com/geelen/css-components-demo).

import expect from 'expect'
import interleave from '../interleave'

describe('interleave', () => {
  it('blindly interleave', () => {
    expect(interleave([], [])).toEqual([undefined])
    expect(interleave(['foo'], [])).toEqual(['foo'])
    expect(interleave(['foo'], [1])).toEqual(['foo', 1, undefined])
    expect(interleave(['foo', 'bar'], [1])).toEqual(['foo', 1, 'bar'])
  })
  it('should be driven off the number of interpolations', () => {
    expect(interleave(['foo', 'bar'], [])).toEqual(['foo'])
    expect(interleave(['foo', 'bar', 'baz'], [1])).toEqual(['foo', 1, 'bar'])
    expect(interleave([], [1])).toEqual([undefined, 1, undefined])
    expect(interleave(['foo'], [1, 2, 3])).toEqual(['foo', 1, undefined, 2, undefined, 3, undefined])
  })
})