Unit tests for a function that calculates items that fit in a row, given row width, item width, and gutter between items.

module.js

module.exports = {
  /**
   * Given the width of a container, the width of an item, and the gutter between inner items,
   * calculate the number of items that can fit on a single row inside the container.
   * @param  {number} rowWidth    the width, in pixels, of the container
   * @param  {number} itemWidth   the width of each individual item in the container
   * @param  {number} [gutter]    the space, in pixels, between each item (optional)
   * @return {number}             the number of items that fit in a row without overflow, never less than 1
   */
  calculateItemsPerRow: function (rowWidth, itemWidth, gutter) {
    var itemsPerRow;
    // magic
    return itemsPerRow;
  }
}

test.js

var should = require('should'); // from should.js, but optionally chai.should
var calculateItemsPerRow = require('./module').calculateItemsPerRow;

describe("calculateItemsPerRow", function () {
  it("should return the number of items that can fit in a row", function () {
    calculateItemsPerRow(900, 300).should.equal(3);
    calculateItemsPerRow(1000, 300, 50).should.equal(3);
    calculateItemsPerRow(1000, 300, 51).should.equal(2);
    calculateItemsPerRow(1000, 50).should.equal(20);
    calculateItemsPerRow(1000, 50, 200).should.equal(4);
  });

  it("should never return less than one", function () {
    calculateItemsPerRow(200, 300).should.equal(1);
    calculateItemsPerRow(200, 200, 10).should.equal(1);
    calculateItemsPerRow(100, 1, 200).should.equal(1);
  });
});