d3_scale_test.js

/* Implementation */

function getXScale(dimensions, data) {
  var range = [0, dimensions.width];
  var domain = [0, data.length - 1];
  return d3.scale.linear().domain(domain).range(range);
}

/* Test */

describe('#getXScale', function() {
  it('returns the correct domain and range', function() {
    var  data = [0, 5, 10, 30, 50];
    var dimensions = {
      width: 100,
      height: 300
    };
    
    var scale = getXScale(dimensions, data);
    assert.deepEqual(scale.range(), [0, 100]);
    assert.deepEqual(scale.domain(), [0, 4]);
  });
});