text: require( 'babel/register' );
  
  var vows = require("vows"),
      load = require("../load"),
      assert = require("../assert");
  
  var suite = vows.describe("d3.ease");
  
  suite.addBatch({
    "ease": {
      topic: load("interpolate/ease").expression("d3.ease"),
      "supports linear easing": function(ease) {
        var e = ease("linear");
        assert.inDelta(e(.5), .5, 1e-6);
      },
      "supports polynomial easing": function(ease) {
        var e = ease("poly", 2);
        assert.inDelta(e(.5), .25, 1e-6);
      },
      "supports quadratic easing": function(ease) {
        var e = ease("quad");
        assert.inDelta(e(.5), .25, 1e-6);
      },
      "supports cubic easing": function(ease) {
        var e = ease("cubic");
        assert.inDelta(e(.5), .125, 1e-6);
      },
      "supports sinusoidal easing": function(ease) {
        var e = ease("sin");
        assert.inDelta(e(.5), 1 - Math.cos(Math.PI / 4), 1e-6);
      },
      "supports exponential easing": function(ease) {
        var e = ease("exp");
        assert.inDelta(e(.5), 0.03125, 1e-6);
      },
      "supports circular easing": function(ease) {
        var e = ease("circle");
        assert.inDelta(e(.5), 0.133975, 1e-6);
      },
      "supports elastic easing": function(ease) {
        var e = ease("elastic");
        assert.inDelta(e(.5), 0.976061, 1e-6);
      },
      "supports back easing": function(ease) {
        var e = ease("back");
        assert.inDelta(e(.5), -0.0876975, 1e-6);
      },
      "supports bounce easing": function(ease) {
        var e = ease("bounce");
        assert.inDelta(e(.5), 0.765625, 1e-6);
      },
      "invalid eases and modes default to linear-in": function(ease) {
        var e = ease("__proto__-__proto__");
        assert.strictEqual(e(0), 0);
        assert.strictEqual(e(.5), .5);
        assert.strictEqual(e(1), 1);
        var e = ease("hasOwnProperty-constructor");
        assert.strictEqual(e(0), 0);
        assert.strictEqual(e(.5), .5);
        assert.strictEqual(e(1), 1);
      },
      "all easing functions return exactly 0 for t = 0": function(ease) {
        assert.strictEqual(ease("linear")(0), 0);
        assert.strictEqual(ease("poly", 2)(0), 0);
        assert.strictEqual(ease("quad")(0), 0);
        assert.strictEqual(ease("cubic")(0), 0);
        assert.strictEqual(ease("sin")(0), 0);
        assert.strictEqual(ease("exp")(0), 0);
        assert.strictEqual(ease("circle")(0), 0);
        assert.strictEqual(ease("elastic")(0), 0);
        assert.strictEqual(ease("back")(0), 0);
        assert.strictEqual(ease("bounce")(0), 0);
      },
      "all easing functions return exactly 1 for t = 1": function(ease) {
        assert.strictEqual(ease("linear")(1), 1);
        assert.strictEqual(ease("poly", 2)(1), 1);
        assert.strictEqual(ease("quad")(1), 1);
        assert.strictEqual(ease("cubic")(1), 1);
        assert.strictEqual(ease("sin")(1), 1);
        assert.strictEqual(ease("exp")(1), 1);
        assert.strictEqual(ease("circle")(1), 1);
        assert.strictEqual(ease("elastic")(1), 1);
        assert.strictEqual(ease("back")(1), 1);
        assert.strictEqual(ease("bounce")(1), 1);
      },
      "the -in suffix returns the identity": function(ease) {
        assert.inDelta(ease("linear-in")(.25), ease("linear")(.25), 1e-6);
        assert.inDelta(ease("quad-in")(.75), ease("quad")(.75), 1e-6);
      },
      "the -out suffix returns the reverse": function(ease) {
        assert.inDelta(ease("sin-out")(.25), 1 - ease("sin-in")(.75), 1e-6);
        assert.inDelta(ease("bounce-out")(.25), 1 - ease("bounce-in")(.75), 1e-6);
        assert.inDelta(ease("elastic-out")(.25), 1 - ease("elastic-in")(.75), 1e-6);
      },
      "the -in-out suffix returns the reflection": function(ease) {
        assert.inDelta(ease("sin-in-out")(.25), .5 * ease("sin-in")(.5), 1e-6);
        assert.inDelta(ease("bounce-in-out")(.25), .5 * ease("bounce-in")(.5), 1e-6);
        assert.inDelta(ease("elastic-in-out")(.25), .5 * ease("elastic-in")(.5), 1e-6);
      },
      "the -out-in suffix returns the reverse reflection": function(ease) {
        assert.inDelta(ease("sin-out-in")(.25), .5 * ease("sin-out")(.5), 1e-6);
        assert.inDelta(ease("bounce-out-in")(.25), .5 * ease("bounce-out")(.5), 1e-6);
        assert.inDelta(ease("elastic-out-in")(.25), .5 * ease("elastic-out")(.5), 1e-6);
      },
      "clamps input time": function(ease) {
        var e = ease("linear");
        assert.inDelta(e(-1), 0, 1e-6);
        assert.inDelta(e(2), 1, 1e-6);
      },
      "poly": {
        "supports an optional polynomial": function(ease) {
          var e = ease("poly", 1);
          assert.inDelta(e(.5), .5, 1e-6);
          var e = ease("poly", .5);
          assert.inDelta(e(.5), Math.SQRT1_2, 1e-6);
        }
      },
      "elastic": {
        "supports an optional amplifier (>1)": function(ease) {
          var e = ease("elastic", 1.5);
          assert.inDelta(e(.5), 0.998519, 1e-6);
        },
        "supports an optional amplifier (>1) and period (>0)": function(ease) {
          var e = ease("elastic", 1.5, .5);
          assert.inDelta(e(.5), 0.96875, 1e-6);
        }
      },
      "back": {
        "supports an optional speed": function(ease) {
          var e = ease("back", 2);
          assert.inDelta(e(.5), -0.125, 1e-6);
        }
      }
    }
  });
  
  suite.export(module);
  