require("../env");

require("../../d3");

var assert = require("assert");

module.exports = {

  topic: function() {

    return d3.select("body").append("div").transition();

  },

  "is approximately equal to now": function(transition) {

    var time = transition.time;

    assert.inDelta(time, Date.now(), 20);

  },

  "increases monotonically across transitions": function(transition) {

    var now = Date.now, then = Date.now();

    try {

      Date.now = function() { return ++then; };

      var t0 = d3.select("body").append("div").transition(),

          t1 = d3.select("body").append("div").transition();

      assert.isTrue(t1.time > t0.time);

    } finally {

      Date.now = now;

    }

  },

  "is inherited by subtransitions": function(transition) {

    var now = Date.now, then = Date.now();

    try {

      Date.now = function() { return ++then; };

      var t0 = d3.select("body").append("div").transition(),

          t1 = t0.transition();

      assert.equal(t1.time, t0.time);

    } finally {

      Date.now = now;

    }

  }

};