require("../env");

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

var assert = require("assert");

module.exports = {

  topic: function() {

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

  },

  "calls the function once": function(transition) {

    var count = 0;

    transition.call(function() { ++count; });

    assert.equal(count, 1);

  },

  "passes any optional arguments": function(transition) {

    var abc;

    transition.call(function(selection, a, b, c) { abc = [a, b, c]; }, "a", "b", "c");

    assert.deepEqual(abc, ["a", "b", "c"]);

  },

  "passes the transition as the first argument": function(transition) {

    var t;

    transition.call(function(x) { t = x; });

    assert.isTrue(t === transition);

  },

  "uses the transition as the context": function(transition) {

    var t;

    transition.call(function() { t = this; });

    assert.isTrue(t === transition);

  },

  "returns the current transition": function(transition) {

    assert.isTrue(transition.call(function() {}) === transition);

  }

};