spy-test.js

"use strict";

var referee = require("referee");
var createSpy = require("../lib/sinon/spy");
var sinonMatch = require("../lib/sinon/match");
var assert = referee.assert;
var refute = referee.refute;

function spyCalledTests(method) {
    return function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("returns false if spy was not called", function () {
            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns true if spy was called with args", function () {
            this.spy(1, 2, 3);

            assert(this.spy[method](1, 2, 3));
        });

        it("returns true if called with args at least once", function () {
            this.spy(1, 3, 3);
            this.spy(1, 2, 3);
            this.spy(3, 2, 3);

            assert(this.spy[method](1, 2, 3));
        });

        it("returns false if not called with args", function () {
            this.spy(1, 3, 3);
            this.spy(2);
            this.spy();

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns false if not called with undefined", function () {
            this.spy();

            assert.isFalse(this.spy[method](undefined));
        });

        it("returns true for partial match", function () {
            this.spy(1, 3, 3);
            this.spy(2);
            this.spy();

            assert(this.spy[method](1, 3));
        });

        it("matchs all arguments individually, not as array", function () {
            this.spy([1, 2, 3]);

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("uses matcher", function () {
            this.spy("abc");

            assert(this.spy[method](sinonMatch.typeOf("string")));
        });

        it("uses matcher in object", function () {
            this.spy({ some: "abc" });

            assert(this.spy[method]({ some: sinonMatch.typeOf("string") }));
        });

        // https://github.com/sinonjs/sinon/issues/1245
        // Using the `calledWithMatch` should work with objects that don't have
        // a hasOwnProperty function.
        describe("when called with an Object without a prototype", function () {
            it("must not throw", function () {
                var spy = this.spy;
                var objectWithoutPrototype = Object.create(null);

                objectWithoutPrototype.something = 2;

                spy[method]({
                    foo: 1,
                    objectWithoutPrototype: objectWithoutPrototype
                });

                refute.exception(function () {
                    spy.calledWithMatch({
                        objectWithoutPrototype: objectWithoutPrototype
                    });
                });
            });
        });
    };
}

function spyAlwaysCalledTests(method) {
    return function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("returns false if spy was not called", function () {
            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns true if spy was called with args", function () {
            this.spy(1, 2, 3);

            assert(this.spy[method](1, 2, 3));
        });

        it("returns false if called with args only once", function () {
            this.spy(1, 3, 3);
            this.spy(1, 2, 3);
            this.spy(3, 2, 3);

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns false if not called with args", function () {
            this.spy(1, 3, 3);
            this.spy(2);
            this.spy();

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns true for partial match", function () {
            this.spy(1, 3, 3);

            assert(this.spy[method](1, 3));
        });

        it("returns true for partial match on many calls", function () {
            this.spy(1, 3, 3);
            this.spy(1, 3);
            this.spy(1, 3, 4, 5);
            this.spy(1, 3, 1);

            assert(this.spy[method](1, 3));
        });

        it("matchs all arguments individually, not as array", function () {
            this.spy([1, 2, 3]);

            assert.isFalse(this.spy[method](1, 2, 3));
        });
    };
}

function spyNeverCalledTests(method) {
    return function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("returns true if spy was not called", function () {
            assert(this.spy[method](1, 2, 3));
        });

        it("returns false if spy was called with args", function () {
            this.spy(1, 2, 3);

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns false if called with args at least once", function () {
            this.spy(1, 3, 3);
            this.spy(1, 2, 3);
            this.spy(3, 2, 3);

            assert.isFalse(this.spy[method](1, 2, 3));
        });

        it("returns true if not called with args", function () {
            this.spy(1, 3, 3);
            this.spy(2);
            this.spy();

            assert(this.spy[method](1, 2, 3));
        });

        it("returns false for partial match", function () {
            this.spy(1, 3, 3);
            this.spy(2);
            this.spy();

            assert.isFalse(this.spy[method](1, 3));
        });

        it("matchs all arguments individually, not as array", function () {
            this.spy([1, 2, 3]);

            assert(this.spy[method](1, 2, 3));
        });
    };
}

describe("spy", function () {
    it("does not throw if called without function", function () {
        refute.exception(function () {
            createSpy.create();
        });
    });

    it("does not throw when calling anonymous spy", function () {
        var spy = createSpy.create();

        refute.exception(function () {
            spy();
        });

        assert(spy.called);
    });

    it("returns spy function", function () {
        var func = function () {};
        var spy = createSpy.create(func);

        assert.isFunction(spy);
        refute.same(func, spy);
    });

    it("mirrors custom properties on function", function () {
        var func = function () {};
        func.myProp = 42;
        var spy = createSpy.create(func);

        assert.equals(spy.myProp, func.myProp);
    });

    it("does not define create method", function () {
        var spy = createSpy.create();

        refute.defined(spy.create);
    });

    it("does not overwrite original create property", function () {
        var func = function () {};
        var object = func.create = {};
        var spy = createSpy.create(func);

        assert.same(spy.create, object);
    });

    it("sets up logging arrays", function () {
        var spy = createSpy.create();

        assert.isArray(spy.args);
        assert.isArray(spy.returnValues);
        assert.isArray(spy.thisValues);
        assert.isArray(spy.exceptions);
    });

    it("works with getters", function () {
        var object = {
            get property() {
                return 42;
            }
        };
        var spy = createSpy(object, "property", ["get"]);

        assert.equals(object.property, 42);
        assert(spy.get.calledOnce);
    });

    it("works with setters", function () {
        var object = {
            get test() {
                return this.property;
            },
            set test(value) {
                this.property = value * 2;
            }
        };
        var spy = createSpy(object, "test", ["set"]);

        object.test = 42;
        assert(spy.set.calledOnce);
        assert(spy.set.calledWith(42));

        assert.equals(object.test, 84);
        assert.equals(object.property, 84);
    });

    it("works with setters and getters combined", function () {
        var object = {
            get test() {
                return this.property;
            },
            set test(value) {
                this.property = value * 2;
            }
        };
        var spy = createSpy(object, "test", ["get", "set"]);

        object.test = 42;
        assert(spy.set.calledOnce);

        assert.equals(object.test, 84);
        assert(spy.get.calledOnce);
    });

    it("creates a spy for Error", function () {
        var originalError = global.Error;
        try {
            assert(createSpy(global, "Error"));
            global.Error = originalError;
        } catch (e) {
            // so test failure doesn't trickle down
            global.Error = originalError;
            referee.fail("Expected spy to be created");
        }
    });

    it("counts with combination of withArgs arguments and order of calling withArgs", function () {
        var object = {
            f1: function () {},
            f2: function () {}
        };

        // f1: the order of withArgs(1), withArgs(1, 1)
        var spy1 = createSpy(object, "f1");
        assert.equals(spy1.callCount, 0);
        assert.equals(spy1.withArgs(1).callCount, 0);
        assert.equals(spy1.withArgs(1, 1).callCount, 0);

        object.f1();
        object.f1(1);
        object.f1(1, 1);
        object.f1(1, 2);

        assert.equals(spy1.callCount, 4);
        assert.equals(spy1.withArgs(1).callCount, 3);
        assert.equals(spy1.withArgs(1, 1).callCount, 1);
        assert.equals(spy1.withArgs(1, 2).callCount, 1);

        // f2: the order of withArgs(1, 1), withArgs(1)
        var spy2 = createSpy(object, "f2");
        assert.equals(spy2.callCount, 0);
        assert.equals(spy2.withArgs(1, 1).callCount, 0);
        assert.equals(spy2.withArgs(1).callCount, 0);

        object.f2();
        object.f2(1);
        object.f2(1, 1);
        object.f2(1, 2);

        assert.equals(spy2.callCount, 4);
        assert.equals(spy2.withArgs(1).callCount, 3);
        assert.equals(spy2.withArgs(1, 1).callCount, 1);
        assert.equals(spy2.withArgs(1, 2).callCount, 1);
    });

    describe(".named", function () {
        it("sets displayName", function () {
            var spy = createSpy();
            var retval = spy.named("beep");
            assert.equals(spy.displayName, "beep");
            assert.same(spy, retval);
        });
    });

    describe("call", function () {
        it("calls underlying function", function () {
            var called = false;

            var spy = createSpy.create(function () {
                called = true;
            });

            spy();

            assert(called);
        });

        it("passs arguments to function", function () {
            var actualArgs;

            var func = function (a, b, c, d) {
                actualArgs = [a, b, c, d];
            };

            var args = [1, {}, [], ""];
            var spy = createSpy.create(func);
            spy(args[0], args[1], args[2], args[3]);

            assert.equals(actualArgs, args);
        });

        it("maintains this binding", function () {
            var actualThis;

            var func = function () {
                actualThis = this;
            };

            var object = {};
            var spy = createSpy.create(func);
            spy.call(object);

            assert.same(actualThis, object);
        });

        it("returns function's return value", function () {
            var object = {};

            var func = function () {
                return object;
            };

            var spy = createSpy.create(func);
            var actualReturn = spy();

            assert.same(actualReturn, object);
        });

        it("throws if function throws", function () {
            var err = new Error();
            var spy = createSpy.create(function () {
                throw err;
            });

            try {
                spy();
                referee.fail("Expected spy to throw exception");
            } catch (e) {
                assert.same(e, err);
            }
        });

        it("retains function length 0", function () {
            var spy = createSpy.create(function () {});

            assert.equals(spy.length, 0);
        });

        it("retains function length 1", function () {
            var spy = createSpy.create(function (a) {}); // eslint-disable-line no-unused-vars

            assert.equals(spy.length, 1);
        });

        it("retains function length 2", function () {
            var spy = createSpy.create(function (a, b) {}); // eslint-disable-line no-unused-vars

            assert.equals(spy.length, 2);
        });

        it("retains function length 3", function () {
            var spy = createSpy.create(function (a, b, c) {}); // eslint-disable-line no-unused-vars

            assert.equals(spy.length, 3);
        });

        it("retains function length 4", function () {
            var spy = createSpy.create(function (a, b, c, d) {}); // eslint-disable-line no-unused-vars

            assert.equals(spy.length, 4);
        });

        it("retains function length 12", function () {
            var func12Args = function (a, b, c, d, e, f, g, h, i, j, k, l) {}; // eslint-disable-line no-unused-vars
            var spy = createSpy.create(func12Args);

            assert.equals(spy.length, 12);
        });
    });

    describe(".called", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false prior to calling the spy", function () {
            assert.isFalse(this.spy.called);
        });

        it("is true after calling the spy once", function () {
            this.spy();

            assert(this.spy.called);
        });

        it("is true after calling the spy twice", function () {
            this.spy();
            this.spy();

            assert(this.spy.called);
        });
    });

    describe(".notCalled", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is true prior to calling the spy", function () {
            assert.isTrue(this.spy.notCalled);
        });

        it("is false after calling the spy once", function () {
            this.spy();

            assert.isFalse(this.spy.notCalled);
        });
    });

    describe(".calledOnce", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false prior to calling the spy", function () {
            assert.isFalse(this.spy.calledOnce);
        });

        it("is true after calling the spy once", function () {
            this.spy();

            assert(this.spy.calledOnce);
        });

        it("is false after calling the spy twice", function () {
            this.spy();
            this.spy();

            assert.isFalse(this.spy.calledOnce);
        });
    });

    describe(".calledTwice", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false prior to calling the spy", function () {
            assert.isFalse(this.spy.calledTwice);
        });

        it("is false after calling the spy once", function () {
            this.spy();

            assert.isFalse(this.spy.calledTwice);
        });

        it("is true after calling the spy twice", function () {
            this.spy();
            this.spy();

            assert(this.spy.calledTwice);
        });

        it("is false after calling the spy thrice", function () {
            this.spy();
            this.spy();
            this.spy();

            assert.isFalse(this.spy.calledTwice);
        });
    });

    describe(".calledThrice", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false prior to calling the spy", function () {
            assert.isFalse(this.spy.calledThrice);
        });

        it("is false after calling the spy twice", function () {
            this.spy();
            this.spy();

            assert.isFalse(this.spy.calledThrice);
        });

        it("is true after calling the spy thrice", function () {
            this.spy();
            this.spy();
            this.spy();

            assert(this.spy.calledThrice);
        });

        it("is false after calling the spy four times", function () {
            this.spy();
            this.spy();
            this.spy();
            this.spy();

            assert.isFalse(this.spy.calledThrice);
        });
    });

    describe(".callCount", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("reports 0 calls", function () {
            assert.equals(this.spy.callCount, 0);
        });

        it("records one call", function () {
            this.spy();

            assert.equals(this.spy.callCount, 1);
        });

        it("records two calls", function () {
            this.spy();
            this.spy();

            assert.equals(this.spy.callCount, 2);
        });

        it("increases call count for each call", function () {
            this.spy();
            this.spy();
            assert.equals(this.spy.callCount, 2);

            this.spy();
            assert.equals(this.spy.callCount, 3);
        });
    });

    describe(".calledOn", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false if spy wasn't called", function () {
            assert.isFalse(this.spy.calledOn({}));
        });

        it("is true if called with thisValue", function () {
            var object = {};
            this.spy.call(object);

            assert(this.spy.calledOn(object));
        });

        if (typeof window !== "undefined") {
            describe("in browser", function () {
                it("is true if called on object at least once", function () {
                    var object = {};
                    this.spy();
                    this.spy.call({});
                    this.spy.call(object);
                    this.spy.call(window);

                    assert(this.spy.calledOn(object));
                });
            });
        }

        it("returns false if not called on object", function () {
            var object = {};
            this.spy.call(object);
            this.spy();

            assert.isFalse(this.spy.calledOn({}));
        });

        it("is true if called with matcher that returns true", function () {
            var matcher = sinonMatch(function () {
                return true;
            });
            this.spy();

            assert(this.spy.calledOn(matcher));
        });

        it("is false if called with matcher that returns false", function () {
            var matcher = sinonMatch(function () {
                return false;
            });
            this.spy();

            assert.isFalse(this.spy.calledOn(matcher));
        });

        it("invokes matcher.test with given object", function () {
            var expected = {};
            var actual;
            this.spy.call(expected);

            this.spy.calledOn(sinonMatch(function (value) {
                actual = value;
            }));

            assert.same(actual, expected);
        });
    });

    describe(".alwaysCalledOn", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false prior to calling the spy", function () {
            assert.isFalse(this.spy.alwaysCalledOn({}));
        });

        it("is true if called with thisValue once", function () {
            var object = {};
            this.spy.call(object);

            assert(this.spy.alwaysCalledOn(object));
        });

        it("is true if called with thisValue many times", function () {
            var object = {};
            this.spy.call(object);
            this.spy.call(object);
            this.spy.call(object);
            this.spy.call(object);

            assert(this.spy.alwaysCalledOn(object));
        });

        it("is false if called with another object atleast once", function () {
            var object = {};
            this.spy.call(object);
            this.spy.call(object);
            this.spy.call(object);
            this.spy();
            this.spy.call(object);

            assert.isFalse(this.spy.alwaysCalledOn(object));
        });

        it("is false if never called with expected object", function () {
            var object = {};
            this.spy();
            this.spy();
            this.spy();

            assert.isFalse(this.spy.alwaysCalledOn(object));
        });
    });

    describe(".calledWithNew", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false if spy wasn't called", function () {
            assert.isFalse(this.spy.calledWithNew());
        });

        it("is true if called with new", function () {
            var result = new this.spy(); // eslint-disable-line no-unused-vars, new-cap

            assert(this.spy.calledWithNew());
        });

        it("is true if called with new on custom constructor", function () {
            function MyThing() {}
            MyThing.prototype = {};
            var ns = { MyThing: MyThing };
            createSpy(ns, "MyThing");

            var result = new ns.MyThing(); // eslint-disable-line no-unused-vars
            assert(ns.MyThing.calledWithNew());
        });

        it("is false if called as function", function () {
            this.spy();

            assert.isFalse(this.spy.calledWithNew());
        });

        if (typeof window !== "undefined") {
            describe("in browser", function () {
                it("is true if called with new at least once", function () {
                    var object = {};
                    this.spy();
                    var a = new this.spy(); // eslint-disable-line no-unused-vars, new-cap
                    this.spy(object);
                    this.spy(window);

                    assert(this.spy.calledWithNew());
                });
            });
        }

        it("is true newed constructor returns object", function () {
            function MyThing() {
                return {};
            }
            var object = { MyThing: MyThing };
            createSpy(object, "MyThing");

            var result = new object.MyThing(); // eslint-disable-line no-unused-vars

            assert(object.MyThing.calledWithNew());
        });

        var applyableNatives = (function () {
            try {
                console.log.apply({}, []); // eslint-disable-line no-console
                return true;
            } catch (e) {
                return false;
            }
        }());
        if (applyableNatives) {
            describe("spied native function", function () {
                it("is false when called on spied native function", function () {
                    var log = { info: console.log }; // eslint-disable-line no-console
                    createSpy(log, "info");

                    // by logging an empty string, we're not polluting the test console output
                    log.info("");

                    assert.isFalse(log.info.calledWithNew());
                });
            });
        }
    });

    describe(".alwaysCalledWithNew", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("is false if spy wasn't called", function () {
            assert.isFalse(this.spy.alwaysCalledWithNew());
        });

        it("is true if always called with new", function () {
            /*eslint-disable no-unused-vars, new-cap*/
            var result = new this.spy();
            var result2 = new this.spy();
            var result3 = new this.spy();
            /*eslint-enable no-unused-vars, new-cap*/

            assert(this.spy.alwaysCalledWithNew());
        });

        it("is false if called as function once", function () {
            /*eslint-disable no-unused-vars, new-cap*/
            var result = new this.spy();
            var result2 = new this.spy();
            /*eslint-enable no-unused-vars, new-cap*/
            this.spy();

            assert.isFalse(this.spy.alwaysCalledWithNew());
        });
    });

    describe(".thisValues", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("contains one object", function () {
            var object = {};
            this.spy.call(object);

            assert.equals(this.spy.thisValues, [object]);
        });

        it("stacks up objects", function () {
            function MyConstructor() {}
            var objects = [{}, [], new MyConstructor(), { id: 243 }];
            this.spy();
            this.spy.call(objects[0]);
            this.spy.call(objects[1]);
            this.spy.call(objects[2]);
            this.spy.call(objects[3]);

            assert.equals(this.spy.thisValues, [this].concat(objects));
        });
    });

    describe(".calledWith", spyCalledTests("calledWith"));
    describe(".calledWithMatch", spyCalledTests("calledWithMatch"));

    describe(".calledWithMatchSpecial", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("checks substring match", function () {
            this.spy("I like it");

            assert(this.spy.calledWithMatch("like"));
            assert.isFalse(this.spy.calledWithMatch("nope"));
        });

        it("checks for regexp match", function () {
            this.spy("I like it");

            assert(this.spy.calledWithMatch(/[a-z ]+/i));
            assert.isFalse(this.spy.calledWithMatch(/[0-9]+/));
        });

        it("checks for partial object match", function () {
            this.spy({ foo: "foo", bar: "bar" });

            assert(this.spy.calledWithMatch({ bar: "bar" }));
            assert.isFalse(this.spy.calledWithMatch({ same: "same" }));
        });
    });

    describe(".alwaysCalledWith", spyAlwaysCalledTests("alwaysCalledWith"));
    describe(".alwaysCalledWithMatch", spyAlwaysCalledTests("alwaysCalledWithMatch"));

    describe(".alwaysCalledWithMatchSpecial", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("checks true", function () {
            this.spy(true);

            assert(this.spy.alwaysCalledWithMatch(true));
            assert.isFalse(this.spy.alwaysCalledWithMatch(false));
        });

        it("checks false", function () {
            this.spy(false);

            assert(this.spy.alwaysCalledWithMatch(false));
            assert.isFalse(this.spy.alwaysCalledWithMatch(true));
        });

        it("checks substring match", function () {
            this.spy("test case");
            this.spy("some test");
            this.spy("all tests");

            assert(this.spy.alwaysCalledWithMatch("test"));
            assert.isFalse(this.spy.alwaysCalledWithMatch("case"));
        });

        it("checks regexp match", function () {
            this.spy("1");
            this.spy("2");
            this.spy("3");

            assert(this.spy.alwaysCalledWithMatch(/[123]/));
            assert.isFalse(this.spy.alwaysCalledWithMatch(/[12]/));
        });

        it("checks partial object match", function () {
            this.spy({ a: "a", b: "b" });
            this.spy({ c: "c", b: "b" });
            this.spy({ b: "b", d: "d" });

            assert(this.spy.alwaysCalledWithMatch({ b: "b" }));
            assert.isFalse(this.spy.alwaysCalledWithMatch({ a: "a" }));
        });
    });

    describe(".neverCalledWith", spyNeverCalledTests("neverCalledWith"));
    describe(".neverCalledWithMatch", spyNeverCalledTests("neverCalledWithMatch"));

    describe(".neverCalledWithMatchSpecial", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("checks substring match", function () {
            this.spy("a test", "b test");

            assert(this.spy.neverCalledWithMatch("a", "a"));
            assert(this.spy.neverCalledWithMatch("b", "b"));
            assert(this.spy.neverCalledWithMatch("b", "a"));
            assert.isFalse(this.spy.neverCalledWithMatch("a", "b"));
        });

        it("checks regexp match", function () {
            this.spy("a test", "b test");

            assert(this.spy.neverCalledWithMatch(/a/, /a/));
            assert(this.spy.neverCalledWithMatch(/b/, /b/));
            assert(this.spy.neverCalledWithMatch(/b/, /a/));
            assert.isFalse(this.spy.neverCalledWithMatch(/a/, /b/));
        });

        it("checks partial object match", function () {
            this.spy({ a: "test", b: "test" });

            assert(this.spy.neverCalledWithMatch({ a: "nope" }));
            assert(this.spy.neverCalledWithMatch({ c: "test" }));
            assert.isFalse(this.spy.neverCalledWithMatch({ b: "test" }));
        });
    });

    describe(".args", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("contains real arrays", function () {
            this.spy();

            assert.isArray(this.spy.args[0]);
        });

        it("contains empty array when no arguments", function () {
            this.spy();

            assert.equals(this.spy.args, [[]]);
        });

        it("contains array with first call's arguments", function () {
            this.spy(1, 2, 3);

            assert.equals(this.spy.args, [[1, 2, 3]]);
        });

        it("stacks up arguments in nested array", function () {
            var objects = [{}, [], { id: 324 }];
            this.spy(1, objects[0], 3);
            this.spy(1, 2, objects[1]);
            this.spy(objects[2], 2, 3);

            assert.equals(this.spy.args, [
                [1, objects[0], 3],
                [1, 2, objects[1]],
                [objects[2], 2, 3]
            ]);
        });
    });

    describe(".calledWithExactly", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("returns false for partial match", function () {
            this.spy(1, 2, 3);

            assert.isFalse(this.spy.calledWithExactly(1, 2));
        });

        it("returns false for missing arguments", function () {
            this.spy(1, 2, 3);

            assert.isFalse(this.spy.calledWithExactly(1, 2, 3, 4));
        });

        it("returns true for exact match", function () {
            this.spy(1, 2, 3);

            assert(this.spy.calledWithExactly(1, 2, 3));
        });

        it("matchs by strict comparison", function () {
            this.spy({}, []);

            assert.isFalse(this.spy.calledWithExactly({}, [], null));
        });

        it("returns true for one exact match", function () {
            var object = {};
            var array = [];
            this.spy({}, []);
            this.spy(object, []);
            this.spy(object, array);

            assert(this.spy.calledWithExactly(object, array));
        });

        it("returns true when all properties of an object argument match", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert(this.spy.calledWithExactly({a: 1, b: 2, c: 3}));
        });

        it("returns false when a property of an object argument is set to undefined", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2, c: undefined}));
        });

        it("returns false when a property of an object argument is set to a different value", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2, c: "blah"}));
        });

        it("returns false when an object argument has a different property/value pair", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2, foo: "blah"}));
        });

        it("returns false when property of Object argument is set to undefined and has a different name", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2, foo: undefined}));
        });

        it("returns false when any properties of an object argument aren't present", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2}));
        });

        it("returns false when an object argument has extra properties", function () {
            this.spy({a: 1, b: 2, c: 3});

            assert.isFalse(this.spy.calledWithExactly({a: 1, b: 2, c: 3, d: 4}));
        });
    });

    describe(".alwaysCalledWithExactly", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
        });

        it("returns false for partial match", function () {
            this.spy(1, 2, 3);

            assert.isFalse(this.spy.alwaysCalledWithExactly(1, 2));
        });

        it("returns false for missing arguments", function () {
            this.spy(1, 2, 3);

            assert.isFalse(this.spy.alwaysCalledWithExactly(1, 2, 3, 4));
        });

        it("returns true for exact match", function () {
            this.spy(1, 2, 3);

            assert(this.spy.alwaysCalledWithExactly(1, 2, 3));
        });

        it("returns false for excess arguments", function () {
            this.spy({}, []);

            assert.isFalse(this.spy.alwaysCalledWithExactly({}, [], null));
        });

        it("returns false for one exact match", function () {
            var object = {};
            var array = [];
            this.spy({}, []);
            this.spy(object, []);
            this.spy(object, array);

            assert(this.spy.alwaysCalledWithExactly(object, array));
        });

        it("returns true for only exact matches", function () {
            var object = {};
            var array = [];

            this.spy(object, array);
            this.spy(object, array);
            this.spy(object, array);

            assert(this.spy.alwaysCalledWithExactly(object, array));
        });

        it("returns false for no exact matches", function () {
            var object = {};
            var array = [];

            this.spy(object, array, null);
            this.spy(object, array, undefined);
            this.spy(object, array, "");

            assert.isFalse(this.spy.alwaysCalledWithExactly(object, array));
        });
    });

    describe(".threw", function () {
        beforeEach(function () {
            this.spy = createSpy.create();

            this.spyWithTypeError = createSpy.create(function () {
                throw new TypeError();
            });

            this.spyWithStringError = createSpy.create(function () {
                throw "error";
            });
        });

        it("returns exception thrown by function", function () {
            var err = new Error();

            var spy = createSpy.create(function () {
                throw err;
            });

            try {
                spy();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(spy.threw(err));
        });

        it("returns false if spy did not throw", function () {
            this.spy();

            assert.isFalse(this.spy.threw());
        });

        it("returns true if spy threw", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.threw());
        });

        it("returns true if string type matches", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.threw("TypeError"));
        });

        it("returns false if string did not match", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert.isFalse(this.spyWithTypeError.threw("Error"));
        });

        it("returns false if spy did not throw specified error", function () {
            this.spy();

            assert.isFalse(this.spy.threw("Error"));
        });

        it("returns true if string matches", function () {
            try {
                this.spyWithStringError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(this.spyWithStringError.threw("error"));
        });

        it("returns false if strings do not match", function () {
            try {
                this.spyWithStringError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert.isFalse(this.spyWithStringError.threw("not the error"));
        });
    });

    describe(".alwaysThrew", function () {
        beforeEach(function () {
            this.spy = createSpy.create();

            this.spyWithTypeError = createSpy.create(function () {
                throw new TypeError();
            });
        });

        it("returns true when spy threw", function () {
            var err = new Error();

            var spy = createSpy.create(function () {
                throw err;
            });

            try {
                spy();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(spy.alwaysThrew(err));
        });

        it("returns false if spy did not throw", function () {
            this.spy();

            assert.isFalse(this.spy.alwaysThrew());
        });

        it("returns true if spy threw", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.alwaysThrew());
        });

        it("returns true if string type matches", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.alwaysThrew("TypeError"));
        });

        it("returns false if string did not match", function () {
            try {
                this.spyWithTypeError();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert.isFalse(this.spyWithTypeError.alwaysThrew("Error"));
        });

        it("returns false if spy did not throw specified error", function () {
            this.spy();

            assert.isFalse(this.spy.alwaysThrew("Error"));
        });

        it("returns false if some calls did not throw", function () {
            var callCount = 0;

            this.spy = createSpy(function () {
                callCount += 1;
                if (callCount === 1) {
                    throw new Error("throwing on first call");
                }
            });

            try {
                this.spy();
            } catch (e) {} // eslint-disable-line no-empty

            this.spy();

            assert.isFalse(this.spy.alwaysThrew());
        });

        it("returns true if all calls threw", function () {
            try {
                this.spyWithTypeError();
            } catch (e1) {} // eslint-disable-line no-empty

            try {
                this.spyWithTypeError();
            } catch (e2) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.alwaysThrew());
        });

        it("returns true if all calls threw same type", function () {
            try {
                this.spyWithTypeError();
            } catch (e1) {} // eslint-disable-line no-empty

            try {
                this.spyWithTypeError();
            } catch (e2) {} // eslint-disable-line no-empty

            assert(this.spyWithTypeError.alwaysThrew("TypeError"));
        });
    });

    describe(".exceptions", function () {
        beforeEach(function () {
            this.spy = createSpy.create();
            var error = this.error = {};

            this.spyWithTypeError = createSpy.create(function () {
                throw error;
            });
        });

        it("contains exception thrown by function", function () {
            try {
                this.spyWithTypeError();
            } catch (e) {} // eslint-disable-line no-empty

            assert.equals(this.spyWithTypeError.exceptions, [this.error]);
        });

        it("contains undefined entry when function did not throw", function () {
            this.spy();

            assert.equals(this.spy.exceptions.length, 1);
            refute.defined(this.spy.exceptions[0]);
        });

        it("stacks up exceptions and undefined", function () {
            var calls = 0;
            var err = this.error;

            var spy = createSpy.create(function () {
                calls += 1;

                if (calls % 2 === 0) {
                    throw err;
                }
            });

            spy();

            try {
                spy();
            } catch (e1) {} // eslint-disable-line no-empty

            spy();

            try {
                spy();
            } catch (e2) {} // eslint-disable-line no-empty

            spy();

            assert.equals(spy.exceptions.length, 5);
            refute.defined(spy.exceptions[0]);
            assert.equals(spy.exceptions[1], err);
            refute.defined(spy.exceptions[2]);
            assert.equals(spy.exceptions[3], err);
            refute.defined(spy.exceptions[4]);
        });
    });

    describe(".returned", function () {
        it("returns true when no argument", function () {
            var spy = createSpy.create();
            spy();

            assert(spy.returned());
        });

        it("returns true for undefined when no explicit return", function () {
            var spy = createSpy.create();
            spy();

            assert(spy.returned(undefined));
        });

        it("returns true when returned value once", function () {
            var values = [{}, 2, "hey", function () {}];
            var spy = createSpy.create(function () {
                return values[spy.callCount];
            });

            spy();
            spy();
            spy();
            spy();

            assert(spy.returned(values[3]));
        });

        it("returns false when value is never returned", function () {
            var values = [{}, 2, "hey", function () {}];
            var spy = createSpy.create(function () {
                return values[spy.callCount];
            });

            spy();
            spy();
            spy();
            spy();

            assert.isFalse(spy.returned({ id: 42 }));
        });

        it("returns true when value is returned several times", function () {
            var object = { id: 42 };
            var spy = createSpy.create(function () {
                return object;
            });

            spy();
            spy();
            spy();

            assert(spy.returned(object));
        });

        it("compares values deeply", function () {
            var object = { deep: { id: 42 } };
            var spy = createSpy.create(function () {
                return object;
            });

            spy();

            assert(spy.returned({ deep: { id: 42 } }));
        });

        it("compares values strictly using match.same", function () {
            var object = { id: 42 };
            var spy = createSpy.create(function () {
                return object;
            });

            spy();

            assert.isFalse(spy.returned(sinonMatch.same({ id: 42 })));
            assert(spy.returned(sinonMatch.same(object)));
        });
    });

    describe(".returnValues", function () {
        it("contains undefined when function does not return explicitly", function () {
            var spy = createSpy.create();
            spy();

            assert.equals(spy.returnValues.length, 1);
            refute.defined(spy.returnValues[0]);
        });

        it("contains return value", function () {
            var object = { id: 42 };

            var spy = createSpy.create(function () {
                return object;
            });

            spy();

            assert.equals(spy.returnValues, [object]);
        });

        it("contains undefined when function throws", function () {
            var spy = createSpy.create(function () {
                throw new Error();
            });

            try {
                spy();
            } catch (e) {} // eslint-disable-line no-empty

            assert.equals(spy.returnValues.length, 1);
            refute.defined(spy.returnValues[0]);
        });

        it("contains the created object for spied constructors", function () {
            var Spy = createSpy.create(function () { });

            var result = new Spy();

            assert.equals(Spy.returnValues[0], result);
        });

        it("contains the return value for spied constructors that explicitly return objects", function () {
            var Spy = createSpy.create(function () {
                return { isExplicitlyCreatedValue: true };
            });

            var result = new Spy();

            assert.isTrue(result.isExplicitlyCreatedValue);
            assert.equals(Spy.returnValues[0], result);
        });

        it("contains the created object for spied constructors that explicitly return primitive values", function () {
            var Spy = createSpy.create(function () {
                return 10;
            });

            var result = new Spy();

            refute.equals(result, 10);
            assert.equals(Spy.returnValues[0], result);
        });

        it("stacks up return values", function () {
            var calls = 0;

            /*eslint consistent-return: "off"*/
            var spy = createSpy.create(function () {
                calls += 1;

                if (calls % 2 === 0) {
                    return calls;
                }
            });

            spy();
            spy();
            spy();
            spy();
            spy();

            assert.equals(spy.returnValues.length, 5);
            refute.defined(spy.returnValues[0]);
            assert.equals(spy.returnValues[1], 2);
            refute.defined(spy.returnValues[2]);
            assert.equals(spy.returnValues[3], 4);
            refute.defined(spy.returnValues[4]);
        });
    });

    describe(".calledBefore", function () {
        beforeEach(function () {
            this.spy1 = createSpy();
            this.spy2 = createSpy();
        });

        it("is function", function () {
            assert.isFunction(this.spy1.calledBefore);
        });

        it("returns true if first call to A was before first to B", function () {
            this.spy1();
            this.spy2();

            assert(this.spy1.calledBefore(this.spy2));
        });

        it("compares call order of calls directly", function () {
            this.spy1();
            this.spy2();

            assert(this.spy1.getCall(0).calledBefore(this.spy2.getCall(0)));
        });

        it("returns false if not called", function () {
            this.spy2();

            assert.isFalse(this.spy1.calledBefore(this.spy2));
        });

        it("returns true if other not called", function () {
            this.spy1();

            assert(this.spy1.calledBefore(this.spy2));
        });

        it("returns false if other called first", function () {
            this.spy2();
            this.spy1();
            this.spy2();

            assert(this.spy1.calledBefore(this.spy2));
        });
    });

    describe(".calledAfter", function () {
        beforeEach(function () {
            this.spy1 = createSpy();
            this.spy2 = createSpy();
        });

        it("is function", function () {
            assert.isFunction(this.spy1.calledAfter);
        });

        it("returns true if first call to A was after first to B", function () {
            this.spy2();
            this.spy1();

            assert(this.spy1.calledAfter(this.spy2));
        });

        it("compares calls directly", function () {
            this.spy2();
            this.spy1();

            assert(this.spy1.getCall(0).calledAfter(this.spy2.getCall(0)));
        });

        it("returns false if not called", function () {
            this.spy2();

            assert.isFalse(this.spy1.calledAfter(this.spy2));
        });

        it("returns false if other not called", function () {
            this.spy1();

            assert.isFalse(this.spy1.calledAfter(this.spy2));
        });

        it("returns false if other called last", function () {
            this.spy2();
            this.spy1();
            this.spy2();

            assert.isFalse(this.spy1.calledAfter(this.spy2));
        });
    });

    describe(".firstCall", function () {
        it("is undefined by default", function () {
            var spy = createSpy();

            assert.isNull(spy.firstCall);
        });

        it("is equal to getCall(0) result after first call", function () {
            var spy = createSpy();

            spy();

            var call0 = spy.getCall(0);
            assert.equals(spy.firstCall.callId, call0.callId);
            assert.same(spy.firstCall.spy, call0.spy);
        });

        it("is equal to getCall(0) after first call when control flow has continued after invocation", function () {
            var spy;

            function runAsserts() {
                var call0 = spy.getCall(0);
                assert.equals(spy.firstCall.callId, call0.callId);
                assert.same(spy.firstCall.spy, call0.spy);
            }

            spy = createSpy(runAsserts);

            spy();
        });

        it("is tracked even if exceptions are thrown", function () {
            var spy = createSpy(function () {
                throw "an exception";
            });

            try {
                spy();
            }
            catch (e) {} // eslint-disable-line no-empty

            refute.isNull(spy.firstCall);
        });

        it("has correct returnValue", function () {
            var spy = createSpy(function () {
                return 42;
            });

            spy();

            assert.equals(spy.firstCall.returnValue, 42);
            assert(spy.firstCall.returned(42));
        });

        it("has correct exception", function () {
            var err = new Error();
            var spy = createSpy(function () {
                throw err;
            });

            try {
                spy();
            }
            catch (e) {} // eslint-disable-line no-empty

            assert.same(spy.firstCall.exception, err);
            assert(spy.firstCall.threw(err));
        });

    });

    describe(".secondCall", function () {
        it("is null by default", function () {
            var spy = createSpy();

            assert.isNull(spy.secondCall);
        });

        it("stills be null after first call", function () {
            var spy = createSpy();
            spy();

            assert.isNull(spy.secondCall);
        });

        it("is equal to getCall(1) result after second call", function () {
            var spy = createSpy();

            spy();
            spy();

            var call1 = spy.getCall(1);
            assert.equals(spy.secondCall.callId, call1.callId);
            assert.same(spy.secondCall.spy, call1.spy);
        });
    });

    describe(".thirdCall", function () {
        it("is undefined by default", function () {
            var spy = createSpy();

            assert.isNull(spy.thirdCall);
        });

        it("stills be undefined after second call", function () {
            var spy = createSpy();
            spy();
            spy();

            assert.isNull(spy.thirdCall);
        });

        it("is equal to getCall(1) result after second call", function () {
            var spy = createSpy();

            spy();
            spy();
            spy();

            var call2 = spy.getCall(2);
            assert.equals(spy.thirdCall.callId, call2.callId);
            assert.same(spy.thirdCall.spy, call2.spy);
        });
    });

    describe(".lastCall", function () {
        it("is undefined by default", function () {
            var spy = createSpy();

            assert.isNull(spy.lastCall);
        });

        it("is same as firstCall after first call", function () {
            var spy = createSpy();

            spy();

            assert.same(spy.lastCall.callId, spy.firstCall.callId);
            assert.same(spy.lastCall.spy, spy.firstCall.spy);
        });

        it("is same as secondCall after second call", function () {
            var spy = createSpy();

            spy();
            spy();

            assert.same(spy.lastCall.callId, spy.secondCall.callId);
            assert.same(spy.lastCall.spy, spy.secondCall.spy);
        });

        it("is same as thirdCall after third call", function () {
            var spy = createSpy();

            spy();
            spy();
            spy();

            assert.same(spy.lastCall.callId, spy.thirdCall.callId);
            assert.same(spy.lastCall.spy, spy.thirdCall.spy);
        });

        it("is equal to getCall(3) result after fourth call", function () {
            var spy = createSpy();

            spy();
            spy();
            spy();
            spy();

            var call3 = spy.getCall(3);
            assert.equals(spy.lastCall.callId, call3.callId);
            assert.same(spy.lastCall.spy, call3.spy);
        });

        it("is equal to getCall(4) result after fifth call", function () {
            var spy = createSpy();

            spy();
            spy();
            spy();
            spy();
            spy();

            var call4 = spy.getCall(4);
            assert.equals(spy.lastCall.callId, call4.callId);
            assert.same(spy.lastCall.spy, call4.spy);
        });
    });

    describe(".getCalls", function () {
        it("returns an empty Array by default", function () {
            var spy = createSpy();

            assert.isArray(spy.getCalls());
            assert.equals(spy.getCalls().length, 0);
        });

        it("is analogous to using getCall(n)", function () {
            var spy = createSpy();

            spy();
            spy();

            assert.equals(spy.getCalls(), [spy.getCall(0), spy.getCall(1)]);
        });
    });

    describe(".callArg", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.callArg);
        });

        it("invokes argument at index for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            spy(1, 2, callback);
            spy(3, 4, callback);

            spy.callArg(2);

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
        });

        it("throws if argument at index is not a function", function () {
            var spy = createSpy();
            spy();

            assert.exception(function () {
                spy.callArg(1);
            }, "TypeError");
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();

            try {
                spy.callArg(0);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot call arg since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");

            try {
                spy.callArg(0);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot call arg since it was not yet invoked.");
            }
        });

        it("throws if index is not a number", function () {
            var spy = createSpy();
            spy();

            assert.exception(function () {
                spy.callArg("");
            }, "TypeError");
        });

        it("passs additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            spy(callback);

            spy.callArg(0, "abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
        });
    });

    describe(".callArgOn", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.callArgOn);
        });

        it("invokes argument at index for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };
            spy(1, 2, callback);
            spy(3, 4, callback);

            spy.callArgOn(2, thisObj);

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
            assert(callback.alwaysCalledOn(thisObj));
        });

        it("throws if argument at index is not a function", function () {
            var spy = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };
            spy();

            assert.exception(function () {
                spy.callArgOn(1, thisObj);
            }, "TypeError");
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.callArgOn(0, thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot call arg since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.callArgOn(0, thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot call arg since it was not yet invoked.");
            }
        });

        it("throws if index is not a number", function () {
            var spy = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };
            spy();

            assert.exception(function () {
                spy.callArg("", thisObj);
            }, "TypeError");
        });

        it("pass additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            var thisObj = { name1: "value1", name2: "value2" };
            spy(callback);

            spy.callArgOn(0, thisObj, "abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
            assert(callback.calledOn(thisObj));
        });
    });

    describe(".callArgWith", function () {
        it("is alias for callArg", function () {
            var spy = createSpy();

            assert.same(spy.callArgWith, spy.callArg);
        });
    });

    describe(".callArgOnWith", function () {
        it("is alias for callArgOn", function () {
            var spy = createSpy();

            assert.same(spy.callArgOnWith, spy.callArgOn);
        });
    });

    describe(".yield", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.yield);
        });

        it("invokes first function arg for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            spy(1, 2, callback);
            spy(3, 4, callback);

            spy.yield();

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();

            try {
                spy.yield();
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot yield since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");

            try {
                spy.yield();
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot yield since it was not yet invoked.");
            }
        });

        it("passs additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            spy(callback);

            spy.yield("abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
        });
    });

    describe(".invokeCallback", function () {
        it("is alias for yield", function () {
            var spy = createSpy();

            assert.same(spy.invokeCallback, spy.yield);
        });
    });

    describe(".yieldOn", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.yieldOn);
        });

        it("invokes first function arg for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };
            spy(1, 2, callback);
            spy(3, 4, callback);

            spy.yieldOn(thisObj);

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
            assert(callback.alwaysCalledOn(thisObj));
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.yieldOn(thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot yield since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.yieldOn(thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot yield since it was not yet invoked.");
            }
        });

        it("pass additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            var thisObj = { name1: "value1", name2: "value2" };
            spy(callback);

            spy.yieldOn(thisObj, "abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
            assert(callback.calledOn(thisObj));
        });
    });

    describe(".yieldTo", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.yieldTo);
        });

        it("invokes first function arg for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            spy(1, 2, { success: callback });
            spy(3, 4, { success: callback });

            spy.yieldTo("success");

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();

            try {
                spy.yieldTo("success");
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot yield to 'success' since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");

            try {
                spy.yieldTo("success");
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot yield to 'success' since it was not yet invoked.");
            }
        });

        it("throws readable message for symbol when spy was not yet invoked", function () {
            if (typeof Symbol === "function") {
                var spy = createSpy();

                try {
                    spy.yieldTo(Symbol());
                } catch (e) {
                    assert.equals(e.message, "spy cannot yield to 'Symbol()' since it was not yet invoked.");
                }
            }
        });

        it("pass additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            spy({ test: callback });

            spy.yieldTo("test", "abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
        });
    });

    describe(".yieldToOn", function () {
        it("is function", function () {
            var spy = createSpy();

            assert.isFunction(spy.yieldToOn);
        });

        it("invokes first function arg for all calls", function () {
            var spy = createSpy();
            var callback = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };
            spy(1, 2, { success: callback });
            spy(3, 4, { success: callback });

            spy.yieldToOn("success", thisObj);

            assert(callback.calledTwice);
            assert(callback.alwaysCalledWith());
            assert(callback.alwaysCalledOn(thisObj));
        });

        it("throws if spy was not yet invoked", function () {
            var spy = createSpy();
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.yieldToOn("success", thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "spy cannot yield to 'success' since it was not yet invoked.");
            }
        });

        it("includes spy name in error message", function () {
            var api = { someMethod: function () {} };
            var spy = createSpy(api, "someMethod");
            var thisObj = { name1: "value1", name2: "value2" };

            try {
                spy.yieldToOn("success", thisObj);
                throw new Error();
            } catch (e) {
                assert.equals(e.message, "someMethod cannot yield to 'success' since it was not yet invoked.");
            }
        });

        it("throws readable message for symbol when spy was not yet invoked", function () {
            if (typeof Symbol === "function") {
                var spy = createSpy();
                var thisObj = { name1: "value1", name2: "value2" };

                try {
                    spy.yieldToOn(Symbol(), thisObj);
                } catch (e) {
                    assert.equals(e.message, "spy cannot yield to 'Symbol()' since it was not yet invoked.");
                }
            }
        });

        it("pass additional arguments", function () {
            var spy = createSpy();
            var callback = createSpy();
            var array = [];
            var object = {};
            var thisObj = { name1: "value1", name2: "value2" };
            spy({ test: callback });

            spy.yieldToOn("test", thisObj, "abc", 123, array, object);

            assert(callback.calledWith("abc", 123, array, object));
            assert(callback.calledOn(thisObj));
        });
    });

    describe(".reset", function () {
        it("return same object", function () {
            var spy = createSpy();
            var reset = spy.reset();

            assert(reset === spy);
        });

        it("throws if called during spy invocation", function () {
            var spy = createSpy(function () {
                spy.reset();
            });

            assert.exception(function () {
                spy();
            }, "InvalidResetException");
        });
    });

    describe(".length", function () {
        it("is zero by default", function () {
            var spy = createSpy();

            assert.equals(spy.length, 0);
        });

        it("matches the function length", function () {
            var api = { someMethod: function (a, b, c) {} }; // eslint-disable-line no-unused-vars
            var spy = createSpy(api, "someMethod");

            assert.equals(spy.length, 3);
        });
    });
});