Category: Development (Page 4 of 18)

Jasmine is the default unit testing framework that I use when writing javascript, however my poor brain can’t always remember all the different ways of getting things to work. There are quite a number of cheat sheets out on the internet including:

• Err the Blog’s Cheat Sheet
• Toby Ho’s Cheat Sheet

They don’t quite cover all the examples as well. Here’s my contributions to demonstrate some of the common uses.

describe("jasmine", function () {

    describe("basic invocations", function () {

        var SampleDependency = function () {
            return {
                usefulMethod:function (firstParameter, secondParameter) {
                },
                anotherUsefulMethod:function () {
                }
            };
        };

        var Consumer = function (dependency) {
            return {
                run:function () {
                    dependency.usefulMethod("first", "second");
                },
                runSecondMethod:function () {
                    dependency.anotherUsefulMethod();
                },
                runWithRequiredCallback:function(callback) {
                    callback("an argument");
                }
            };
        };

        it("should spy on an existing function", function () {
            // given
            var dependency = new SampleDependency();
            spyOn(dependency, "usefulMethod");
            var consumer = new Consumer(dependency);

            // when
            consumer.run();

            // then
            expect(dependency.usefulMethod).toHaveBeenCalled();
            expect(dependency.usefulMethod).toHaveBeenCalledWith("first", "second");
            expect(dependency.usefulMethod).toHaveBeenCalledWith(jasmine.any(String), jasmine.any(String));
            expect(dependency.usefulMethod.callCount).toEqual(1);
            expect(dependency.usefulMethod.mostRecentCall.args).toEqual(["first", "second"]);
        });

        it("should demonstrate resetting of the spy", function () {
            // given
            var dependency = new SampleDependency();
            spyOn(dependency, "usefulMethod");
            dependency.usefulMethod();
            dependency.usefulMethod.reset();

            // when
            dependency.usefulMethod();

            // then
            expect(dependency.usefulMethod).toHaveBeenCalled();
            expect(dependency.usefulMethod.callCount).toEqual(1);
        });

        it("should demonstrate creating a spy object with prepopulated methods", function () {
            // given
            var dependency = jasmine.createSpyObj("dependency", ["usefulMethod", "anotherUsefulMethod"]);
            var consumer = new Consumer(dependency);

            // when
            consumer.run();
            consumer.runSecondMethod();

            // then
            expect(dependency.usefulMethod).toHaveBeenCalled();
            expect(dependency.anotherUsefulMethod).toHaveBeenCalled();
        });

        it("should demonstrate creating a stub object", function () {
            // given
            var dependency = jasmine.createSpyObj("dependency", ["usefulMethod", "anotherUsefulMethod"]);
            var consumer = new Consumer(dependency);
            var stubbedCallback = jasmine.createSpy("stub callback");


            // when
            consumer.runWithRequiredCallback(stubbedCallback);

            // then
            expect(stubbedCallback).toHaveBeenCalled();
            expect(stubbedCallback).toHaveBeenCalledWith("an argument");
        });
    });


    describe("returning a value", function () {
        var Dependency = function () {
            return {
                getMultiplier:function () {
                    return 10;
                }
            };
        };

        var Consumer = function (dependency) {
            return {
                calculateSomethingWithMultiplier:function (number) {
                    return number * dependency.getMultiplier();
                }
            };
        };

        it('should be correct', function () {
            // given
            var dependency = new Dependency();
            spyOn(dependency, "getMultiplier").andReturn(40);
            var consumer = new Consumer(dependency);

            // when
            var result = consumer.calculateSomethingWithMultiplier(3);

            // then
            expect(result).toEqual(120);
        });
    });


    it("should demonstrate creating a stub that returns a value", function () {
    });

    describe("creating a stub that calls a fake", function () {
        var Dependency = function () {
            return {
                request:function (callback) {
                }
            };
        };
        var Consumer = function (dependency) {
            var capturedValue = "";
            return {
                hardAtWork:function () {
                    dependency.request(function (value) {
                        capturedValue = value;
                    });
                },
                getCapturedValue:function () {
                    return capturedValue;
                }
            };
        };

        it('should demonstrate creating a stub function that does something interesting', function () {
            // given
            var dependency = new Dependency();
            spyOn(dependency, "request").andCallFake(function (callback) {
                callback("Controlled return value from callback");
            });
            var consumer = new Consumer(dependency);

            // when
            consumer.hardAtWork();

            // then
            expect(consumer.getCapturedValue()).toEqual("Controlled return value from callback");
        });

    });
});

I’ve been working on setting up the infrastructure for a mostly javascript based project, and we’ve been putting RequireJS into the codebase to help us manage the file dependencies instead of having to declare them within the page that is using them. As a concept, RequireJS is helping us keep different javascript modules apart in different files and let’s us assemble them.

RequireJS works by declaring dependencies and having the framework pull them in when you need them.

define(["aDependency"], function(theDependency) {
  // now I can do something with theDependency
  theDependency.aMethodOnIt();
})

This is pretty much how spring works, but the issue I have is that RequireJS manages the lifecycle of the javascript objects, so when you want to pass in a substitute for a test, you end up in a dilemma.

define(["aDependency"], function(theDependency) { // how do I get inject a different instance?
  // now I can do something with theDependency
  theDependency.aMethodOnIt();
})

Unsurprisingly a number of people wrote libraries such as testr which allow you to override the requirejs to inject different versions. Although very reasonable approaches, I find this approach a little bit smelly as you’re effectively patching a library you don’t own. The ruby community know the dangers of monkey patching too much, particularly those parts of a code base you cannot control and the potential issues you face when you try to upgrade.

Our current approach involves using RequireJS to manage the file/name dependencies, but for us to write javascript that allows us to control the instances of the objects that we want. Here’s an example:

dependency.js

define([], function () {
    return function () {
        return {
            doSomeWork:function () {
            }
        };
    };
});

consumer.js

define([], function () {
    return function (aDependency) {
        var dependency = aDependency;
        return {
            start:function () {
                dependency.doSomeWork();
            }
        };
    };
});

And then we control the lifecycle of the components and instances in the application using the following code.

main.js

define(["consumer", "dependency"], function (Consumer, Dependency) {
    var dependency = Dependency();
    var consumer = Consumer(dependency);
    consumer.start();
});

And our jasmine tests get to look like this:

requirejs = require('requirejs');

describe("consumer", function() {
    it("should ensure the dependency does some work", function() {
        // given
        var dependency = jasmine.createSpyObj("dependency", ["doSomeWork"]);
        var consumer = requirejs("consumer")(dependency);

        // when
        consumer.start();

        // then
        expect(dependency.doSomeWork).toHaveBeenCalled();
    });
});

This approach has been working out well, forcing us to manage the dependency and global hell that javascript global functions can quickly become. Thoughts? Please leave a comment.