Why is ridicule necessary in the unit test?

What is ridicule?


Prologue: When you look up the noun Mock in the dictionary you will find that one of the definitions of the word is something made as an imitation .

Mocking is mainly used in unit testing. An object to be tested can have dependencies on other (complex) objects. To isolate the behavior of the object, you want to replace the other objects with mocks that simulate the behavior of the real objects. This is useful when it is impractical to unit test the real objects.

In short, mocking creates objects that simulate the behavior of real objects.

Sometimes you might want between To mock and Distinguish stumps . There may be some disagreement on this subject, but my definition of a stub is a "minimal" simulated object. The stub implements just enough behavior for the object under test to run the test.

A mock is like a stub, but the test also verifies that the object under test is calling the mock as expected. Part of the test is to verify that the model has been used correctly.

For example, you can stump a database by implementing a simple in-memory structure for storing records. The object to be tested can then read records and write them to the database stub so that it can run the test. This could test behavior of the object unrelated to the database, and the database stub would only be included for the test to run.

Instead, if you want to verify that the object under test is writing certain data to the database, then you have to mock the database. Your test would then contain statements about what was written to the database mock.

Other answers explain what ridicule is. Indulge yourself with different Examples through the Cause thing . And believe me, it's actually a lot easier than you think.

tl; dr It is an instance of the original class. It has other data injected into it, so avoid testing the injected parts and just focus on testing the Implementation details Your class / functions.

A simple example:

As you can see, I am not testing LineA which means I am not validating the input parameters. I am not checking that num1, num2 are an integer. I have no claims against it.

I'm just testing if LineB (my implementation ) has given the ridiculed values ​​and does what I expect.

Obviously this can get a lot more complex in the actual word. The parameters can be a custom object such as a person, an address, or the implementation details can be more than a single one. But the logic of testing would be the same.

Non-coding example:

For example, suppose you are building a machine that identifies the type and brand name of electronic equipment used for airport security. The machine processes what it sees with its camera.

Now your manager comes in the door and asks you to unit test them.

Then, as a developer, you can either bring 1000 real objects like a MacBook Pro, Google Nexus, a banana, an iPad, etc. in front of you and test whether everything works.

But you can too mocked Use objects, e.g. B. an identical looking MacBook Pro (without real inner parts) or a plastic banana in front of it. You can save yourself investing in 1000 real laptops and rotting bananas.

The point is, you are not trying to test whether the banana is fake or not. Still testing whether the laptop is counterfeit or not. All you do is test that as soon as it sees a banana your computer would say, and for a MacBook Pro it would say:. For the machine, the result of its detection for fake / mocked electronics and real electronics should be the same

The above logic also applies to unit testing the actual code. This is a function that works with real values ​​that you go through real Inputs (and interactions) received or the to be ridiculed should work the same wayvalues ​​that you inject during the unit test. And just like protecting yourself from using a real banana or MacBook, unit testing (and taunting) saves you from having to do something that will cause your server to write a status code of 500, 403, 200, etc. return (forcing) Your server will only fire 500 if the server has failed while 200 has failed. It becomes difficult to run 100 network-oriented tests when you have to wait 10 seconds continuously between switching the server up and down. Instead, you inject / mock a response with status code 500, 200, 403, etc. and test your unit / function with an injected / mocked value.

Coding example:

Suppose you are writing an iOS application and you have network calls. Your job is Your Test application. Testing / identifying whether or not the network calls are working as expected is NOT YOUR RESPONSIBILITY. It is the responsibility of another party (server team) to test this. You need to remove this (network) dependency and still continue to test all of your code using the around you around is working .

A network call can return various status codes 404, 500, 200, 303, etc. with a JSON response.

Your app is assumed to be capable of all works (in the event of an error, your app should trigger the expected error). What you do with the mockery is that you create "imaginary - similar to real" network responses (like a 200 code with a JSON file) and test your code, without "Make the real network call and wait for your network answer". You can manually hardcode / return the network response for ALL types of network responses and see if your app is working as expected. (You take No way a 200 with wrong data on / test it as this is not your responsibility. You are responsible for Your Test the app with a correct 200. On a 400, 500 test that your app is throwing the correct error.)

This creation of the imaginary - similar to real - is called ridicule.

To this end can Your original code Not Use (your original code doesn't have the pre-inserted answers, does it?). you have to add something, insert / insert the normally unnecessary dummy data (or part of your class).

So you create an instance of the original class and add whatever you need (here is the network HTTP response, data OR if there is an error, pass the correct errorString, HTTPResponse), then test the mocked Class.

In short, ridicule means the , what you're testing, too simplify and to restrict and make you feed what a class depends on. In this example, you can avoid testing the Network is called , and instead test that your app works as expected with the injected outputs / responses - by mocking Classes

Of course, you test each network response separately.

One question I always had in mind was: The contracts / endpoints and basically the JSON response of my APIs are constantly being updated. How can I write unit tests that take this into account?

To explain this in more detail, let's say the model needs a key / field with the name. You test this and your test passes. 2 weeks later, the backend changes the name of the key to. Your tests still pass. Law? or not?

Is it the backend developer's responsibility to update the mocks? Should it be part of our agreement for them to provide updated tauntings?

The answer to the above problem is: unit testing + your development process as a client-side developer should / would get outdated mocked answers. If you ask me how Well the answer is:

Our actual app would fail (or not fail, but not behave as we should) without using updated APIs. If that fails, we will make changes to our development code. Which in turn causes our tests to fail ... which we need to correct. (If we want to do the TDD process correctly, we mustn't write any code over the field unless we write the test for it ... and see it fails, and then write the actual development code for it.)

All of this means that the backend doesn't have to say, “Hey, we've updated the mocks”. this happens in the end through your code development / debugging. ‌ّ Because everything is part of the development process! If the backend gives you the mocked answer for you, it's easier.

My whole point on this is that (if you can't automate updating the mocked API response) some human interaction is required, ie manual Updates to JSONs and brief meetings to make sure their values ​​are up to date will become part of your process

This section was written thanks to a casual discussion in our CocoaHead Meetup group

For iOS developers only:

A very good example of ridicule is this practical protocol-oriented lecture by Natasha Muraschev. Just skip to the 6:30 p.m. minute, although the slides may no longer be in sync with the actual video 🤷‍♂️

I really like this part from the transcript:

Since this is a test ... we want to make sure the function is called by as it can return and theoretically assign the function to a range of foods from anywhere . We have to make sure it is called;

There are many SO answers and good posts on the internet about ridicule. One place you might want to start is on Martin Fowler's post, Mocks Aren't Stubs, where he discusses lots of ideas to ridicule.

In a paragraph - Mocking is a special technique that allows a unit of code to be tested without relying on dependencies. In general, mocking differs from other methods in that mock objects, which are used to replace code dependencies, allow expectations to be set. A mock object knows how to call your code and how to react.

Your original question mentioned TypeMock, so I've left my answer to it below:

TypeMock is the name of a commercial mocking framework.

It has all of the functionality of the free mocking frameworks like RhinoMocks and Moq, plus some more powerful options.

Whether or not you need TypeMock is highly controversial - you can use free mocking libraries to do most of the mocking you could ever want, and many argue that the capabilities TypeMock offers can often turn you away from a well-encapsulated design.

As stated in another answer, "TypeMocking" is actually not a defined concept but can be understood as the kind of mockery that TypeMock offers by using the CLR Profiler to intercept .NET calls at runtime, making objects a lot can be falsified better (no requirements, e.g. needing interfaces or virtual methods).

Mock is a method / object that simulates the behavior of a real method / object in a controlled manner. Mock objects are used in unit testing.

Often a method to be tested calls other external services or methods contained therein. These are called dependencies. Once ridiculed, the dependencies behave as we defined them.

Since the dependencies are controlled by mocks, we can easily test the behavior of the method we coded. This is unit test.

What is the purpose of bogus objects?

Mocks vs stubs

Unit tests vs functional tests

Mocking generates pseudo-objects that simulate the behavior of real objects for testing

The purpose of mocking types is to separate dependencies in order to isolate the test on a particular entity. Stubs are simple surrogates, while mocks are surrogates that can verify usage. A mocking framework is a tool that you can use to generate stubs and mocks.

EDIT : Since the original wording mentions "Type Mocking", I got the impression that this was related to TypeMock. In my experience, the general term is just "mocking". Please ignore the following information specific to TypeMock.

TypeMock Isolator differs from most other mocking frameworks in that it makes my modifying IL work on the fly. This allows for types and instances to be mocked that most other frameworks cannot. In order to mock these types / instances with other frameworks, you need to provide your own abstractions and mock them.

TypeMock offers great flexibility at the expense of a clean runtime environment. As a side effect of the way TypeMock does its results, sometimes you get very strange results when you use TypeMock.

I would think using the TypeMock isolator mocking framework would be TypeMocking.

It's a tool that generates unit test mocks without writing your code with IoC in mind.

If your mock is a network requirement, another alternative is to use a real test server. With this service you can generate a request and answer for your tests. http://testerurl.com/

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