Mock-object and dummy- (stub function) use in testing

Mock-object (from the English. Mock object , literally: "object-parody", "object-imitation", as well as "stand") - in object-oriented programming - the type of objects that implement the specified aspects of the simulated software environment. for example internet connection emulation or work with databases

A mock object is a concrete fictitious implementation of an interface intended solely for testing the interaction and for which a statement is expressed.

In procedural programming, a similar construction is called “dummy” (English is a stub). A function that yields a constant, or a random variable from a valid range of values.

Mock-objects are actively used in the development through testing.

During the use of Bocs, Dependency injection is often used.

PHP Laravel example

<? php

class QuestionsControllerTest extends TestCase {

protected $ questionMock;

public function setUp ()
{
// $ this-> questionMock = Mockery :: mock ('Question');

$ this-> questionMock = Mockery :: mock (Question :: class);

$ this-> app-> instance (Question :: class, $ this-> questionMock);
}

public function testQuestionIndex ()
{
$ this-> questionMock
-> shouldReceive ('latest')
-> once ();

$ this-> app-> instance ('Question', $ this-> questionMock);

$ this-> call ('GET', 'questions');
}

<? php namespace App \ Http \ Controllers;

use App \ Http \ Requests \ QuestionRequest;
use App \ Http \ Controllers \ Controller;

use App \ Question;

use Auth;
use Request;

class QuestionsController extends Controller {

protected $ question;

public function __construct (Question $ question)
{
$ this-> question = $ question;
}

public function index ()
{
$ questions = $ this-> question-> latest () -> get ();

return view ('questions.index', compact ('questions'));
}
...

launch

$ ./vendor/bin/phpunit tests / controllers / QuestionsControllerTest.php PHPUnit 4.5.0 by Sebastian Bergmann and contributors.

Time: 135 ms, Memory: 12.50Mb

A stub function (in programming) is a function that performs no meaningful action and returns an empty result or input data as it is. Same as the stub method.

Used by:

• For clarity, when designing the structure of application classes.
• Some functions may be “muted” for debugging other functions.
• To restrict access to certain fields of the class (for example, to the root of a tree).

An example of a stub function in the C language: