Test Double

Tired of remembering the difference between mocks, partials, and spies in Mockery? I am, which is why I created double() - a simple helper method to make using Mockery easier.

When writing tests I don't want to think about the differences between fakes, mocks, and spies. I just to create a generic test double and focus on writing my test. This generalization is common in other testing frameworks such as RSpec, td.js, and more.

Installation

To install the latest version of the double() helper, run the command:

composer require --dev jasonmccreary/test-double

Usage

Anytime you need to create a test double simply call double()

By default, double() returns an object that will allow you to stub methods as well as verify method calls.

<?php
$td = double();

$td->shouldReceive('someMethod')->andReturn(5);

$td->someMethod();       // returns 5
$td->unstubbedMethod();  // returns null, does not throw an exception

$td->anotherMethod();
$td->shouldHaveReceived('anotherMethod');

In Mockery, this test double is equivalent to Mockery::mock()->shouldIgnoreMissing() or, in recent versions, Mockery::spy().

You can also pass double() a reference to a class or interface. This will create a test object that extends the class or implements the interface. This allows the double to pass any type hints or type checking in your implementation.

<?php
$td = double(Str::class);

$td->shouldReceive('length')->andReturn(5);

$td->length();           // 5
$td->substr(1, 3);       // null

$td instanceof Str;      // true

$td->shouldHaveReceived('substr')->with(1, 3);

Finally, double() accepts a second argument of passthru. By default, passthru is false. When set to true, the test object will pass any method calls through to the underlying object.

In Mockery, this is equivalent to Mockery::mock(Number::class)->shouldDeferMissing().

<?php
class Number
{
    public function one()
    {
        return 1;
    }

    public function random()
    {
        return 5;
    }
}

$td = double(Number::class, true);

$td->shouldReceive('random')->andReturn(21);

$td->random();            // 21
$td->one();               // 1

$td instanceof Number;    // true

$td->shouldHaveReceived('one');

Note: passthru can only be used when creating a test double with a class reference as that is the only time an underlying implementation exists.

In the end, double() is an opinionated way to create test objects for your underlying code. If it does not meet your needs, you can always create a Mockery::mock() directly. However, doing so is likely a smell you're testing your implementation in a way that does not reflect real world behavior. Remember, double() returns an object which implements the MockeryInterface. So it can be treated as any other Mockery::mock() object.