How to use PHPUnit for Mock testing in PHP development

In PHP development, testing is a very important link. Testing can greatly reduce the occurrence of errors and improve code quality. Mock testing is a form of testing that can simulate fake objects or data in order to test a specific function or scenario of our code.

PHPUnit is a very popular testing framework in PHP, which supports Mock testing. In this article, we will explore how to use PHPUnit for mock testing.

1. What is Mock testing

Before we begin, let’s first understand the concept of Mock testing. Mock testing is a type of simulation test that allows us to test without real dependencies.

For example, we are developing an e-commerce website that includes a shopping cart functionality. When conducting shopping cart testing, we need to test functions such as adding, deleting, and price calculations for items. However, these features may rely on other modules or external APIs. This makes our testing very difficult. If we need to conduct real testing, the testing cost will be very high.

Mock testing allows us to test without real dependencies. In the shopping cart test, we can use the Mock testing framework to create a mock product and use it in the test to test the addition, deletion, price calculation and other functions of the product. This way we can easily test the functionality of the shopping cart without requiring real items or an external API.

2. Use PHPUnit for Mock testing

Next, we will use the PHPUnit testing framework for Mock testing. In PHPUnit, we can use the PHPUnitFrameworkMockObjectMockBuilder class to create Mock objects. MockBuilder is a class in PHPUnit that can help us create Mock objects.

1. Create Mock objects

In PHPUnit, we can use MockBuilder to create Mock objects. We can create a mock object through MockBuilder and define its methods and properties. We can then use the Mock object to test our code.

For example, we need to simulate a product object in the shopping cart test. We can use MockBuilder to create a mock commodity object.

Code example:

use PHPUnitFrameworkTestCase;

class ShoppingCartTest extends TestCase
{
    public function testAddProduct()
    {
        // 创建 MockBuilder 对象
        $product = $this->getMockBuilder(Product::class)
            ->getMock();

        // 测试真实代码，使用假对象
        $cart = new ShoppingCart();
        $cart->addProduct($product);

        // 断言购物车中包含模拟的商品
        $this->assertTrue($cart->hasProduct($product));
    }
}

In this example code, we create a MockBuilder object to build a simulated product object (Product). Then, we use this object to perform the add product function of the shopping cart. Finally, we used the assertTrue() assertion to verify whether the shopping cart contains the product object we constructed.

2. Method definition and return value setting

We can simulate real objects or data by setting the methods and properties of the Mock object.

For example, we have a Person class, which has a sayHello() method, which can return a string "Hello".

Code example:

class Person {
    public function sayHello() {
        return "Hello";
    }
}

Now, we have a Greeting class whose method depends on the sayHello() method of the Person class. We can use MockBuilder to create a mock Person object and call the Greeting method in the test.

Code example:

use PHPUnitFrameworkTestCase;

class GreetingTest extends TestCase
{
    public function testSayHello()
    {
        // 创建 MockBuilder 对象
        $person = $this->getMockBuilder(Person::class)
            ->getMock();

        // 定义方法返回值
        $person->expects($this->any())
            ->method('sayHello')
            ->willReturn('Hello, Mock');

        // 测试真实代码，使用假对象
        $greeting = new Greeting($person);
        $this->assertEquals('Hello, Mock', $greeting->sayHello());
    }
}

In this example code, we create a MockBuilder object to build a mock Person object. Then, we define the return value of the sayHello() method of the Person object as "Hello, Mock". Finally, we used the object to execute Greeting's sayHello() method, and used assertEquals() to assert whether the method returned "Hello, Mock".

3. Method call verification

In PHPUnit, we can use Mock objects to verify method calls. We can use PHPUnit's expectations API to verify that the method was called.

For example, we have a Person class, which has a sayHello() method, which returns a string "Hello".

Code example:

class Person {
    public function sayHello() {
        return "Hello";
    }
}

Now, we have a Greeting class whose constructor requires a Person object and has a sayHello() method that depends on the SayHello() method of the Person class. We can use the expectations API to test whether the sayHello() method of the greeting class successfully calls the sayHello() method of the Person class.

Code example:

use PHPUnitFrameworkTestCase;

class GreetingTest extends TestCase
{
    public function testSayHello()
    {
        // 创建 MockBuilder 对象
        $person = $this->getMockBuilder(Person::class)
            ->getMock();

        // 验证方法是否被调用
        $person->expects($this->once())
            ->method('sayHello');

        // 测试真实代码，使用假对象
        $greeting = new Greeting($person);
        $greeting->sayHello();
    }
}

In this example code, we create a MockBuilder object to build a mock Person object. We then use the expectations API to verify whether the sayHello() method of the Person class was successfully called.

4. Mock test of constructor

In PHPUnit, we can use the getMock() method to simulate the instantiation process of a class and set the constructor and constructor parameters respectively.

For example, we have a Calculator class that has a constructor and an add method. In the constructor, we need to pass a number $a and $b. The add method adds a and b and returns the result.

Code Example:

class Calculator
{
    public function __construct($a, $b)
    {
        $this->a = $a;
        $this->b = $b;
    }

    public function add()
    {
        return $this->a + $this->b;
    }
}

Now, we have a CalculatorTest class that needs to test the add method of the Calculator class. We can use the getMock() method to simulate the creation process of the Calculator object and set the parameters of the constructor.

Code example:

use PHPUnitFrameworkTestCase;

class CalculatorTest extends TestCase
{
    public function testAdd()
    {
        // 创建 Mock 对象
        $calculator = $this->getMockBuilder(Calculator::class)
            ->disableOriginalConstructor()
            ->getMock();

        // 手动设置构造函数参数
        $calculator->expects($this->any())
            ->method('__construct')
            ->with(2, 3)
            ->willReturn(5);

        // 测试真实代码，使用假对象
        $this->assertEquals(5, $calculator->add());
    }
}

在这个示例代码中，我们创建了一个MockBuilder对象来构建一个模拟Calculator对象。然后，我们使用getMock()方法来模拟Calculator对象的创建过程，并使用disableOriginalConstructor()方法来禁用原始构造函数。接着，我们使用expects()方法来设置构造函数的参数，并在willReturn()方法中返回我们的期望值。

最后，我们使用assertEquals()断言来验证add()方法是否返回我们预期的值。

三、总结

Mock测试可以轻松地帮助我们在不需要真实依赖的情况下进行测试。在PHPUnit中，PHPUnitFrameworkMockObjectMockBuilder类可以帮助我们创建Mock对象并进行Mock测试。

在使用MockBuilder创建Mock对象时，我们可以设置需要模拟的属性和方法，包括方法的返回值和调用次数，甚至模拟构造函数。Mock测试可以使我们的测试更加简单和高效，并且隔离了我们的代码与外部依赖的测试。

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