PHP中的测试替身：如何使用Mock对象进行单元测试

class OrderService {
    private $paymentGateway;

    public function __construct(PaymentGateway $paymentGateway) {
        $this->paymentGateway = $paymentGateway;
    }

    public function processOrder(Order $order) {
        if ($order->getTotal() > 100 && $this->paymentGateway->isAvailable()) {
            return $this->paymentGateway->processPayment($order->getTotal());
        }
        return false;
    }
}

class Order {
  private $total;

  public function __construct(float $total) {
    $this->total = $total;
  }

  public function getTotal(): float {
    return $this->total;
  }
}

interface PaymentGateway {
    public function isAvailable(): bool;
    public function processPayment(float $amount): bool;
}

use PHPUnit\Framework\TestCase;

class OrderServiceTest extends TestCase {
    public function testProcessOrder_PaymentSuccessful() {
        // 1. 创建 Mock 对象
        $paymentGatewayMock = $this->createMock(PaymentGateway::class);

        // 2. 设置 Mock 对象的期望行为
        $paymentGatewayMock->method('isAvailable')
                           ->willReturn(true);
        $paymentGatewayMock->method('processPayment')
                           ->willReturn(true);

        // 3. 创建 OrderService 实例，并注入 Mock 对象
        $orderService = new OrderService($paymentGatewayMock);
        $order = new Order(150.0);

        // 4. 执行被测代码
        $result = $orderService->processOrder($order);

        // 5. 断言结果
        $this->assertTrue($result);
    }

    public function testProcessOrder_PaymentFailed() {
        $paymentGatewayMock = $this->createMock(PaymentGateway::class);
        $paymentGatewayMock->method('isAvailable')->willReturn(false);

        $orderService = new OrderService($paymentGatewayMock);
        $order = new Order(150.0);

        $result = $orderService->processOrder($order);

        $this->assertFalse($result);
    }
}

public function testProcessOrder_PaymentCalledWithCorrectAmount() {
    $paymentGatewayMock = $this->createMock(PaymentGateway::class);

    $paymentGatewayMock->expects($this->once())
                       ->method('processPayment')
                       ->with($this->equalTo(150.0))
                       ->willReturn(true);

    $orderService = new OrderService($paymentGatewayMock);
    $order = new Order(150.0);
    $orderService->processOrder($order);
}