PHP Fatal error: Class Mock_LoggerInterface contains 8 abstract >methods and must therefore be declared abstract or implement the remaining

Question

Preconditions (*)

1. Magento 2.3.1 upgraded from Magento 2.3.0
2. Php 7.2.15
3. OS : Ubuntu 18.04 Bionic
4. Phpstorm 2019.1.1
5. Evnironemnt : Magento development
6. PHPUnit 6.5.0
7. magento/magento2-functional-testing-framework": "~2.3.13"

Steps to reproduce (*)

• Follow the code to reproduce the error

Error

PHP Fatal error: Class Mock_LoggerInterface_a49cf619 contains 8 abstract >methods and must therefore be declared abstract or implement the remaining >methods (Psr\Log\LoggerInterface::emergency, Psr\Log>\LoggerInterface::alert, Psr\Log\LoggerInterface::critical, ...) in /var/www/html/myproject/vendor/phpunit/phpunit-mock-objects>/src/Generator.php(264) : eval()'d code on line 1

My class code is given below

use Psr\Log\LoggerInterface;

class Foo {


    private $logger;
    private $myclassObject;

    public function __construct(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }
    public function Bar ()
    {
      // some code
      $logger->debug ('debug message')

    }
}

My Test Class Code is

use PHPUnit\Framework\TestCase;

class FooTest extends TestCase
{

    private $logger;
    public function setUp()
    {
        $this->logger = $this->getMockBuilder('\Psr\Log\LoggerInterface')
            ->setMethods(null)
            ->getMock();

        $this->logger->expects($this->any())
            ->method('debug')
            ->willReturn('Message Logged');
    }

    $this->myclassObject = $this->getMockBuilder('MyVendor\MyModule\Model\Foo')
    ->setMethods(['__construct'])        
    ->setConstructorArgs(['$logger'])
    ->disableOriginalConstructor()
    ->getMock();

    public function testBar()
    {

        $this->assertEquals($expected_result,$this->myclassObject->Bar());
    }
}

I'm expecting a successful unit test.

Answer 1

You get this error because you are trying to create a mock for an interface via mock builder which should be used to create mocks for classes. There are multiple ways how to create a mock for the interface:

use Psr\Log\LoggerInterface;
//...
$this->logger = $this->getMockForAbstractClass(LoggerInterface::class)

or mock all interface's methods:

$this->logger = $this->getMockBuilder(LoggerInterface::class)
    ->setMethods([
        'emergency',
        'alert',
        'critical',
        'error',
        'warning',
        'notice',
        'info',
        'debug',
        'log'
    ])
    ->getMock();

Also, it's better to use namespace instead of string representation and avoid the usage of FQCN.

Calling expects($this->any()) doesn't make any sense as it will be called by default.