How to unit test a function with a static call

Question

I have a function I am writing that uses the Doctrine DBAL system. This uses a static function to connect as follows:

$conn = \Doctrine\DBAL\DriverManager::getConnection($connectionParams, $config);

I want to unit test this functionality with a mock.

public function openNewConnection(string $database_name): Connection
{
       try {
            // some logic where I check the validity of the connection
            $this->connection = DriverManager::getConnection($connection_params, $config);
            break;
        } catch (Exception $e) {
            // catch the different errors that could be created
        }
    return $this->connection;
}

I cannot use dependency injection as a way round this as:

I am dynamically generating $connectionParams : I need to make the call here
there is no (proper) way to non statically call this function : I would just be moving the problem elsewhere

I've been working in phpunit, and I've also had a look at mockery. I don't really see how I am meant to make this work:

This mockery test doesn't work, but I'm unsure of how it should:

public function testConnect(): void
{
    // mocked connection return
    $mocked_connection = new Connection([], $this->driver);

    // use Mockery to simulate static call
    $driver_manager = Mockery::mock('alias:\Doctrine\DBAL\DriverManager');
    $driver_manager->shouldReceive('getConnection')
                   ->once()
                   ->andReturn($mocked_connection);

    $database = new Database($this->database_configuration_file);
    $database->openNewConnection('test_db_cluster_01');

    $this->assertEquals($mocked_connection, $database->getConnection());
}

From what I can see, the $database isn't even aware of $driver_manager, so I don't see how the mocking would happen.

Here's my question:

Is it even possible to test a function called statically like this?
If so, is mockery a/the way to do this?
If so, what is wrong with my above test?

(that's not an answer) Actually, you can use dependency injection in your case. Instead of calling DriverManager::getConnection() you can use $this->connectionFactory->getConnection($connectionParams). Now you can inject (and mock in tests) the $connectionFactory. — Ivan Kalita
Nope, because the $connectionParams are not externally known. The aim of the openNewConnection function is to parse over multiple connection parameters and connect. While I could factor the "connection bit" out to a separate function, it doesn't stop the fact that the connection is still static. I want to mock the static call. — elb98rm

Ivan Kalita Ivan Kalita · Accepted Answer · 2018-03-20T11:39:19

Yes, it is possible.
Yes, Mockery (as well as PHPUnit itself) can do this (using "fake autoloading"). Check this article for more information.
I didn't find any problems in your test. Please, check this repo. I tried to reproduce your problem, but everything goes OK.

How to unit test a function with a static call

1 Answers