ExampleFactory.php

<?php

class ExampleFactory
{
    /**
     * @param DI $di
     */
    public function __invoke(DI $di)
    {
        $dependency = $di->get(Dependency::class);
        
        return new Example($dependency);
    }
}

ExampleFactoryTest.php

<?php

public function ExampleFactoryTest extends TestCase
{
    public function testReturnsExampleConcreteInstance()
    {
        $di = $this->getMock(DI::class);
        
        $factory = new ExampleFactory($di);
        
        $di->expects($this->once())
           ->method('get')
           ->with(Dependency::class)
           ->willReturn(
               $this->getMock(Dependency::class)
           );
        
        $this->assertInstanceOf(Example::class, $factory());
    }
}