1-TestCase.php

<?php

class TestCase extends Illuminate\Foundation\Testing\TestCase {
  
  // ...
  
  public function appMock($name)
  {
    $mock = Mockery::mock($name);
    App::instance($name, $mock);
    return $mock;
  }

}

2-ControllerTest.php

<?php

class JobsControllerTest extends TestCase
{
  
  public function testSomething()
  {
    $this->appMock('JobRepositoryInterface')
      ->shouldReceive('all')->once()
      ->andReturn('lorem');
      
    $this->call('GET', 'jobs');
    
    // ...
  }
  
}