Testing Guide

class ExampleTest extends TestCase
{
    public function testBasicTest()
    {
        UserRepository::partialMock()
            ->shouldReceive('index')
            ->andReturn(['data' => [],]);

        $this->withHeader('Accept', 'application/json')
            ->get('/api/restify/users')
            ->assertJsonStructure([
                'response' => 'data',
            ])->assertOk();
    }
}

So you can use the partialMock to get the partial mock instance of the repository, and then perform actions or expectations over it.