测试修改话题报错：Unable to locate factory with name [default]？

vagrant@homestead:~/code/larabbs2$ phpunit
PHPUnit 6.5.12 by Sebastian Bergmann and contributors.

..E. 4 / 4 (100%)

Time: 2.75 seconds, Memory: 24.00MB

There was 1 error:

1) Tests\Feature\TopicApiTest::testUpdateTopic
InvalidArgumentException: Unable to locate factory with name [default] [Tests\Feature\Topic].

/home/vagrant/code/larabbs2/vendor/laravel/framework/src/Illuminate/Database/Eloquent/FactoryBuilder.php:248
/home/vagrant/code/larabbs2/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Concerns/GuardsAttributes.php:122
/home/vagrant/code/larabbs2/vendor/laravel/framework/src/Illuminate/Database/Eloquent/FactoryBuilder.php:260
/home/vagrant/code/larabbs2/vendor/laravel/framework/src/Illuminate/Database/Eloquent/FactoryBuilder.php:185
/home/vagrant/code/larabbs2/vendor/laravel/framework/src/Illuminate/Database/Eloquent/FactoryBuilder.php:148
/home/vagrant/code/larabbs2/tests/Feature/TopicApiTest.php:62
/home/vagrant/code/larabbs2/tests/Feature/TopicApiTest.php:40

ERRORS!
Tests: 4, Assertions: 7, Errors: 1.