当使用conn：sqlite value :: memory：而不是conn：mysql db：在phpunit.xml中测试时，一些测试开始失败？

I have already written many tests. All were passing in this config of phpunit.xml

<env name="DB_CONNECTION" value="mysql"/>
<env name="DB_DATABASE" value="testing"/>

But they were slow so I changed it to in-memory sqlite:

<env name="DB_CONNECTION" value="sqlite"/>
<env name="DB_DATABASE" value=":memory:"/>

This is very fast but gives error on some tests.

example:

/** @test */
public function a_user_can_create_a_post()
{

  $payload = [
     'title' => 'This is title',
     'body' => 'This is body',
  ];

        $this->actingAs($this->adminUser)
                        ->json('POST', '/post', $payload)
                        ->assertRedirect(route('post.index'))
                        ->assertSessionHas('message', 'Post Created!');
}

It gives 500 status code instead of redirect code. When I remove the json line and simply assert some path 200 then it works fine.

What is the problem ?