如何使用phpunit和laravel测试上传图像

Question

我想用phpunit和laravel测试上传图片过程。 我在控制器中的功能如下：

public function store(Request $request){
        $validator = Validator::make($request->all() , [
            'name' => 'required|string|max:300',
            'icon' => 'nullable|image'
        ]);
        if($validator->fails()){
            return response()->json([
                'status' => 422,
                'message' => 'validation_error_occurred',
                'entire' => [
                    'errors' => $validator->errors()->all()
                ]
            ] , 422);
        }

    $category = new StoreCategory();
    $category->name = $request->name;
    if($request->hasFile('icon')){
        $imgName = uniqid() . '.' . $request->icon->getClientOriginalExtension();
        $request->icon->move(public_path('/store-categories-image') , $imgName);
        $category->icon = $imgName;
    }
    $category->save();
    return response()->json([
        'status' => 200,
        'message' => 'category_stored' ,
        'entire' => [
            'category' => $category
        ]
    ] , 200);
}

我的phpunit测试如下：

public function testSaveCategory(){
    $admin = factory(Admin::class)->create();
    $token = $admin->createToken('loginToken')->accessToken;
    $category = factory(StoreCategory::class)->create();
    $this->json('POST' , '/admin-api/store-category' , [
        'name' => $category->name,
        'icon' => UploadedFile::fake()->image('icon.png')
    ] , [
        'Accept' => 'application/json',
        'Authorization' => 'Bearer ' . $token
    ])
        ->assertStatus(200)
        ->assertJson([
            'status' => 200,
            'message' => 'category_stored',
        ])
        ->assertJsonStructure([
            'entire' => [
                'category' => ['id' , 'icon' , 'name' , 'deleted' , 'created_at' , 'updated_at']
            ]
        ]);
}

但是，当我在命令行中运行phpunit命令时，测试失败并得到以下消息：

Excepted status code 200 but received 500. 当我在邮递员中运行我的api时，它成功返回状态200。

出什么问题了？