PHPフレームワークLaravel5.6でCRUD～UPDATE&DELETE編

    public function edit($id) {
        $data = [];
        $data['categories'] = self::CATEGORY_LIST;
        $data['test'] = Test::find($id);
        return view('test/edit', $data);
    }

@extends('layouts.app')

@section('content')
<div class="container">

  <div class="panel panel-default">

    <h2 class="text-white bg-secondary">変更</h2>
    <a href="/test"><button class="btn btn-primary">一覧に戻る</button></a>

    <form action="/test/{{ $test->id }}" method="POST">
      @csrf
      @method('PUT')
      <div class="form-group">
        <label>タイトル</label>
        <input type="text" name="title" value="{{ old('title', $test->title) }}" class="form-control">
        @if($errors->has('title'))
        <span class="text-danger">{{ $errors->first('title') }}</span>
        @endif
      </div>
      <div class="form-group">
        <label>カテゴリ</label>
        <select name="category" class="form-control">
          <option value="">選択してください</option>
        @foreach ($categories as $key => $category)
          <option value="{{ $key }}"@if($key == old('category', $test->category)) selected @endif>{{ $category }}</option>
        @endforeach
        </select>
        @if($errors->has('category'))
        <span class="text-danger">{{ $errors->first('category') }}</span>
        @endif
      </div>
      <div class="form-group">
        <label>説明</label>
        <textarea name="description" class="form-control">{{ old('description', $test->description) }}</textarea>
        @if($errors->has('description'))
        <span class="text-danger">{{ $errors->first('description') }}</span>
        @endif
      </div>
      <button type="submit" class="btn btn-primary">変更</button>
    </form>

  </div>

</div>
@endsection

    public function update(Request $request, $id) {

        // バリデーション
        $this->validate($request, 
            [
                'title' => 'required',
                'category' => 'required',
                'description' => 'required',
            ],
            [
                'title.required' => 'タイトルを入力してください',
                'category.required' => 'カテゴリを選択してください',
                'description.required' => '説明を入力してください',
            ]
        );
        // 
        $test = Test::find($id);
        $test->fill($request->all())->save();
        return redirect('test');

    }

    public function destroy($id)
    {
        Test::find($id)->delete();
        return redirect('test');
    }