tasks.nameに必須と桁数のバリデーション処理を入れる

app/models/task.rb

@@ -2,4 +2,6 @@
 
 class Task < ApplicationRecord
   enum status: { waiting: 1, work_in_progress: 2, completed: 3 }
+
+  validates :name, presence: true, length: { maximum: 20 }
 end

db/migrate/20190531002052_change_column_to_task.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class ChangeColumnToTask < ActiveRecord::Migration[5.2]
+  def change
+    change_column :tasks, :name, :string, limit: 20
+  end
+end

db/schema.rb

@@ -12,9 +12,9 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20_190_521_053_254) do
+ActiveRecord::Schema.define(version: 20_190_531_002_052) do
   create_table 'tasks', options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8', force: :cascade do |t|
-    t.string 'name', null: false
+    t.string 'name', limit: 20, null: false
     t.text 'description'
     t.integer 'status', limit: 1, default: 1, null: false, unsigned: true
     t.datetime 'created_at', null: false

spec/models/task_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Task, type: :model do
+  describe '#save' do
+    let(:task) { described_class.new(name: 'hoge') }
+
+    it 'creates records in task' do
+      task.save
+      expect(Task.count).to eq(1)
+      expect(task.errors.count).to eq(0)
+    end
+
+    context 'nameへの入力がない' do
+      let(:task) { described_class.new(name: nil) }
+
+      it '必須のエラーメッセージが出ること' do
+        task.save
+
+        expect(Task.count).to eq(0)
+        expect(task.errors[:name]).to include('を入力してください')
+      end
+    end
+
+    context 'nameへ21文字以上の入力があると' do
+      let(:task) { described_class.new(name: '１２３４５６７８９０１２３４５６７８９０a') }
+
+      it '桁数超過のエラーメッセージが出ること' do
+        task.save
+
+        expect(Task.count).to eq(0)
+        expect(task.errors[:name]).to include('は20文字以内で入力してください')
+      end
+    end
+  end
+end