Do not allow creation of groups with empty names

Gemfile

@@ -92,6 +92,7 @@ group :development, :test do
   gem 'rake'
   gem 'puma'
   gem 'rspec-rails', '~> 3.9'
+  gem 'rspec-its', '~> 1.3'
   gem 'factory_bot_rails', require: false
   gem 'faker'
   gem 'capybara'

Gemfile.lock

@@ -388,6 +388,9 @@ GEM
     rspec-expectations (3.9.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
+    rspec-its (1.3.0)
+      rspec-core (>= 3.0.0)
+      rspec-expectations (>= 3.0.0)
     rspec-mocks (3.9.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
@@ -556,6 +559,7 @@ DEPENDENCIES
   redcarpet
   redis
   rolify (~> 5.2)
+  rspec-its (~> 1.3)
   rspec-rails (~> 3.9)
   ruby-progressbar
   sanitize

app/models/group.rb

@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 class Group < ApplicationRecord
   belongs_to :user
   has_many :group_members, dependent: :destroy
 
+  validates :name, length: { minimum: 1 }
   validates :display_name, length: { maximum: 30 }
 
   before_validation do

spec/models/group_spec.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe(Group, type: :model) do
+  let(:user) { FactoryBot.build(:user) }
+
+  describe 'name mangling' do
+    subject do
+      Group.new(user: user, display_name: display_name).tap(&:validate)
+    end
+
+    {
+      'great group' => 'great-group',
+      'followers' => '-followers-',
+      '  followers  ' => '-followers-',
+      "  the game  \t\nyes" => 'the-game-yes',
+
+      # not nice, but this is just the way it is:
+      "\u{1f98a} :3" => '3',
+      "\u{1f98a}" => ''
+    }.each do |display_name, expected_name|
+      context "when display name is #{display_name.inspect}" do
+        let(:display_name) { display_name }
+
+        its(:name) { should eq expected_name }
+      end
+    end
+  end
+
+  describe 'validations' do
+    subject do
+      Group.new(user: user, display_name: display_name).validate
+    end
+
+    context "when display name is 'great group' (valid)" do
+      let(:display_name) { 'great group' }
+
+      it { is_expected.to be true }
+    end
+
+    context "when display name is '1' (valid)" do
+      let(:display_name) { '1' }
+
+      it { is_expected.to be true }
+    end
+
+    context 'when display name is the letter E 621 times (invalid, too long)' do
+      let(:display_name) { 'E' * 621 }
+
+      it { is_expected.to be false }
+    end
+
+    context 'when display name is an empty string (invalid, as `name` would be empty)' do
+      let(:display_name) { '' }
+
+      it { is_expected.to be false }
+    end
+
+    context "when display name is \u{1f98a} (invalid, as `name` would be empty)" do
+      let(:display_name) { "\u{1f98a}" }
+
+      it { is_expected.to be false }
+    end
+  end
+end

spec/rails_helper.rb

@@ -8,6 +8,7 @@ abort("The Rails environment is running in production mode!") if Rails.env.produ
 require "spec_helper"
 require "rspec/rails"
 # Add additional requires below this line. Rails is not loaded until this point!
+require "rspec/its"
 require "devise"
 require "capybara/rails"
 require "capybara/rspec"