creddit/spec/models/post_spec.rb

require 'rails_helper'

describe Post, type: :model do
  let(:post) { build(:post) }

  it { should belong_to(:user) }
  it { should belong_to(:subcreddit) }
  it { should have_many(:comments) }

  it { should delegate_method(:username).to(:user).with_prefix }

  context 'when adding a comment' do
    let(:post) { create(:post) }

    it 'should update the cache_counter for comments' do
      expect do
        create(:comment, post: post)
      end.to change { post.comments_count }.by(1)
    end
  end

  context 'with valid data' do
    it 'should be valid' do
      expect(post).to be_valid
    end

    it 'should allow blank content' do
      post.content = ''

      expect(post).to be_valid
    end

    it 'should allow a blank link' do
      post.link = ''

      expect(post).to be_valid
    end
  end

  context 'with invalid data' do
    it 'should not allow a blank title' do
      post.title = ''

      expect(post).to be_invalid
    end

    it 'should not allow a long title' do
      post.title = 'a' * 301

      expect(post).to be_invalid
    end

    it 'should not allow long content' do
      post.content = 'a' * 15001

      expect(post).to be_invalid
    end
  end

  context '#to_param' do
    it 'generates the correct param' do
      post.save

      expect(post.to_param).to eq("#{post.id}-#{post.title.parameterize}")
    end
  end

  context '#comments?' do
    let(:post) { create(:post) }

    context 'with comments' do
      before(:each) do
        create(:comment, post: post)
      end

      it 'should respond with true' do
        expect(post.comments?).to be(true)
      end
    end

    context 'without comments' do
      it 'should respond with false' do
        expect(post.comments?).to be(false)
      end
    end
  end
end