Add tests for snippet services

Add Rspec tests for the new UpdateSnippetService and
CreateSnippetService classes.

spec/services/create_snippet_service_spec.rb

+require 'spec_helper'
+
+describe CreateSnippetService do
+  before do
+    @user = create :user
+    @admin = create :user, admin: true
+    @opts = {
+      title: 'Test snippet',
+      file_name: 'snippet.rb',
+      content: 'puts "hello world"',
+      visibility_level: Gitlab::VisibilityLevel::PRIVATE
+    }
+  end
+
+  context 'When public visibility is restricted' do
+    before do
+      allow_any_instance_of(ApplicationSetting).to(
+        receive(:restricted_visibility_levels).and_return(
+          [Gitlab::VisibilityLevel::PUBLIC]
+        )
+      )
+
+      @opts.merge!(visibility_level: Gitlab::VisibilityLevel::PUBLIC)
+    end
+
+    it 'non-admins should not be able to create a public snippet' do
+      snippet = create_snippet(nil, @user, @opts)
+      expect(snippet.errors.messages).to have_key(:visibility_level)
+      expect(snippet.errors.messages[:visibility_level].first).to(
+        match('Public visibility has been restricted')
+      )
+    end
+
+    it 'admins should be able to create a public snippet' do
+      snippet = create_snippet(nil, @admin, @opts)
+      expect(snippet.errors.any?).to be_falsey
+      expect(snippet.visibility_level).to eq(Gitlab::VisibilityLevel::PUBLIC)
+    end
+  end
+
+  def create_snippet(project, user, opts)
+    CreateSnippetService.new(project, user, opts).execute
+  end
+end

spec/services/update_snippet_service_spec.rb

+require 'spec_helper'
+
+describe UpdateSnippetService do
+  before do
+    @user = create :user
+    @admin = create :user, admin: true
+    @opts = {
+      title: 'Test snippet',
+      file_name: 'snippet.rb',
+      content: 'puts "hello world"',
+      visibility_level: Gitlab::VisibilityLevel::PRIVATE
+    }
+  end
+
+  context 'When public visibility is restricted' do
+    before do
+      allow_any_instance_of(ApplicationSetting).to(
+        receive(:restricted_visibility_levels).and_return(
+          [Gitlab::VisibilityLevel::PUBLIC]
+        )
+      )
+
+      @snippet = create_snippet(@project, @user, @opts)
+      @opts.merge!(visibility_level: Gitlab::VisibilityLevel::PUBLIC)
+    end
+
+    it 'non-admins should not be able to update to public visibility' do
+      old_visibility = @snippet.visibility_level
+      update_snippet(@project, @user, @snippet, @opts)
+      expect(@snippet.errors.messages).to have_key(:visibility_level)
+      expect(@snippet.errors.messages[:visibility_level].first).to(
+        match('Public visibility has been restricted')
+      )
+      expect(@snippet.visibility_level).to eq(old_visibility)
+    end
+
+    it 'admins should be able to update to pubic visibility' do
+      old_visibility = @snippet.visibility_level
+      update_snippet(@project, @admin, @snippet, @opts)
+      expect(@snippet.visibility_level).not_to eq(old_visibility)
+      expect(@snippet.visibility_level).to eq(Gitlab::VisibilityLevel::PUBLIC)
+    end
+  end
+
+  def create_snippet(project, user, opts)
+    CreateSnippetService.new(project, user, opts).execute
+  end
+
+  def update_snippet(project = nil, user, snippet, opts)
+    UpdateSnippetService.new(project, user, snippet, opts).execute
+  end
+end