<!DOCTYPE html>
<html>

  <head>
    <title>Biodb</title>
    <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
    <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
    <%= csrf_meta_tags %>
  </head>

  <body>
  
    <header>
      <nav class="navbar navbar-default" role="navigation">
        <div class="container-fluid">

          <div class="navbar-header">
            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navbar-collapse-1">
              <span class="sr-only">Toggle navigation</span>
              <span class="icon-bar"></span>
              <span class="icon-bar"></span>
              <span class="icon-bar"></span>
            </button>
            <%= link_to 'Biodb', home_url, class: 'navbar-brand' %>
          </div>
        
          <div class="collapse navbar-collapse" id="navbar-collapse-1">
            <ul class="nav navbar-nav navbar-right">
              <% if current_user %>
                <li><%= link_to 'sign out', delete_session_path, :method => :delete %></li>
              <% end %>
            </ul>
            <% if current_user %>
              <p class="navbar-text navbar-right"><%= current_user.email %></p>
            <% end %>
          </div>

        </div>
      </nav>
    </header>

    <%= yield %>

  </body>

</html>

<!DOCTYPE html>
<html>

  <head>
    <title>Biodb</title>
    <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
    <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
    <%= csrf_meta_tags %>
  </head>

  <body>
  
    <header>
      <nav id="main-menu" class="navbar navbar-default" role="navigation">
        <div class="container-fluid">

          <div class="navbar-header">
            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#navbar-collapse-1">
              <span class="sr-only">Toggle navigation</span>
              <span class="icon-bar"></span>
              <span class="icon-bar"></span>
              <span class="icon-bar"></span>
            </button>
            <%= link_to 'Biodb', home_url, class: 'navbar-brand' %>
          </div>
        
          <div class="collapse navbar-collapse" id="navbar-collapse-1">
            <ul class="nav navbar-nav navbar-right">
              <% if current_user %>
                <li><%= link_to 'sign out', delete_session_path, :method => :delete %></li>
              <% end %>
            </ul>
            <% if current_user %>
              <p class="navbar-text navbar-right"><%= current_user.email %></p>
            <% end %>
          </div>

        </div>
      </nav>
    </header>

    <%= yield %>

  </body>

</html>

Add id='main-menu' to navbar to aid view testing
Add id='main-menu' to navbar to aid view testing
