class Rails::Application

def asset_precompiled?(logical_path)

isn't precompiled and hence won't be available in production.
Called from asset helpers to alert you if you reference an asset URL that 
def asset_precompiled?(logical_path)
  precompiled_assets.include? logical_path
end

def precompiled_assets

request or test case.
boot time, but ensure we cache the list so we don't recompute it for each
Lazy-load the precompile list so we don't cause asset compilation at app 
def precompiled_assets
  @precompiled_assets ||= assets_manifest.find(config.assets.precompile).map(&:logical_path).to_set
end