Testing Cookie Writes in Golang

cookie_read_test.go

func TestSetCookie(t *testing.T) {
  // Create a new HTTP Recorder (implements http.ResponseWriter)
  recorder := httptest.NewRecorder()
  
  // Drop a cookie on the recorder.
  http.SetCookie(recorder, &http.Cookie{Name: "test", Value: "expected"})
  
  // Copy the Cookie over to a new Request
  request := &http.Request{Header: http.Header{"Cookie": recorder.HeaderMap["Set-Cookie"]}}
  
  // Extract the dropped cookie from the request.
  cookie, err := request.Cookie("test")

  require.NoError(t, err, "Failed to read 'test' Cookie: %v, err)
  require.Equal(t, cookie.Value, "expected")
}

This solution is not adapter for new version of golang. You will have :

recorder.HeaderMap is deprecated: HeaderMap exists for historical compatibility and should not be used. To access the headers returned by a handler, use the Response.Header map as returned by the Result method.

You should use :
recorder.Result().Cookies()[0] as @mfhholmes mentionne.

You can get the value with : recorder.Result().Cookies()[0].Value