Refactoring: variable names, adding tests and http constants

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

gateway/tests/cors_test.go

@@ -0,0 +1,36 @@
+package tests
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/openfaas/faas/gateway/handlers"
+)
+
+type customHandler struct {
+}
+
+func (h customHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+}
+
+func Test_HeadersAdded(t *testing.T) {
+	rr := httptest.NewRecorder()
+	handler := customHandler{}
+	host := "store.openfaas.com"
+
+	decorated := handlers.DecorateWithCORS(handler, host)
+	request, _ := http.NewRequest(http.MethodGet, "/", nil)
+	decorated.ServeHTTP(rr, request)
+
+	actual := rr.Header().Get("Access-Control-Allow-Origin")
+	if actual != host {
+		t.Errorf("Access-Control-Allow-Origin: want: %s got: %s", host, actual)
+	}
+
+	actualMethods := rr.Header().Get("Access-Control-Allow-Methods")
+	if actualMethods != "GET" {
+		t.Errorf("Access-Control-Allow-Methods: want: %s got: %s", "GET", actualMethods)
+	}
+
+}