Adding test for version api endpoint (#495)

version_test.go

+package gitlab
+
+import (
+	"fmt"
+	"net/http"
+	"reflect"
+	"testing"
+)
+
+func TestGetVersion(t *testing.T) {
+	mux, server, client := setup()
+	defer teardown(server)
+
+	mux.HandleFunc("/api/v4/version",
+		func(w http.ResponseWriter, r *http.Request) {
+			testMethod(t, r, "GET")
+			fmt.Fprint(w, `{"version":"11.3.4-ee", "revision":"14d3a1d"}`)
+		})
+
+	version, _, err := client.Version.GetVersion()
+	if err != nil {
+		t.Errorf("Version.GetVersion returned error: %v", err)
+	}
+
+	want := &Version{Version: "11.3.4-ee", Revision: "14d3a1d"}
+	if !reflect.DeepEqual(want, version) {
+		t.Errorf("Version.GetVersion returned %+v, want %+v", version, want)
+	}
+}