Add tests for group and project access requests

gitlab_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
@@ -58,6 +59,10 @@ func testBody(t *testing.T, r *http.Request, want string) {
 	}
 }
 
+func errorOption(*http.Request) error {
+	return errors.New("OptionFunc returns an error")
+}
+
 func TestNewClient(t *testing.T) {
 	c := NewClient(nil, "")
 	expectedBaseURL := defaultBaseURL + apiVersionPath