Factor out error type checks

server/testing_utils.go

@@ -1,6 +1,7 @@
 package weavedns
 
 import (
+	"reflect"
 	"testing"
 )
 
@@ -15,3 +16,17 @@ func assertStatus(t *testing.T, got int, wanted int, desc string) {
 		t.Fatalf("Expected %s %d but got %d", desc, wanted, got)
 	}
 }
+
+func assertErrorInterface(t *testing.T, got interface{}, wanted interface{}, desc string) {
+	got_t, wanted_t := reflect.TypeOf(got), reflect.TypeOf(wanted).Elem()
+	if !got_t.Implements(wanted_t) {
+		t.Fatalf("Expected %s but got %s (%s)", wanted_t.String(), got_t.String(), desc)
+	}
+}
+
+func assertErrorType(t *testing.T, got interface{}, wanted interface{}, desc string) {
+	got_t, wanted_t := reflect.TypeOf(got), reflect.TypeOf(wanted).Elem()
+	if got_t != wanted_t {
+		t.Fatalf("Expected %s but got %s (%s)", wanted_t.String(), got_t.String(), desc)
+	}
+}