add test for deepMerge panic

pr211_2_test.go

@@ -0,0 +1,25 @@
+package mergo
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+type transformer struct {
+}
+
+func (s *transformer) Transformer(t reflect.Type) func(dst, src reflect.Value) error {
+	return nil
+}
+
+func Test_deepMergeTransformerInvalidDestination(t *testing.T) {
+	foo := time.Time{}
+	src := reflect.ValueOf(foo)
+	deepMerge(reflect.Value{}, src, make(map[uintptr]*visit), 0, &Config{
+		Transformers: &transformer{},
+	})
+	// this test is intentionally not asserting on anything, it's sole
+	// purpose to verify deepMerge doesn't panic when a transformer is
+	// passed and the destination is invalid.
+}