add test function

binding/multipart_form_mapping.go

@@ -15,6 +15,7 @@ import (
 type multipartRequest http.Request
 
 var _ setter = (*multipartRequest)(nil)
+var ConstructionFailure = false
 
 // TrySet tries to set a value by the multipart request with the binding a form file
 func (r *multipartRequest) TrySet(value reflect.Value, field reflect.StructField, key string, opt setOptions) (isSetted bool, err error) {
@@ -48,6 +49,11 @@ func setByMultipartFormFile(value reflect.Value, field reflect.StructField, file
 			}
 			defer fd.Close()
 			c, err := ioutil.ReadAll(fd)
+
+			if ConstructionFailure {
+				err = errors.New("test use")
+			}
+
 			if err != nil {
 				return false, err
 			}

binding/multipart_form_mapping_test.go

@@ -32,6 +32,24 @@ func TestFormMultipartBindingOneFileToBytesFail1(t *testing.T) {
 	assert.Error(t, err)
 }
 
+func TestFormMultipartBindingOneFileToBytesFail2(t *testing.T) {
+	var test struct {
+		Voice []byte `form:"voice"`
+	}
+
+	file := testFile{"voice", "test.pcm", []byte("pcm pcm pcm")}
+	req := createRequestMultipartFiles(t, file)
+
+	ConstructionFailure = true
+
+	err := req.ParseMultipartForm(3)
+	assert.NoError(t, err)
+
+	err = mappingByPtr(&test, (*multipartRequest)(req), "form")
+	assert.Error(t, err)
+	ConstructionFailure = false
+}
+
 func TestFormMultipartBindingOneFileToBytesArray(t *testing.T) {
 	var test struct {
 		Voice []byte `form:"voice"`