Refine error message when validating extension name (#845)

Signed-off-by: jack.wong <jack.wong@bytedance.com>
Co-authored-by: jack.wong <jack.wong@bytedance.com>

v2/event/extensions.go

@@ -50,7 +50,7 @@ func validateExtensionName(key string) error {
 
 	for _, c := range key {
 		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9')) {
-			return errors.New("bad key, CloudEvents attribute names MUST consist of lower-case letters ('a' to 'z') or digits ('0' to '9') from the ASCII character set")
+			return errors.New("bad key, CloudEvents attribute names MUST consist of lower-case letters ('a' to 'z'), upper-case letters ('A' to 'Z') or digits ('0' to '9') from the ASCII character set")
 		}
 	}
 	return nil

v2/event/extensions_test.go

@@ -0,0 +1,40 @@
+/*
+ Copyright 2021 The CloudEvents Authors
+ SPDX-License-Identifier: Apache-2.0
+*/
+
+package event
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestEvent_validateExtensionName(t *testing.T) {
+	testCases := map[string]struct {
+		key  string
+		want error
+	}{
+		"empty key": {
+			key:  "",
+			want: errors.New("bad key, CloudEvents attribute names MUST NOT be empty"),
+		},
+		"invalid character": {
+			key:  "invalid_key",
+			want: errors.New("bad key, CloudEvents attribute names MUST consist of lower-case letters ('a' to 'z'), upper-case letters ('A' to 'Z') or digits ('0' to '9') from the ASCII character set"),
+		},
+		"valid key": {
+			key:  "validkey123",
+			want: nil,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			err := validateExtensionName(tc.key)
+			if err != nil && err.Error() != tc.want.Error() || err == nil && tc.want != nil {
+				t.Errorf("unexpected error, expected: %v, actual: %v", tc.want, err)
+			}
+		})
+	}
+}