operator/pkg/util: unit test template

In this commit, we unit test template on parsing template functionality
on parsing and executing html templates with passed args.

Signed-off-by: Mohamed Awnallah <mohamedmohey2352@gmail.com>

operator/pkg/util/template_test.go

@@ -0,0 +1,82 @@
+/*
+Copyright 2024 The Karmada Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestParseTemplate(t *testing.T) {
+	tests := []struct {
+		name     string
+		template string
+		args     interface{}
+		want     []byte
+		wantErr  bool
+		errMsg   string
+	}{
+		{
+			name:     "ParseTemplate_WithMissingVariable_ParsingFailed",
+			template: "Hello, {{.Name}}!",
+			args:     struct{ Missing string }{Missing: "World"},
+			want:     nil,
+			wantErr:  true,
+			errMsg:   "error when executing template",
+		},
+		{
+			name:     "ParseTemplate_WithInvalidTemplateSyntax_ParsingFailed",
+			template: "Hello, {{.Name!",
+			args:     struct{ Name string }{Name: "World"},
+			want:     nil,
+			wantErr:  true,
+			errMsg:   "error when parsing template",
+		},
+		{
+			name:     "ParseTemplate_ValidTemplateWithVariable_ParsingSucceeded",
+			template: "Hello, {{.Name}}!",
+			args:     struct{ Name string }{Name: "World"},
+			want:     []byte("Hello, World!"),
+			wantErr:  false,
+		},
+		{
+			name:     "ParseTemplate_EmptyTemplate_ParsingSucceeded",
+			template: "",
+			args:     nil,
+			want:     []byte(""),
+			wantErr:  false,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := ParseTemplate(test.template, test.args)
+			if err == nil && test.wantErr {
+				t.Errorf("expected an error, but got none")
+			}
+			if err != nil && !test.wantErr {
+				t.Errorf("unexpected error, got: %v", err)
+			}
+			if err != nil && test.wantErr && !strings.Contains(err.Error(), test.errMsg) {
+				t.Errorf("expected error message %s to be in %s", test.errMsg, err.Error())
+			}
+			if !bytes.Equal(got, test.want) {
+				t.Errorf("expected parsed template bytes to be %v, but got %v", test.want, got)
+			}
+		})
+	}
+}