Tests: adds unit tests for pkg/graph/variable.go (#404)

* pkg/graph/variable: adds unit tests for variable package

Author: Rudra-Sankha-Sinhamahapatra

Diff for: pkg/graph/variable/variable_test.go

@@ -0,0 +1,72 @@
+// Copyright 2025 The Kube Resource Orchestrator Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"). You may
+// not use this file except in compliance with the License. A copy of the
+// License is located at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// or in the "license" file accompanying this file. This file 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 variable
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestResourceFieldAddDependencies(t *testing.T) {
+	tests := []struct {
+		name              string
+		initialDeps       []string
+		depsToAdd         []string
+		expectedFinalDeps []string
+	}{
+		{
+			name:              "add new dependencies",
+			initialDeps:       []string{"resource1", "resource2"},
+			depsToAdd:         []string{"resource3", "resource4"},
+			expectedFinalDeps: []string{"resource1", "resource2", "resource3", "resource4"},
+		},
+		{
+			name:              "add duplicate dependencies",
+			initialDeps:       []string{"resource1", "resource2"},
+			depsToAdd:         []string{"resource2", "resource3"},
+			expectedFinalDeps: []string{"resource1", "resource2", "resource3"},
+		},
+		{
+			name:              "add to empty dependencies",
+			initialDeps:       []string{},
+			depsToAdd:         []string{"resource1", "resource2"},
+			expectedFinalDeps: []string{"resource1", "resource2"},
+		},
+		{
+			name:              "add empty dependencies",
+			initialDeps:       []string{"resource1", "resource2"},
+			depsToAdd:         []string{},
+			expectedFinalDeps: []string{"resource1", "resource2"},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			rf := ResourceField{
+				Dependencies: tc.initialDeps,
+			}
+
+			rf.AddDependencies(tc.depsToAdd...)
+
+			assert.ElementsMatch(t, tc.expectedFinalDeps, rf.Dependencies)
+
+			seen := make(map[string]bool)
+			for _, dep := range rf.Dependencies {
+				assert.False(t, seen[dep], "Duplicate dependency found: %s", dep)
+				seen[dep] = true
+			}
+		})
+	}
+}