test: use absolute and complex paths to test normalization

Previous tests were too simple. Now testing paths that would
actually expose concatenation bugs without normalization:

1. Absolute paths (like Windows C:\path issue)
2. Paths with parent directory (..) that need cleaning
3. Paths with redundant separators (//) that need normalization

These tests verify the fix prevents path duplication like:
  /path/test/path/test/file (without normalization)
  /path/test/file (with proper normalization)

Addresses review feedback on PR #5674.

Signed-off-by: Sibasis Padhi <[email protected]>

Author: sibasispadhi

cmd/flux/build_kustomization_test.go

@@ -219,25 +219,37 @@ spec:
 	}
 }
 
-// TestBuildKustomizationWithRelativePaths verifies that relative and absolute
-// paths are handled correctly to prevent path concatenation issues.
-// See: https://github.com/fluxcd/flux2/issues/5673
-func TestBuildKustomizationWithRelativePaths(t *testing.T) {
+// TestBuildKustomizationPathNormalization verifies that absolute and complex
+// paths are normalized to prevent path concatenation bugs (issue #5673).
+// Without normalization, paths could be duplicated like: /path/test/path/test/file
+func TestBuildKustomizationPathNormalization(t *testing.T) {
+	// Get absolute path to testdata to test absolute path handling
+	absTestDataPath, err := filepath.Abs("testdata/build-kustomization/podinfo")
+	if err != nil {
+		t.Fatalf("failed to get absolute path: %v", err)
+	}
+
 	tests := []struct {
 		name       string
 		args       string
 		resultFile string
 		assertFunc string
 	}{
 		{
-			name:       "build with relative path",
-			args:       "build kustomization podinfo --path testdata/build-kustomization/podinfo",
+			name:       "build with absolute path",
+			args:       "build kustomization podinfo --path " + absTestDataPath,
 			resultFile: "./testdata/build-kustomization/podinfo-result.yaml",
 			assertFunc: "assertGoldenTemplateFile",
 		},
 		{
-			name:       "build with dot-slash relative path",
-			args:       "build kustomization podinfo --path ./testdata/build-kustomization/podinfo",
+			name:       "build with complex relative path (parent dir)",
+			args:       "build kustomization podinfo --path ./testdata/build-kustomization/../build-kustomization/podinfo",
+			resultFile: "./testdata/build-kustomization/podinfo-result.yaml",
+			assertFunc: "assertGoldenTemplateFile",
+		},
+		{
+			name:       "build with path containing redundant separators",
+			args:       "build kustomization podinfo --path ./testdata//build-kustomization//podinfo",
 			resultFile: "./testdata/build-kustomization/podinfo-result.yaml",
 			assertFunc: "assertGoldenTemplateFile",
 		},