diff --git a/src/rz/angular/ast-to-html/ast-to-html.ts b/src/rz/angular/ast-to-html/ast-to-html.ts
index ef1d30e..ba7d082 100644
--- a/src/rz/angular/ast-to-html/ast-to-html.ts
+++ b/src/rz/angular/ast-to-html/ast-to-html.ts
@@ -9,7 +9,7 @@
 //     Text,
 //   } from "angular-html-parser/lib/compiler/src/ml_parser/ast";
 
-export function astToHtml(rootNodes: any): string {
+export function astToHtml(rootNodes: any): any {
   return rootNodes.map(nodeToString).join("");
 }
   
@@ -27,9 +27,11 @@ export function astToHtml(rootNodes: any): string {
         return docTypeToString(node);
       case "comment":
         return commentToString(node);
+      default:  
+        return ''
     }
   }
-  function elementToString(node: any): string {
+  function elementToString(node: any): any {
     return `<${node.name}${astToHtml(node.attrs)}>${astToHtml(node.children)}</${
       node.name
     }>`;
diff --git a/tsconfig.spec.json b/tsconfig.spec.json
new file mode 100644
index 0000000..958dfb3
--- /dev/null
+++ b/tsconfig.spec.json
@@ -0,0 +1,10 @@
+{
+    "extends": "./tsconfig.base.json",
+    "compilerOptions": {
+      "outDir": "../../dist/out-tsc",
+      "module": "commonjs",
+      "types": ["jest", "node"]
+    },
+    "include": ["**/*.spec.ts", "**/*.d.ts", "jest.config.ts"]
+  }
+  
\ No newline at end of file