export class EncodingMock implements Xrm.Encoding {
  public xmlAttributeEncode(arg: string): string {
    throw new Error("Not implemented");
  }
  public xmlEncode(arg: string): string {
    throw new Error("Not implemented");
  }

  public htmlAttributeEncode(arg: string): string {
    throw new Error("Not implemented");
  }

  public htmlDecode(arg: string): string {
    throw new Error("Not implemented");
  }

  public htmlEncode(arg: string): string {
    throw new Error("Not implemented");
  }
}

export class EncodingMock implements Xrm.Encoding {
  public xmlAttributeEncode(arg: string): string {
    throw new Error("Not implemented");
  }
  public xmlEncode(arg: string): string {
    throw new Error("Not implemented");
  }
}

--- 
+++ 
@@ -5,4 +5,16 @@
   public xmlEncode(arg: string): string {
     throw new Error("Not implemented");
   }
+
+  public htmlAttributeEncode(arg: string): string {
+    throw new Error("Not implemented");
+  }
+
+  public htmlDecode(arg: string): string {
+    throw new Error("Not implemented");
+  }
+
+  public htmlEncode(arg: string): string {
+    throw new Error("Not implemented");
+  }
 }
Add missing functions in Xrm.Encoding
