simplified finding duplicates

tests/unit/domain/Script.spec.ts

@@ -0,0 +1,17 @@
+import 'mocha';
+import { expect } from 'chai';
+import { Script } from '@/domain/Script';
+
+describe('Script', () => {
+
+    it('cannot construct with duplicate lines', async () => {
+        // arrange
+        const code = 'duplicate\nduplicate\ntest\nduplicate';
+
+        // act
+        function construct() { return new Script('ScriptName', code, []); }
+
+        // assert
+        expect(construct).to.throw();
+    });
+});