switch to an id, fix test

Author: physik932

spec/app.spec.js

@@ -45,7 +45,7 @@ describe('App Initialization', () => {
 
     it('should display an error when no templates are input', () => {
       expect(errorSpy).toBeCalled()
-      expect(document.querySelector('.error')).not.toBe(null)
+      expect(document.querySelector('#error-card')).not.toBe(null)
     })
   })
 

src/templates/error.js

@@ -3,7 +3,7 @@
  */
 export default function (error) {
   return (`
-    <div class="card text-center">
+    <div id="error-card" class="card text-center">
       <div class="card-body">
         <div class="alert alert-danger" role="alert">
           ${error}