[Bug][Localhost] fix Json parse issue when trying to load battle-anim (#3455)

* add content-type check for loading battle-anims

* add missing `headers` to response mocks

src/data/battle-anims.ts

@@ -485,7 +485,8 @@ export function initMoveAnim(scene: BattleScene, move: Moves): Promise<void> {
       const fetchAnimAndResolve = (move: Moves) => {
         scene.cachedFetch(`./battle-anims/${moveName}.json`)
           .then(response => {
-            if (!response.ok) {
+            const contentType = response.headers.get("content-type");
+            if (!response.ok || contentType?.indexOf("application/json") === -1) {
               console.error(`Could not load animation file for move '${moveName}'`, response.status, response.statusText);
               populateMoveAnim(move, moveAnims.get(defaultMoveAnim));
               return resolve();

src/test/utils/gameWrapper.ts

@@ -242,6 +242,7 @@ function createFetchResponse(data) {
   return {
     ok: true,
     status: 200,
+    headers: new Headers(),
     json: () => Promise.resolve(data),
     text: () => Promise.resolve(JSON.stringify(data)),
   };
@@ -251,6 +252,7 @@ function createFetchBadResponse(data) {
   return {
     ok: false,
     status: 404,
+    headers: new Headers(),
     json: () => Promise.resolve(data),
     text: () => Promise.resolve(JSON.stringify(data)),
   };

src/test/utils/mocks/mockFetch.ts

@@ -23,10 +23,13 @@ export const MockFetch = (input, init) => {
     }
   }
 
-  return Promise.resolve({
+  const response: Partial<Response> = {
     ok: true,
     status: 200,
     json: responseHandler,
     text: responseText,
-  });
+    headers: new Headers({}),
+  };
+
+  return Promise.resolve(response);
 };