imageFilenames and imageFilename, backend integration tests, frontend tests, removed username references

frontend/jest.env.js

@@ -0,0 +1,25 @@
+const JSDOMEnvironment = require('jest-environment-jsdom').default;
+const { TextEncoder, TextDecoder } = require('util');
+
+class CustomEnvironment extends JSDOMEnvironment {
+  constructor(config, context) {
+    super(config, context);
+
+    // Add polyfills to global before any test code runs
+    this.global.TextEncoder = TextEncoder;
+    this.global.TextDecoder = TextDecoder;
+
+    // BroadcastChannel polyfill
+    this.global.BroadcastChannel = class BroadcastChannel {
+      constructor(name) {
+        this.name = name;
+      }
+      postMessage() {}
+      close() {}
+      addEventListener() {}
+      removeEventListener() {}
+    };
+  }
+}
+
+module.exports = CustomEnvironment;