4 files changed, 60 insertions, 2 deletions
diff --git a/packages/browser/jest-environment.js b/packages/browser/jest-environment.js
new file mode 100644
index 0000000..c3a9135
--- /dev/null
+++ b/packages/browser/jest-environment.js
@@ -0,0 +1,22 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+const Environment = require('jest-environment-jsdom');
+
+/**
+ * Set up a custom JSDOM-based test environment for Jest so we can add things JSDOM doesn't support
+ */
+class CustomTestEnvironment extends Environment {
+  async setup() {
+    await super.setup();
+    /**
+     * JSDOM doesn't implement TextEncoder so we need to fake it with Node's
+     *
+     * Solved thanks to https://stackoverflow.com/a/57713960/2133271
+     */
+    if (typeof this.global.TextEncoder === 'undefined') {
+      const { TextEncoder } = require('util');
+      this.global.TextEncoder = TextEncoder;
+    }
+  }
+}
+
+module.exports = CustomTestEnvironment;
diff --git a/packages/browser/jest.config.js b/packages/browser/jest.config.js
index c934d3f..b9a5083 100644
--- a/packages/browser/jest.config.js
+++ b/packages/browser/jest.config.js
@@ -2,6 +2,6 @@ const rootConfig = require('../../jest.config');
 
 module.exports = {
   ...rootConfig,
-  testEnvironment: 'jsdom',
+  testEnvironment: '<rootDir>/jest-environment.js',
   setupFilesAfterEnv: ['<rootDir>/src/setupTests.ts'],
 };
diff --git a/packages/browser/src/helpers/toUint8Array.ts b/packages/browser/src/helpers/toUint8Array.ts
index ed4aa5d..1855dd7 100644
--- a/packages/browser/src/helpers/toUint8Array.ts
+++ b/packages/browser/src/helpers/toUint8Array.ts
@@ -1,7 +1,9 @@
+const utf8Encoder = new TextEncoder();
+
 /**
  * A helper method to convert an arbitrary string sent from the server to a Uint8Array the
  * authenticator will expect.
  */
 export default function toUint8Array(value: string): Uint8Array {
-  return Uint8Array.from(value, c => c.charCodeAt(0));
+  return utf8Encoder.encode(value);
 }
diff --git a/packages/browser/src/methods/startAssertion.test.ts b/packages/browser/src/methods/startAssertion.test.ts
index 669e8eb..e919d18 100644
--- a/packages/browser/src/methods/startAssertion.test.ts
+++ b/packages/browser/src/methods/startAssertion.test.ts
@@ -17,6 +17,7 @@ const mockClientDataJSON = 'mockClientDataJSON';
 const mockSignature = 'mockSignature';
 const mockUserHandle = 'mockUserHandle';
 
+// With ASCII challenge
 const goodOpts1: PublicKeyCredentialRequestOptionsJSON = {
   challenge: 'fizz',
   allowCredentials: [
@@ -29,6 +30,13 @@ const goodOpts1: PublicKeyCredentialRequestOptionsJSON = {
   timeout: 1,
 };
 
+// With UTF-8 challenge
+const goodOpts2UTF8: PublicKeyCredentialRequestOptionsJSON = {
+  challenge: 'やれやれだぜ',
+  allowCredentials: [],
+  timeout: 1,
+};
+
 beforeEach(() => {
   mockNavigatorGet.mockReset();
   mockSupportsWebauthn.mockReset();
@@ -120,3 +128,29 @@ test('should throw error if assertion is cancelled for some reason', async done
 
   done();
 });
+
+test('should handle UTF-8 challenges', async done => {
+  mockSupportsWebauthn.mockReturnValue(true);
+
+  // Stub out a response so the method won't throw
+  mockNavigatorGet.mockImplementation(
+    (): Promise<any> => {
+      return new Promise(resolve => {
+        resolve({
+          response: {},
+          getClientExtensionResults: () => ({}),
+        });
+      });
+    },
+  );
+
+  await startAssertion(goodOpts2UTF8);
+
+  const argsPublicKey = mockNavigatorGet.mock.calls[0][0].publicKey;
+
+  expect(JSON.stringify(argsPublicKey.challenge)).toEqual(
+    '{"0":227,"1":130,"2":132,"3":227,"4":130,"5":140,"6":227,"7":130,"8":132,"9":227,"10":130,"11":140,"12":227,"13":129,"14":160,"15":227,"16":129,"17":156}',
+  );
+
+  done();
+});