swap to using textdecoder

src/core.ts

@@ -1185,7 +1185,11 @@ export const toBase64 = (str: string | Uint8Array | null | undefined): string =>
   }
 
   if (typeof btoa !== 'undefined') {
-    return btoa(typeof str === 'string' ? str : String(str));
+    if (typeof str === 'string') {
+      return btoa(str);
+    } else {
+      return btoa(new TextDecoder().decode(str));
+    }
   }
 
   throw new FinchError('Cannot generate b64 string; Expected `Buffer` or `btoa` to be defined');

tests/core.test.ts

@@ -0,0 +1,43 @@
+import { toBase64 } from '@tryfinch/finch-api/core';
+
+describe('toBase64', () => {
+  const testCases = [
+    {
+      input: 'hello world',
+      expected: 'aGVsbG8gd29ybGQ=',
+    },
+    {
+      input: new Uint8Array([104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100]),
+      expected: 'aGVsbG8gd29ybGQ=',
+    },
+    {
+      input: undefined,
+      expected: '',
+    },
+  ];
+  describe('with Buffer', () => {
+    test('it converts to base64', async () => {
+      testCases.forEach(({ input, expected }) => {
+        expect(toBase64(input)).toBe(expected);
+      });
+    });
+  });
+
+  describe('without buffer', () => {
+    let originalBuffer: BufferConstructor;
+    beforeAll(() => {
+      originalBuffer = globalThis.Buffer;
+      // @ts-expect-error Can't assign undefined to BufferConstructor
+      globalThis.Buffer = undefined;
+    });
+    afterAll(() => {
+      globalThis.Buffer = originalBuffer;
+    });
+
+    test('it converts to base64', async () => {
+      testCases.forEach(({ input, expected }) => {
+        expect(toBase64(input)).toBe(expected);
+      });
+    });
+  });
+});