Testing and types updates (#39657)

app/javascript/mastodon/utils/objects.test.ts

@@ -2,13 +2,13 @@
 import { getNestedProperty } from './objects';
 
 describe('getNestedProperty', () => {
+  const obj = { a: { b: { c: 42 } } } as const;
+
   test('returns the value of a nested property if it exists', () => {
-    const obj = { a: { b: { c: 42 } } };
     expect(getNestedProperty(obj, 'a', 'b', 'c')).toBe(42);
   });
 
   test('returns undefined if any part of the path does not exist', () => {
-    const obj = { a: { b: { c: 42 } } };
     expect(getNestedProperty(obj, 'a', 'x', 'c')).toBeUndefined();
     expect(getNestedProperty(obj, 'a', 'b', 'x')).toBeUndefined();
     expect(getNestedProperty(obj, 'x', 'b', 'c')).toBeUndefined();
@@ -20,8 +20,7 @@ describe('getNestedProperty', () => {
     expect(getNestedProperty('string', 'a', 'b')).toBeUndefined();
   });
 
-  test('returns undefined if no keys are provided', () => {
-    const obj = { a: 1 };
-    expect(getNestedProperty(obj)).toBeUndefined();
+  test('returns the object if no keys are provided', () => {
+    expect(getNestedProperty({ a: 1 })).toStrictEqual({ a: 1 });
   });
 });