Untuck tests out of __tests__ directories, colocate with program files

src/utils/comparators.test.ts

@@ -0,0 +1,7 @@
+import { compareId } from './comparators';
+
+test('compareId', () => {
+  expect(compareId('3', '3')).toBe(0);
+  expect(compareId('10', '1')).toBe(1);
+  expect(compareId('99', '100')).toBe(-1);
+});