refactor: improve code cov

Author: mdjastrzebski

src/character-classes/__tests__/any-of.test.ts

@@ -3,6 +3,7 @@ import { oneOrMore } from '../../quantifiers/base';
 import { anyOf } from '../any-of';
 
 test('"anyOf" base cases', () => {
+  expect(p(anyOf(''))).toBe('');
   expect(p(anyOf('a'))).toBe('a');
   expect(p(anyOf('abc'))).toBe('[abc]');
 });

src/character-classes/compiler.ts

@@ -6,7 +6,7 @@ export function compileCharacterClass({ characters }: CharacterClass): string {
   }
 
   if (characters.length === 1) {
-    return characters[0] ?? '';
+    return characters[0]!;
   }
 
   return `[${escapeHypen(characters).join('')}]`;