feat: add unit tests for toLowerCase utility function

tests/format.test.ts

@@ -0,0 +1,20 @@
+import { describe, expect, it } from 'vitest'
+import { toLowerCase } from '../src/format'
+
+describe('toLowerCase', () => {
+  it('should convert camelCase to hyphen-case', () => {
+    expect(toLowerCase('camelCase')).toBe('camel-case')
+  })
+
+  it('should convert PascalCase to hyphen-case', () => {
+    expect(toLowerCase('PascalCase')).toBe('pascal-case')
+  })
+
+  it('should handle strings with spaces', () => {
+    expect(toLowerCase('Hello World')).toBe('hello-world')
+  })
+
+  it('should handle empty strings', () => {
+    expect(toLowerCase('')).toBe('')
+  })
+})