feat: implement equals validation

Author: glennmichael123

src/validators/strings.ts

@@ -67,6 +67,15 @@ export class StringValidator extends BaseValidator<string> {
     })
   }
 
+  equals(param: string): this {
+    return this.addRule({
+      name: 'equals',
+      test: (value: string) => value === param,
+      message: 'Must be equal to {param}',
+      params: { param },
+    })
+  }
+
   alphanumeric(): this {
     return this.addRule({
       name: 'alphanumeric',

test/validation.test.ts

@@ -40,6 +40,18 @@ describe('Validation Library', () => {
       expect(validator.test('abc123')).toBe(true)
       expect(validator.test('abc-123')).toBe(false)
     })
+
+    test('equals validation - useful for password confirmation', () => {
+      const password = 'mySecurePassword123'
+      const validator = v.string().equals(password)
+      expect(validator.test(password)).toBe(true)
+      expect(validator.test('differentPassword')).toBe(false)
+
+      // Test with empty strings
+      const emptyValidator = v.string().equals('')
+      expect(emptyValidator.test('')).toBe(true)
+      expect(emptyValidator.test('not-empty')).toBe(false)
+    })
   })
 
   describe('Number Validator', () => {