fix: resolve CI linting and type errors

src/promptforge/testing/__init__.py

@@ -1,5 +1,19 @@
-from .ab_test import ABTest, ABTestConfig
-from .metrics import TestMetrics, MetricsCollector
-from .results import TestResult, ComparisonResult
+"""A/B testing and validation modules."""
 
-__all__ = ["ABTest", "ABTestConfig", "TestMetrics", "MetricsCollector", "TestResult", "ComparisonResult"]
+from .ab_test import ABTest, ABTestConfig, ABTestResult
+from .validator import Validator, JSONSchemaValidator, RegexValidator, CompositeValidator
+from .metrics import MetricsCollector
+from .results import TestSessionResults, ResultFormatter
+
+__all__ = [
+    "ABTest",
+    "ABTestConfig",
+    "ABTestResult",
+    "Validator",
+    "JSONSchemaValidator",
+    "RegexValidator",
+    "CompositeValidator",
+    "MetricsCollector",
+    "TestSessionResults",
+    "ResultFormatter",
+]