diff --git a/refactron/verification/checks/test_gate.py b/refactron/verification/checks/test_gate.py
index 3f8327f..cd6ca20 100644
--- a/refactron/verification/checks/test_gate.py
+++ b/refactron/verification/checks/test_gate.py
@@ -1,3 +1,61 @@
+import ast
+from pathlib import Path
+from typing import Dict, List, Optional
+
+# Global cache for module -> relevant tests mapping
+# Structure: {project_root_str: {target_module: [test_paths]}}
+_TEST_DISCOVERY_CACHE: Dict[str, Dict[str, List[Path]]] = {}
+
+
+class TestSuiteGate:
+    def __init__(self, search_root: Path, project_root: Optional[Path] = None):
+        self.search_root = search_root
+        self.project_root = project_root
+
+    def _imports_module(self, test_file: Path, target_module: str) -> bool:
+        try:
+            source_code = test_file.read_text(encoding="utf-8")
+            tree = ast.parse(source_code)
+            
+            for node in ast.walk(tree):
+                if isinstance(node, ast.Import):
+                    for alias in node.names:
+                        if target_module in alias.name:
+                            return True
+                elif isinstance(node, ast.ImportFrom):
+                    if node.module and target_module in node.module:
+                        return True
+        except Exception:
+            pass
+        return False
+
+    def _find_relevant_tests(self, target_module: str) -> List[Path]:
+        cache_key = str(self.project_root.resolve()) if self.project_root else str(self.search_root.resolve())
+        
+        # Check cache
+        if cache_key in _TEST_DISCOVERY_CACHE and target_module in _TEST_DISCOVERY_CACHE[cache_key]:
+            return _TEST_DISCOVERY_CACHE[cache_key][target_module]
+            
+        relevant_tests = []
+        ignore_patterns = {"venv", ".venv", "site-packages", "node_modules", ".git", ".tox", ".pytest_cache", "__pycache__"}
+        
+        for p in self.search_root.rglob("*.py"):
+            # Skip obvious non-target paths if project_root is set
+            if self.project_root:
+                # Check if any parent directory is in the ignore list
+                if any(part in ignore_patterns for part in p.parts):
+                    continue
+                    
+            if p.is_file() and p.name.startswith("test_"):
+                if self._imports_module(p, target_module):
+                    relevant_tests.append(p)
+                    
+        # Update cache
+        if cache_key not in _TEST_DISCOVERY_CACHE:
+            _TEST_DISCOVERY_CACHE[cache_key] = {}
+            
+        _TEST_DISCOVERY_CACHE[cache_key][target_module] = relevant_tests
+        return relevant_tests
 """TestSuiteGate — Check 3: run relevant tests against transformed code."""
 
 import ast