Add a test helper for fixing random seeds

Author: szymonlopaciuk

xobjects/test_helpers.py

@@ -83,3 +83,19 @@ def requires_context(context_name: str):
         return lambda test_function: test_function
 
     return pytest.mark.skip(f"{context_name} is unavailable on this platform.")
+
+
+def fix_random_seed(seed: int):
+    """Decorator to fix the random seed for a test."""
+    def decorator(test_function):
+        @wraps(test_function)
+        def wrapper(*args, **kwargs):
+            import numpy as np
+            rng_state = np.random.get_state()
+            try:
+                np.random.seed(seed)
+                test_function(*args, **kwargs)
+            finally:
+                np.random.set_state(rng_state)
+        return wrapper
+    return decorator