feat: add test_mode module for shared test mode utilities

autoconf/__init__.py

@@ -9,6 +9,7 @@
 from .json_prior.config import JSONPriorConfig
 
 from .setup_colab import for_autolens
+from .test_mode import test_mode_level, is_test_mode
 
 
 __version__ = "2026.4.5.3"

autoconf/test_mode.py

@@ -0,0 +1,20 @@
+import os
+
+
+def test_mode_level():
+    """
+    Return the current test mode level.
+
+    0 = off (normal operation)
+    1 = reduce sampler iterations to minimum (existing behavior)
+    2 = bypass sampler entirely, call likelihood once
+    3 = bypass sampler entirely, skip likelihood call
+    """
+    return int(os.environ.get("PYAUTOFIT_TEST_MODE", "0"))
+
+
+def is_test_mode():
+    """
+    Return True if any test mode is active.
+    """
+    return test_mode_level() > 0