Introduce check_sobol_node test helper (#4729)

Summary:

Simplifies common checks for num initialization trials etc that we do for node based GS

Differential Revision:
D89932177

Privacy Context Container: L1307644

Author: saitcakmak

ax/utils/testing/modeling_stubs.py

@@ -6,6 +6,7 @@
 
 # pyre-strict
 
+import unittest
 from logging import Logger
 from typing import Any
 
@@ -62,6 +63,7 @@
 from botorch.models.transforms.input import InputTransform, Normalize
 from botorch.models.transforms.outcome import OutcomeTransform, Standardize
 from gpytorch.mlls.exact_marginal_log_likelihood import ExactMarginalLogLikelihood
+from pyre_extensions import assert_is_instance
 
 logger: Logger = get_logger(__name__)
 
@@ -337,6 +339,38 @@ def sobol_gpei_generation_node_gs(
     return sobol_mbm_GS_nodes
 
 
+def check_sobol_node(
+    test_case: unittest.TestCase,
+    gs: GenerationStrategy,
+    expected_num_trials: int,
+    expected_min_trials_observed: int | None = None,
+) -> None:
+    """Helper to check common Sobol node properties.
+
+    Args:
+        test_case: The test case instance for assertions.
+        gs: The generation strategy to check.
+        expected_num_trials: The expected number of trials (threshold).
+        expected_min_trials_observed: The expected min_trials_observed threshold.
+            If None, the check is skipped.
+    """
+    sobol_node = gs._nodes[0]
+    test_case.assertEqual(
+        sobol_node.generator_specs[0].generator_enum, Generators.SOBOL
+    )
+    # First MinTrials criterion has the num_trials threshold.
+    test_case.assertEqual(
+        assert_is_instance(sobol_node.transition_criteria[0], MinTrials).threshold,
+        expected_num_trials,
+    )
+    if expected_min_trials_observed is not None:
+        # Second MinTrials criterion has the min_trials_observed threshold.
+        test_case.assertEqual(
+            assert_is_instance(sobol_node.transition_criteria[1], MinTrials).threshold,
+            expected_min_trials_observed,
+        )
+
+
 def get_sobol_MBM_MTGP_gs() -> GenerationStrategy:
     return GenerationStrategy(
         nodes=[