Arm backend: Seed tests before collection (#20183)

Seed the Arm test RNG during pytest configuration so module-level random
inputs are deterministic before test collection imports model test
modules. Keep the per-test seeding fixture for reproducible test
execution.

This will make tests behave less random and hopefully fix some flakeynes
in testing/CI.

For example test_dl3_arm.py failes about 5% of the time before this fix
due to it getting non seeded random numbers.



cc @digantdesai @freddan80 @per @oscarandersson8218 @mansnils
@Sebastian-Larsson @robell @rascani

Signed-off-by: Zingo Andersen <Zingo.Andersen@arm.com>

Author: zingo

backends/arm/test/conftest.py

@@ -26,6 +26,7 @@ def pytest_configure(config):
         pytest._test_options["llama_inputs"] = config.option.llama_inputs  # type: ignore[attr-defined]
 
     logging.basicConfig(stream=sys.stdout)
+    _set_random_seed()
 
 
 def pytest_collection_modifyitems(config, items):
@@ -78,24 +79,28 @@ def set_random_seed():
         ARM_TEST_SEED=3478246 pytest --config-file=/dev/null --verbose -s --color=yes  backends/arm/test/ops/test_avg_pool.py -k <TESTCASE>
 
     """
+    _set_random_seed()
+
+
+def _set_random_seed():
     import torch
 
     seed_env = os.environ.get("ARM_TEST_SEED", "0")
     if seed_env == "RANDOM":
         random.seed()  # reset seed, in case any other test has fiddled with it
         seed = random.randint(0, 2**32 - 1)  # nosec B311 - non-crypto seed for tests
         torch.manual_seed(seed)
+        print(f" ARM_TEST_SEED=RANDOM using:{seed} ", end=" ")
     elif str.isdigit(seed_env):
         seed = int(seed_env)
         random.seed(seed)
         torch.manual_seed(seed)
+        print(f" ARM_TEST_SEED={seed} ", end=" ")
     else:
         raise TypeError(
             "ARM_TEST_SEED env variable must be integers or the string RANDOM"
         )
 
-    print(f" ARM_TEST_SEED={seed} ", end=" ")
-
 
 # ==== End of Pytest fixtures =====