[PATCH 2/5] dts: add random generation seed setting

[Luca Vizzarro <Luca.Vizzarro@arm.com>]

From: Luca Vizzarro <luca.vizzarro@arm.com>

When introducing pseudo-random generation in the test runs we need to
ensure that these can be reproduced by setting a pre-defined seed.
This commits adds the ability to set one or allow for one to be
generated and reported back to the user.

Signed-off-by: Luca Vizzarro <luca.vizzarro@arm.com>
Reviewed-by: Paul Szczpanek <paul.szczepanek@arm.com>
Reviewed-by: Alex Chapman <alex.chapman@arm.com>
---
 doc/guides/tools/dts.rst                   |  5 +++++
 dts/framework/config/__init__.py           |  4 ++++
 dts/framework/config/conf_yaml_schema.json |  4 ++++
 dts/framework/config/types.py              |  2 ++
 dts/framework/runner.py                    |  8 ++++++++
 dts/framework/settings.py                  | 17 +++++++++++++++++
 6 files changed, 40 insertions(+)

diff --git a/doc/guides/tools/dts.rst b/doc/guides/tools/dts.rst
index 515b15e4d8..9b5ea9779c 100644
--- a/doc/guides/tools/dts.rst
+++ b/doc/guides/tools/dts.rst
@@ -251,6 +251,8 @@ DTS is run with ``main.py`` located in the ``dts`` directory after entering Poet
                            ... | DTS_TEST_SUITES='suite, suite case, ...' (default: [])
      --re-run N_TIMES, --re_run N_TIMES
                            [DTS_RERUN] Re-run each test case the specified number of times if a test failure occurs. (default: 0)
+     --random-seed NUMBER  [DTS_RANDOM_SEED] The seed to use with the pseudo-random generator. If not specified, the configuration value is
+                           used instead. If that's also not specified, a random seed is generated. (default: None)
 
 
 The brackets contain the names of environment variables that set the same thing.
@@ -548,6 +550,9 @@ involved in the testing. These can be defined with the following mappings:
    +----------------------------+---------------+---------------------------------------------------+
    | ``traffic_generator_node`` | Node name for the traffic generator node.                         |
    +----------------------------+-------------------------------------------------------------------+
+   | ``random_seed``            | (*optional*) *int* – Allows you to set a seed for pseudo-random   |
+   |                            | generation.                                                       |
+   +----------------------------+-------------------------------------------------------------------+
 
 ``nodes``
    `sequence <https://docs.python.org/3/library/stdtypes.html#sequence-types-list-tuple-range>`_ listing
diff --git a/dts/framework/config/__init__.py b/dts/framework/config/__init__.py
index df60a5030e..269d9ec318 100644
--- a/dts/framework/config/__init__.py
+++ b/dts/framework/config/__init__.py
@@ -445,6 +445,7 @@ class TestRunConfiguration:
         system_under_test_node: The SUT node to use in this test run.
         traffic_generator_node: The TG node to use in this test run.
         vdevs: The names of virtual devices to test.
+        random_seed: The seed to use for pseudo-random generation.
     """
 
     build_targets: list[BuildTargetConfiguration]
@@ -455,6 +456,7 @@ class TestRunConfiguration:
     system_under_test_node: SutNodeConfiguration
     traffic_generator_node: TGNodeConfiguration
     vdevs: list[str]
+    random_seed: int | None
 
     @classmethod
     def from_dict(
@@ -497,6 +499,7 @@ def from_dict(
         vdevs = (
             d["system_under_test_node"]["vdevs"] if "vdevs" in d["system_under_test_node"] else []
         )
+        random_seed = d.get("random_seed", None)
         return cls(
             build_targets=build_targets,
             perf=d["perf"],
@@ -506,6 +509,7 @@ def from_dict(
             system_under_test_node=system_under_test_node,
             traffic_generator_node=traffic_generator_node,
             vdevs=vdevs,
+            random_seed=random_seed,
         )
 
     def copy_and_modify(self, **kwargs) -> Self:
diff --git a/dts/framework/config/conf_yaml_schema.json b/dts/framework/config/conf_yaml_schema.json
index f02a310bb5..df390e8ae2 100644
--- a/dts/framework/config/conf_yaml_schema.json
+++ b/dts/framework/config/conf_yaml_schema.json
@@ -379,6 +379,10 @@
           },
           "traffic_generator_node": {
             "$ref": "#/definitions/node_name"
+          },
+          "random_seed": {
+            "type": "integer",
+            "description": "Optional field. Allows you to set a seed for pseudo-random generation."
           }
         },
         "additionalProperties": false,
diff --git a/dts/framework/config/types.py b/dts/framework/config/types.py
index cf16556403..ce7b784ac8 100644
--- a/dts/framework/config/types.py
+++ b/dts/framework/config/types.py
@@ -121,6 +121,8 @@ class TestRunConfigDict(TypedDict):
     system_under_test_node: TestRunSUTConfigDict
     #:
     traffic_generator_node: str
+    #:
+    random_seed: int
 
 
 class ConfigurationDict(TypedDict):
diff --git a/dts/framework/runner.py b/dts/framework/runner.py
index 6b6f6a05f5..34b1dad5c4 100644
--- a/dts/framework/runner.py
+++ b/dts/framework/runner.py
@@ -20,6 +20,7 @@
 import importlib
 import inspect
 import os
+import random
 import re
 import sys
 from pathlib import Path
@@ -147,6 +148,7 @@ def run(self) -> None:
                 self._logger.info(
                     f"Running test run with SUT '{test_run_config.system_under_test_node.name}'."
                 )
+                self._init_random_seed(test_run_config)
                 test_run_result = self._result.add_test_run(test_run_config)
                 # we don't want to modify the original config, so create a copy
                 test_run_test_suites = list(
@@ -723,3 +725,9 @@ def _exit_dts(self) -> None:
             self._logger.info("DTS execution has ended.")
 
         sys.exit(self._result.get_return_code())
+
+    def _init_random_seed(self, conf: TestRunConfiguration) -> None:
+        """Initialize the random seed to use for the test run."""
+        seed = SETTINGS.random_seed or conf.random_seed or random.randrange(0xFFFF_FFFF)
+        self._logger.info(f"Initializing test run with random seed {seed}")
+        random.seed(seed)
diff --git a/dts/framework/settings.py b/dts/framework/settings.py
index f6303066d4..7744e37f54 100644
--- a/dts/framework/settings.py
+++ b/dts/framework/settings.py
@@ -66,6 +66,12 @@
 
     Re-run each test case this many times in case of a failure.
 
+.. option:: --random-seed
+.. envvar:: DTS_RANDOM_SEED
+
+    The seed to use with the pseudo-random generator. If not specified, the configuration value is
+    used instead. If that's also not specified, a random seed is generated.
+
 The module provides one key module-level variable:
 
 Attributes:
@@ -115,6 +121,8 @@ class Settings:
     test_suites: list[TestSuiteConfig] = field(default_factory=list)
     #:
     re_run: int = 0
+    #:
+    random_seed: int | None = None
 
 
 SETTINGS: Settings = Settings()
@@ -375,6 +383,15 @@ def _get_parser() -> _DTSArgumentParser:
     )
     _add_env_var_to_action(action, "RERUN")
 
+    action = parser.add_argument(
+        "--random-seed",
+        type=int,
+        help="The seed to use with the pseudo-random generator. If not specified, the configuration"
+        " value is used instead. If that's also not specified, a random seed is generated.",
+        metavar="NUMBER",
+    )
+    _add_env_var_to_action(action)
+
     return parser
 
 
-- 
2.34.1