twister: pytest: Parametrize scope of the dut fixture

Added pytest_dut_scope keyword under harness_config section.
New keyword is used to determine the scope of dut and shell
fixtures in pytest-twister-harness plugin.

Signed-off-by: Grzegorz Chwierut <grzegorz.chwierut@nordicsemi.no>

doc/develop/test/pytest.rst

@@ -69,6 +69,9 @@ DUT (initialize logging, flash device, connect serial etc).
 This fixture yields a device prepared according to the requested type
 (native posix, qemu, hardware, etc.). All types of devices share the same API.
 This allows for writing tests which are device-type-agnostic.
+Scope of this fixture is determined by the ``pytest_dut_scope``
+keyword placed under ``harness_config`` section.
+
 
 .. code-block:: python
 
@@ -81,8 +84,10 @@ shell
 -----
 
 Provide an object with methods used to interact with shell application.
-It calls `wait_for_promt` method, to not start scenario until DUT is ready.
+It calls ``wait_for_promt`` method, to not start scenario until DUT is ready.
-Note that it uses `dut` fixture, so `dut` can be skipped when `shell` is used.
+Note that it uses ``dut`` fixture, so ``dut`` can be skipped when ``shell`` is used.
+Scope of this fixture is determined by the ``pytest_dut_scope``
+keyword placed under ``harness_config`` section.
 
 .. code-block:: python
 

doc/develop/test/twister.rst

@@ -514,6 +514,11 @@ harness_config: <harness configuration options>
     pytest_args: <list of arguments> (default empty)
         Specify a list of additional arguments to pass to ``pytest``.
 
+    pytest_dut_scope: <function|class|module|package|session> (default function)
+        The scope for which ``dut`` and ``shell`` pytest fixtures are shared.
+        If the scope is set to ``function``, DUT is launched for every test case
+        in python script. For ``session`` scope, DUT is launched only once.
+
     robot_test_path: <robot file path> (default empty)
         Specify a path to a file containing a Robot Framework test suite to be run.
 

scripts/pylib/pytest-twister-harness/src/twister_harness/fixtures.py

@@ -36,11 +36,16 @@ def device_object(twister_harness_config: TwisterHarnessConfig) -> Generator[Dev
         device_object.close()
 
 
-@pytest.fixture(scope='function')
+def determine_scope(fixture_name, config):
+    if dut_scope := config.getoption("--dut-scope", None):
+        return dut_scope
+    return 'function'
+
+
+@pytest.fixture(scope=determine_scope)
 def dut(request: pytest.FixtureRequest, device_object: DeviceAdapter) -> Generator[DeviceAdapter, None, None]:
     """Return launched device - with run application."""
-    test_name = request.node.name
+    device_object.initialize_log_files(request.node.name)
-    device_object.initialize_log_files(test_name)
     try:
         device_object.launch()
         yield device_object
@@ -48,7 +53,7 @@ def dut(request: pytest.FixtureRequest, device_object: DeviceAdapter) -> Generat
         device_object.close()
 
 
-@pytest.fixture(scope='function')
+@pytest.fixture(scope=determine_scope)
 def shell(dut: DeviceAdapter) -> Shell:
     """Return ready to use shell interface"""
     shell = Shell(dut, timeout=20.0)

scripts/pylib/pytest-twister-harness/src/twister_harness/plugin.py

@@ -100,6 +100,11 @@ def pytest_addoption(parser: pytest.Parser):
         metavar='PATH',
         help='Script executed after closing serial connection.'
     )
+    twister_harness_group.addoption(
+        '--dut-scope',
+        choices=('function', 'class', 'module', 'package', 'session'),
+        help='The scope for which `dut` and `shell` fixtures are shared.'
+    )
 
 
 def pytest_configure(config: pytest.Config):

scripts/pylib/twister/twisterlib/harness.py

@@ -268,6 +268,7 @@ class Pytest(Harness):
         config = self.instance.testsuite.harness_config
         pytest_root = config.get('pytest_root', ['pytest']) if config else ['pytest']
         pytest_args = config.get('pytest_args', []) if config else []
+        pytest_dut_scope = config.get('pytest_dut_scope', None) if config else None
         command = [
             'pytest',
             '--twister-harness',
@@ -281,6 +282,8 @@ class Pytest(Harness):
         command.extend([os.path.normpath(os.path.join(
             self.source_dir, os.path.expanduser(os.path.expandvars(src)))) for src in pytest_root])
         command.extend(pytest_args)
+        if pytest_dut_scope:
+            command.append(f'--dut-scope={pytest_dut_scope}')
 
         handler: Handler = self.instance.handler
 
@@ -427,7 +430,7 @@ class Pytest(Harness):
             self.instance.execution_time = float(elem_ts.get('time'))
 
             for elem_tc in elem_ts.findall('testcase'):
-                tc = self.instance.get_case_or_create(f"{self.id}.{elem_tc.get('name')}")
+                tc = self.instance.add_testcase(f"{self.id}.{elem_tc.get('name')}")
                 tc.duration = float(elem_tc.get('time'))
                 elem = elem_tc.find('*')
                 if elem is None:

scripts/schemas/twister/testsuite-schema.yaml

@@ -104,6 +104,10 @@ mapping:
             required: false
             sequence:
               - type: str
+          "pytest_dut_scope":
+            type: str
+            enum: ["function", "class", "module", "package", "session"]
+            required: false
           "regex":
             type: seq
             required: false
@@ -304,6 +308,10 @@ mapping:
                 required: false
                 sequence:
                   - type: str
+              "pytest_dut_scope":
+                type: str
+                enum: ["function", "class", "module", "package", "session"]
+                required: false
               "regex":
                 type: seq
                 required: false

scripts/tests/twister/pytest_integration/test_harness_pytest.py

@@ -48,6 +48,25 @@ def test_pytest_command(testinstance: TestInstance, device_type):
         assert c in command
 
 
+def test_pytest_command_dut_scope(testinstance: TestInstance):
+    pytest_harness = Pytest()
+    dut_scope = 'session'
+    testinstance.testsuite.harness_config['pytest_dut_scope'] = dut_scope
+    pytest_harness.configure(testinstance)
+    command = pytest_harness.generate_command()
+    assert f'--dut-scope={dut_scope}' in command
+
+
+def test_pytest_command_extra_args(testinstance: TestInstance):
+    pytest_harness = Pytest()
+    pytest_args = ['-k test1', '-m mark1']
+    testinstance.testsuite.harness_config['pytest_args'] = pytest_args
+    pytest_harness.configure(testinstance)
+    command = pytest_harness.generate_command()
+    for c in pytest_args:
+        assert c in command
+
+
 @pytest.mark.parametrize(
     ('pytest_root', 'expected'),
     [