[UnitTests] Expose TVM pytest helpers as plugin

Previously, pytest helper utilities such as automatic parametrization
of `target`/`dev`, or `tvm.testing.parameter` were only available for
tests within the `${TVM_HOME}/tests` directory.  This PR extracts the
helper utilities into an importable plugin, which can be used in
external tests (e.g. one-off debugging).

conftest.py

@@ -14,36 +14,5 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-import pytest
-from pytest import ExitCode
 
-import tvm
-import tvm.testing
-
-
-def pytest_configure(config):
-    print("enabled targets:", "; ".join(map(lambda x: x[0], tvm.testing.enabled_targets())))
-    print("pytest marker:", config.option.markexpr)
-
-
-@pytest.fixture
-def dev(target):
-    return tvm.device(target)
-
-
-def pytest_generate_tests(metafunc):
-    tvm.testing._auto_parametrize_target(metafunc)
-    tvm.testing._parametrize_correlated_parameters(metafunc)
-
-
-def pytest_collection_modifyitems(config, items):
-    tvm.testing._count_num_fixture_uses(items)
-    tvm.testing._remove_global_fixture_definitions(items)
-
-
-def pytest_sessionfinish(session, exitstatus):
-    # Don't exit with an error if we select a subset of tests that doesn't
-    # include anything
-    if session.config.option.markexpr != "":
-        if exitstatus == ExitCode.NO_TESTS_COLLECTED:
-            session.exitstatus = ExitCode.OK
+pytest_plugins = ["tvm.testing.plugin"]

pytest.ini → python/tvm/testing/__init__.py

@@ -14,13 +14,6 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-[pytest]
-markers =
-    gpu: mark a test as requiring a gpu
-    tensorcore: mark a test as requiring a tensorcore
-    cuda: mark a test as requiring cuda
-    opencl: mark a test as requiring opencl
-    rocm: mark a test as requiring rocm
-    vulkan: mark a test as requiring vulkan
-    metal: mark a test as requiring metal
-    llvm: mark a test as requiring llvm
+"""Namespace for tvm testing utilities"""
+
+from .testing import *

python/tvm/testing/plugin.py

@@ -0,0 +1,82 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""Pytest plugin for using tvm testing extensions.
+
+TVM provides utilities for testing across all supported targets, and
+to more easily parametrize across many inputs.  For more information
+on usage of these features, see documentation in the tvm.testing
+module.
+
+These are enabled by default in all pytests provided by tvm, but may
+be useful externally for one-off testing.  To enable, add the
+following line to the test script, or to the conftest.py in the same
+directory as the test scripts.
+
+     pytest_plugins = ['tvm.testing.plugin']
+
+"""
+
+import pytest
+
+import tvm.testing.testing
+
+
+def pytest_configure(config):
+    """Runs at pytest configure time, defines marks to be used later."""
+    markers = {
+        "gpu": "mark a test as requiring a gpu",
+        "tensorcore": "mark a test as requiring a tensorcore",
+        "cuda": "mark a test as requiring cuda",
+        "opencl": "mark a test as requiring opencl",
+        "rocm": "mark a test as requiring rocm",
+        "vulkan": "mark a test as requiring vulkan",
+        "metal": "mark a test as requiring metal",
+        "llvm": "mark a test as requiring llvm",
+    }
+    for markername, desc in markers.items():
+        config.addinivalue_line("markers", "{}: {}".format(markername, desc))
+
+    print("enabled targets:", "; ".join(map(lambda x: x[0], tvm.testing.enabled_targets())))
+    print("pytest marker:", config.option.markexpr)
+
+
+def pytest_generate_tests(metafunc):
+    """Called once per unit test, modifies/parametrizes it as needed."""
+    tvm.testing.testing._auto_parametrize_target(metafunc)
+    tvm.testing.testing._parametrize_correlated_parameters(metafunc)
+
+
+def pytest_collection_modifyitems(config, items):
+    """Called after all tests are chosen, currently used for bookkeeping."""
+    # pylint: disable=unused-argument
+    tvm.testing.testing._count_num_fixture_uses(items)
+    tvm.testing.testing._remove_global_fixture_definitions(items)
+
+
+@pytest.fixture
+def dev(target):
+    """Give access to the device to tests that need it."""
+    return tvm.device(target)
+
+
+def pytest_sessionfinish(session, exitstatus):
+    # Don't exit with an error if we select a subset of tests that doesn't
+    # include anything
+    if session.config.option.markexpr != "":
+        if exitstatus == pytest.ExitCode.NO_TESTS_COLLECTED:
+            session.exitstatus = pytest.ExitCode.OK