test CLI parsing gpus (#2284)

* cli gpus

* test

* test

tests/models/test_gpu.py

@@ -171,7 +171,7 @@ def test_root_gpu_property_0_passing(mocked_device_count_0, gpus, expected_root_
 ])
 def test_root_gpu_property_0_raising(mocked_device_count_0, gpus, expected_root_gpu, distributed_backend):
     with pytest.raises(MisconfigurationException):
-        Trainer(gpus=gpus, distributed_backend=distributed_backend).root_gpu
+        Trainer(gpus=gpus, distributed_backend=distributed_backend)
 
 
 @pytest.mark.gpus_param_tests

tests/trainer/test_trainer_cli.py

@@ -5,6 +5,7 @@ from argparse import ArgumentParser, Namespace
 from unittest import mock
 
 import pytest
+import torch
 
 import tests.base.utils as tutils
 from pytorch_lightning import Trainer
@@ -91,7 +92,6 @@ def test_add_argparse_args_redefined_error(cli_args, monkeypatch):
         parser.parse_args(cli_args)
 
 
-# todo: add also testing for "gpus"
 @pytest.mark.parametrize(['cli_args', 'expected'], [
     pytest.param('--auto_lr_find --auto_scale_batch_size power',
                  {'auto_lr_find': True, 'auto_scale_batch_size': 'power', 'early_stop_callback': False}),
@@ -113,10 +113,25 @@ def test_argparse_args_parsing(cli_args, expected):
     assert Trainer.from_argparse_args(args)
 
 
-@pytest.mark.skipif(
-    sys.version_info < (3, 7),
-    reason="signature inspection while mocking is not working in Python < 3.7 despite autospec"
-)
+@pytest.mark.parametrize(['cli_args', 'expected_gpu'], [
+    pytest.param('--gpus 1', [0]),
+    pytest.param('--gpus 0,', [0]),
+])
+@pytest.mark.skipif(not torch.cuda.is_available(), reason="test requires GPU machine")
+def test_argparse_args_parsing_gpus(cli_args, expected_gpu):
+    """Test multi type argument with bool."""
+    cli_args = cli_args.split(' ') if cli_args else []
+    with mock.patch("argparse._sys.argv", ["any.py"] + cli_args):
+        parser = ArgumentParser(add_help=False)
+        parser = Trainer.add_argparse_args(parent_parser=parser)
+        args = Trainer.parse_argparser(parser)
+
+    trainer = Trainer.from_argparse_args(args)
+    assert trainer.data_parallel_device_ids == expected_gpu
+
+
+@pytest.mark.skipif(sys.version_info < (3, 7),
+                    reason="signature inspection while mocking is not working in Python < 3.7 despite autospec")
 @pytest.mark.parametrize(['cli_args', 'extra_args'], [
     pytest.param({}, {}),
     pytest.param({'logger': False}, {}),