[sonic-pcie] Add UT for pcie_common.py (sonic-net#293)

Description
Add unit testcases for pcie_common.py
Code coverage improved to 86%.

Motivation and Context
To improve code coverage for pcie_common.py

tests/pcie_common_test.py

@@ -0,0 +1,214 @@
+import os
+import sys
+import yaml
+from sonic_platform_base.sonic_pcie.pcie_common import PcieUtil
+
+if sys.version_info.major == 3:
+    from unittest import mock
+    BUILTINS = 'builtins'
+else:
+    import mock
+    BUILTINS = '__builtin__'
+
+tests_dir = os.path.dirname(os.path.abspath(__file__))
+pcie_config_file = os.path.join(tests_dir, 'pcie.yaml')
+
+lspci_output = '''\
+00:01.0 PCI A
+00:02.0 PCI B
+00:02.1 PCI C
+01:00.0 PCI D
+'''
+
+lspci_ID_output = '''\
+00:01.0 0001: 0000:000a
+00:02.0 0002: 0000:000b
+00:02.1 0003: 0000:000c
+01:00.0 0004: 0000:000d
+'''
+
+pci_sysfs_paths = [
+    '/sys/bus/pci/devices/0000:00:01.0',
+    '/sys/bus/pci/devices/0000:00:02.0',
+    '/sys/bus/pci/devices/0000:00:02.1',
+    '/sys/bus/pci/devices/0000:01:00.0'
+]
+
+pcie_device_list = [
+    {'bus': '00', 'dev': '01', 'fn': '0', 'id': '000a', 'name': 'PCI A'},
+    {'bus': '00', 'dev': '02', 'fn': '0', 'id': '000b', 'name': 'PCI B'},
+    {'bus': '00', 'dev': '02', 'fn': '1', 'id': '000c', 'name': 'PCI C'},
+    {'bus': '01', 'dev': '00', 'fn': '0', 'id': '000d', 'name': 'PCI D'},
+]
+
+pcie_check_output = [
+    {'bus': '00', 'dev': '01', 'fn': '0', 'id': '000a', 'name': 'PCI A', 'result': 'Passed'},
+    {'bus': '00', 'dev': '02', 'fn': '0', 'id': '000b', 'name': 'PCI B', 'result': 'Passed'},
+    {'bus': '00', 'dev': '02', 'fn': '1', 'id': '000c', 'name': 'PCI C', 'result': 'Passed'},
+    {'bus': '01', 'dev': '00', 'fn': '0', 'id': '000d', 'name': 'PCI D', 'result': 'Passed'}
+]
+
+pcie_aer_correctable_content = '''\
+RxErr 0
+BadTLP 1
+BadDLLP 2
+Rollover 3
+Timeout 4
+NonFatalErr 5
+CorrIntErr 6
+HeaderOF 7
+TOTAL_ERR_COR 28
+'''
+
+pcie_aer_fatal_content = '''\
+Undefined 0
+DLP 1
+SDES 2
+TLP 3
+FCP 4
+CmpltTO 5
+CmpltAbrt 6
+UnxCmplt 7
+RxOF 8
+MalfTLP 9
+ECRC 0
+UnsupReq 1
+ACSViol 2
+UncorrIntErr 3
+BlockedTLP 4
+AtomicOpBlocked 5
+TLPBlockedErr 6
+TOTAL_ERR_FATAL 66
+'''
+
+pcie_aer_nonfatal_content = '''\
+Undefined 0
+DLP 1
+SDES 2
+TLP 3
+FCP 4
+CmpltTO 5
+CmpltAbrt 6
+UnxCmplt 7
+RxOF 8
+MalfTLP 9
+ECRC 0
+UnsupReq 1
+ACSViol 2
+UncorrIntErr 3
+BlockedTLP 4
+AtomicOpBlocked 5
+TLPBlockedErr 6
+TOTAL_ERR_NONFATAL 66
+'''
+
+pcie_aer_stats = {
+    'correctable': {
+        'RxErr': '0', 'BadTLP': '1', 'BadDLLP': '2', 'Rollover': '3',
+        'Timeout': '4', 'NonFatalErr': '5', 'CorrIntErr': '6', 'HeaderOF': '7',
+        'TOTAL_ERR_COR': '28'
+    },
+    'fatal': {
+        'Undefined': '0', 'DLP': '1', 'SDES': '2', 'TLP': '3', 'FCP': '4',
+        'CmpltTO': '5', 'CmpltAbrt': '6', 'UnxCmplt': '7', 'RxOF': '8',
+        'MalfTLP': '9', 'ECRC': '0', 'UnsupReq': '1', 'ACSViol': '2',
+        'UncorrIntErr': '3', 'BlockedTLP': '4', 'AtomicOpBlocked': '5',
+        'TLPBlockedErr': '6', 'TOTAL_ERR_FATAL': '66'
+    },
+    'non_fatal': {
+        'Undefined': '0', 'DLP': '1', 'SDES': '2', 'TLP': '3', 'FCP': '4',
+        'CmpltTO': '5', 'CmpltAbrt': '6', 'UnxCmplt': '7', 'RxOF': '8',
+        'MalfTLP': '9', 'ECRC': '0', 'UnsupReq': '1', 'ACSViol': '2',
+        'UncorrIntErr': '3', 'BlockedTLP': '4', 'AtomicOpBlocked': '5',
+        'TLPBlockedErr': '6', 'TOTAL_ERR_NONFATAL': '66'
+    },
+}
+
+
+class TestPcieCommon:
+
+    @mock.patch('subprocess.Popen')
+    def test_get_pcie_devices(self, subprocess_popen_mock):
+
+        def subprocess_popen_side_effect(*args, **kwargs):
+            if args[0] == 'sudo lspci':
+                output = lspci_output.splitlines()
+            elif args[0] == 'sudo lspci -n':
+                output = lspci_ID_output.splitlines()
+
+            popen_mock = mock.Mock()
+            popen_attributes = {
+                'returncode': 0,
+                'communicate.return_value': ('', ''),
+                'stdout.readlines.return_value': output
+            }
+            popen_mock.configure_mock(**popen_attributes)
+            return popen_mock
+
+        subprocess_popen_mock.side_effect = subprocess_popen_side_effect
+        pcieutil = PcieUtil(tests_dir)
+        result = pcieutil.get_pcie_device()
+        assert result == pcie_device_list
+
+    @mock.patch('os.path.exists')
+    def test_get_pcie_check(self, os_path_exists_mock):
+
+        def os_path_exists_side_effect(*args):
+            return bool(args[0] in pci_sysfs_paths)
+
+        os_path_exists_mock.side_effect = os_path_exists_side_effect
+        pcieutil = PcieUtil(tests_dir)
+        sample_pcie_config = yaml.dump(pcie_device_list)
+
+        open_mock = mock.mock_open(read_data=sample_pcie_config)
+        with mock.patch('{}.open'.format(BUILTINS), open_mock):
+            result = pcieutil.get_pcie_check()
+            open_mock.assert_called_once_with(pcie_config_file)
+            assert result == pcie_check_output
+
+    @mock.patch('os.path.isfile', mock.MagicMock(return_value=True))
+    @mock.patch('{}.open'.format(BUILTINS))
+    def test_get_pcie_aer_stats(self, open_mock):
+
+        def open_mock_side_effect(*args):
+            file_content = ''
+            if os.path.dirname(args[0]) == pci_sysfs_paths[0]:
+                file_name = os.path.basename(args[0])
+                if file_name == 'aer_dev_correctable':
+                    file_content = pcie_aer_correctable_content
+                elif file_name == 'aer_dev_fatal':
+                    file_content = pcie_aer_fatal_content
+                elif file_name == 'aer_dev_nonfatal':
+                    file_content = pcie_aer_nonfatal_content
+
+            return mock.mock_open(read_data=file_content).return_value
+
+        open_mock.side_effect = open_mock_side_effect
+        pcieutil = PcieUtil(tests_dir)
+        test_device = pcie_device_list[0]
+        result = pcieutil.get_pcie_aer_stats(bus=int(test_device['bus']),
+                                             dev=int(test_device['dev']),
+                                             func=int(test_device['fn']))
+        assert result == pcie_aer_stats
+
+    @mock.patch('sonic_platform_base.sonic_pcie.pcie_common.PcieUtil.get_pcie_device', mock.MagicMock(return_value=pcie_device_list))
+    def test_dump_conf_yaml(self):
+        pcieutil = PcieUtil(tests_dir)
+
+        # Verify pcie config path before writing to file
+        open_mock = mock.mock_open()
+        with mock.patch('{}.open'.format(BUILTINS), open_mock):
+            pcieutil.dump_conf_yaml()
+            open_mock.assert_called_once_with(pcie_config_file, 'w')
+
+        pcieutil.dump_conf_yaml()
+        with open(pcie_config_file) as fd:
+            result = yaml.safe_load(fd)
+
+        assert result == pcie_device_list
+
+    @classmethod
+    def teardown_class(cls):
+        # Cleanup generated config
+        if os.path.isfile(pcie_config_file):
+            os.remove(pcie_config_file)