[sonic-py-common] Add unit test framework (sonic-net#5238)

**- Why I did it**

To install the framework for adding unit tests to the sonic-py-common package and report coverage.

** How I did it **

- Incorporate pytest and pytest-cov into sonic-py-common package build
- Updgrade version of 'mock' installed to version 3.0.5, the last version which supports Python 2. This fixes a bug where the file object returned from `mock_open()` was not iterable (see https://bugs.python.org/issue32933)
- Add support for Python 3 setuptools and pytest in sonic-slave-buster environment
- Add tests for `device_info.get_machine_info()` and `device_info.get_platform()` functions
- Also add a .gitignore in the root of the sonic-py-common directory, move all related ignores from main .gitignore file, and add ignores for files and dirs generated by pytest-cov

.gitignore

@@ -28,12 +28,6 @@ platform/*/docker-*/Dockerfile
 # Installer-related files and directories
 installer/x86_64/platforms/
 
-src/sonic-py-common/**/*.pyc
-src/sonic-py-common/.eggs/
-src/sonic-py-common/build
-src/sonic-py-common/dist
-src/sonic-py-common/sonic_py_common.egg-info
-
 # Misc. files
 asic_config_checksum
 files/Aboot/boot0

sonic-slave-buster/Dockerfile.j2

@@ -209,8 +209,10 @@ RUN apt-get update && apt-get install -y \
         clang \
         pylint \
         python-pytest \
+        python3-pytest \
         gcovr \
         python-pytest-cov \
+        python3-pytest-cov \
         python-parse \
 # For snmpd
         default-libmysqlclient-dev \
@@ -339,6 +341,21 @@ RUN export VERSION=1.14.2 \
  && echo 'export PATH=$PATH:$GOROOT/bin' >> /etc/bash.bashrc \
  && rm go$VERSION.linux-*.tar.gz
 
+# For building Python packages
+RUN pip install setuptools==40.8.0
+RUN pip3 install setuptools==49.6.00
+
+# For running Python unit tests
+RUN pip install pytest-runner==4.4
+RUN pip3 install pytest-runner==5.2
+RUN pip install mockredispy==2.9.3
+RUN pip3 install mockredispy==2.9.3
+
+# For Python 2 unit tests, we need 'mock'. The last version of 'mock'
+# which supports Python 2 is 3.0.5. In Python 3, 'mock' is part of 'unittest'
+# in the standard library
+RUN pip install mock==3.0.5
+
 # For p4 build
 RUN pip install \
         ctypesgen==1.0.2 \
@@ -357,25 +374,17 @@ RUN apt-get purge -y python-click
 # For sonic utilities testing
 RUN pip install click natsort tabulate netifaces==0.10.7 fastentrypoints
 
-# For sonic snmpagent mock testing
-RUN pip3 install mockredispy==2.9.3
-
 RUN pip3 install "PyYAML>=5.1"
 
 # For sonic-platform-common testing
 RUN pip3 install redis
 
 # For supervisor build
-RUN pip install meld3 mock
+RUN pip install meld3
 
 # For vs image build
 RUN pip install pexpect==4.6.0
 
-# For sonic-utilities build
-RUN pip install mockredispy==2.9.3
-RUN pip install pytest-runner==4.4
-RUN pip install setuptools==40.8.0
-
 # For sonic-swss-common testing
 RUN pip install Pympler==0.8
 

src/sonic-py-common/.gitignore

@@ -0,0 +1,13 @@
+**/*.pyc
+
+# Distribution / packaging 
+*.egg-info/
+.eggs/
+build/
+dist/
+
+# Unit test / coverage reports 
+.cache
+.coverage
+coverage.xml
+htmlcov/

src/sonic-py-common/pytest.ini

@@ -0,0 +1,2 @@
+[pytest]
+addopts = --cov=sonic_py_common --cov-report html --cov-report term --cov-report xml

src/sonic-py-common/setup.cfg

@@ -0,0 +1,2 @@
+[aliases]
+test=pytest

src/sonic-py-common/setup.py

@@ -27,6 +27,13 @@
     packages=[
         'sonic_py_common',
     ],
+    setup_requires= [
+        'pytest-runner'
+    ],
+    tests_require=[
+        'pytest',
+        'mock==3.0.5' # For python 2. Version >=4.0.0 drops support for py2
+    ],
     classifiers=[
         'Intended Audience :: Developers',
         'Operating System :: Linux',
@@ -35,5 +42,6 @@
         'Programming Language :: Python',
     ],
     keywords='SONiC sonic PYTHON python COMMON common',
+    test_suite = 'setup.get_test_suite'
 )
 

src/sonic-py-common/sonic_py_common/device_info.py

@@ -6,7 +6,7 @@
 import yaml
 from natsort import natsorted
 
-# TODD: Replace with swsscommon
+# TODO: Replace with swsscommon
 from swsssdk import ConfigDBConnector, SonicDBConfig
 
 USR_SHARE_SONIC_PATH = "/usr/share/sonic"

src/sonic-py-common/tests/device_info_test.py

@@ -0,0 +1,75 @@
+import os
+import sys
+
+# TODO: Remove this if/else block once we no longer support Python 2
+if sys.version_info.major == 3:
+    from unittest import mock
+else:
+    # Expect the 'mock' package for python 2
+    # https://pypi.python.org/pypi/mock
+    import mock
+
+from sonic_py_common import device_info
+
+
+# TODO: Remove this if/else block once we no longer support Python 2
+if sys.version_info.major == 3:
+    BUILTINS = "builtins"
+else:
+    BUILTINS = "__builtin__"
+
+MACHINE_CONF_CONTENTS = """\
+onie_version=2016.11-5.1.0008-9600
+onie_vendor_id=33049
+onie_machine_rev=0
+onie_arch=x86_64
+onie_config_version=1
+onie_build_date="2017-04-26T11:01+0300"
+onie_partition_type=gpt
+onie_kernel_version=4.10.11
+onie_firmware=auto
+onie_switch_asic=mlnx
+onie_skip_ethmgmt_macs=yes
+onie_machine=mlnx_msn2700
+onie_platform=x86_64-mlnx_msn2700-r0"""
+
+EXPECTED_GET_MACHINE_INFO_RESULT = {
+    'onie_arch': 'x86_64',
+    'onie_skip_ethmgmt_macs': 'yes',
+    'onie_platform': 'x86_64-mlnx_msn2700-r0',
+    'onie_machine_rev': '0',
+    'onie_version': '2016.11-5.1.0008-9600',
+    'onie_machine': 'mlnx_msn2700',
+    'onie_config_version': '1',
+    'onie_partition_type': 'gpt',
+    'onie_build_date': '"2017-04-26T11:01+0300"',
+    'onie_switch_asic': 'mlnx',
+    'onie_vendor_id': '33049',
+    'onie_firmware': 'auto',
+    'onie_kernel_version': '4.10.11'
+}
+
+
+class TestDeviceInfo(object):
+    @classmethod
+    def setup_class(cls):
+        print("SETUP")
+
+    def test_get_machine_info(self):
+        with mock.patch("os.path.isfile") as mock_isfile:
+            mock_isfile.return_value = True
+            open_mocked = mock.mock_open(read_data=MACHINE_CONF_CONTENTS)
+            with mock.patch("{}.open".format(BUILTINS), open_mocked):
+                result = device_info.get_machine_info()
+                assert result == EXPECTED_GET_MACHINE_INFO_RESULT
+                open_mocked.assert_called_once_with("/host/machine.conf")
+
+    def test_get_platform(self):
+        with mock.patch("sonic_py_common.device_info.get_machine_info") as get_machine_info_mocked:
+            get_machine_info_mocked.return_value = EXPECTED_GET_MACHINE_INFO_RESULT
+            result = device_info.get_platform()
+            assert result == "x86_64-mlnx_msn2700-r0"
+
+    @classmethod
+    def teardown_class(cls):
+        print("TEARDOWN")