Add macOS environment to CI pipeline

azure-pipelines.yml

 jobs:
 
-- job: 'Install_through_source_code'
+- job: 'Ubuntu_16_04'
   pool:
     vmImage: 'Ubuntu 16.04'
   strategy:
@@ -21,4 +21,27 @@ jobs:
   - script: |
       cd test
       PATH=$HOME/.local/bin:$PATH python3 sdk_test.py
+    displayName: 'Built-in tuner tests'
+
+- job: 'macOS_10_13'
+  pool:
+    vmImage: 'macOS 10.13'
+  strategy:
+    matrix:
+      Python36:
+        PYTHON_VERSION: '3.6'
+
+  steps:
+  - script: python3 -m pip install --upgrade pip setuptools
+    displayName: 'Install python tools'
+  - script: |
+      source install.sh
+    displayName: 'Install nni toolkit via source code'
+  - script: |
+      cd test
+      PATH=$HOME/Library/Python/3.7/bin:$PATH python3 naive_test.py
+    displayName: 'Integration tests'
+  - script: |
+      cd test
+      PATH=$HOME/Library/Python/3.7/bin:$PATH python3 sdk_test.py
     displayName: 'Built-in tuner tests'
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