added flask app and test cases

Jenkinsfile

@@ -0,0 +1,20 @@
+pipeline {
+  agent { docker { image 'python:3.7.2' } }
+  stages {
+    stage('build') {
+      steps {
+        sh 'pip install -r requirements.txt'
+      }
+    }
+    stage('test') {
+      steps {
+        sh 'python test_app.py'
+      }   
+      post {
+        always {
+          junit 'test-reports/*.xml'
+        }
+      }  
+    }
+  }
+}

app.py

@@ -0,0 +1,14 @@
+from flask import Flask
+app = Flask(__name__)
+
+@app.route('/')
+@app.route('/hello/')
+def hello_world():
+    return 'Hello World!\n'
+
+@app.route('/hello/<username>') # dynamic route
+def hello_user(username):
+    return 'Why Hello %s!\n' % username
+
+if __name__ == '__main__':
+    app.run(host='0.0.0.0')     # open for everyone

requirements.txt

@@ -0,0 +1,9 @@
+Click==7.0
+Flask==1.0.2
+itsdangerous==1.1.0
+Jinja2==2.10
+MarkupSafe==1.1.0
+Werkzeug==0.14.1
+xmlrunner==1.7.7
+# pytest==6.1.2  
+# pytest-cov==2.10.1 

test_app.py

@@ -0,0 +1,31 @@
+import unittest
+import app
+
+class TestHello(unittest.TestCase):
+
+    def setUp(self):
+        app.app.testing = True
+        self.app = app.app.test_client()
+
+    def test_hello(self):
+        rv = self.app.get('/')
+        self.assertEqual(rv.status, '200 OK')
+        self.assertEqual(rv.data, b'Hello World!\n')
+
+    def test_hello_hello(self):
+        rv = self.app.get('/hello/')
+        self.assertEqual(rv.status, '200 OK')
+        self.assertEqual(rv.data, b'Hello World!\n')
+
+    def test_hello_name(self):
+        name = 'Simon'
+        rv = self.app.get(f'/hello/{name}')
+        self.assertEqual(rv.status, '200 OK')
+        self.assertIn(bytearray(f"{name}", 'utf-8'), rv.data)
+
+if __name__ == '__main__':
+    ############# Add these lines #############
+    import xmlrunner
+    runner = xmlrunner.XMLTestRunner(output='test-reports')
+    unittest.main(testRunner=runner)
+    ###########################################