python flask ModuleNotFoundError: No module named 'app'

对用户模型执行单元测试时报错

代码如下，请问怎么解决

from datetime import datetime,timedelta
import unittest
from app import app,db
from app.models import User,Post

class UserModelCase(unittest.TestCase):
	def setUp(self):
		app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
		db.create_all()

	def tearDown(self):
		db.session.remove()
		db.drop_all()

	def test_password_hashing(self):
		u = User(username='susan')
		u.set_password('cat')
		self.assertFalse(u.check_password('dog'))
		self.assertTrue(u.check_password('cat'))

	def test_avatar(self):
		u = User(username='john', email='[email protected]')
		self.assertEqual(u.avatar(128),('https://www.gravatar.com/avatar/'
										'd4c74594d841139328695756648b6bd6'
										'?d=identicon&s=128'))

	def test_follow(self):
		u1 = User(username='john', email='[email protected]')
		u2 = User(username='susan',email='[email protected]')
		db.session.add(u1)
		db.session.add(u2)
		db.session.commit()
		self.assertEqual(u1.followed.all(),[])
		self.assertEqual(u1,followers.all(),[])

		u1.follow(u2)
		db.session.commit()
		self.assertTrue(u1.is_following(u2))
		self.assertEqual(u1.followed.count(),1)
		self.assertEqual(u1.followed.first().username,'susan')
		self.assertEqual(u2.followers.count(),1)
		self.assertEqual(u2.followers.first().username,'john')

		u1.unfollow(u2)
		db.session.commit()
		self.assertFalse(u1.is_following(u2))
		self.assertEqual(u1.followed.count(), 0)
		self.assertEqual(u2.followers.count(), 0)

	def test_follow_posts(self):
		# create four users
		u1 = User(username='john', email='[email protected]')
		u2 = User(username='susan', email='[email protected]')
		u3 = User(username='mary', email='[email protected]')
		u4 = User(username='david', email='[email protected]')
		db.session.add_all([u1, u2, u3, u4])

		# create four posts
		now = datetime.utcnow()
		p1 = Post(body="post from john", author=u1,
				timestamp=now + timedelta(seconds=1))
		p2 = Post(body="post from susan", author=u2,
				timestamp=now + timedelta(seconds=4))
		p3 = Post(body="post from mary", author=u3,
				timestamp=now + timedelta(seconds=3))
		p4 = Post(body="post from david", author=u4,
				timestamp=now + timedelta(seconds=2))
		db.session.add_all([p1, p2, p3, p4])
		db.session.commit()

		# setup the followers
		u1.follow(u2)  # john follows susan
		u1.follow(u4)  # john follows david
		u2.follow(u3)  # susan follows mary
		u3.follow(u4)  # mary follows david
		db.session.commit()

		# check the followed posts of each user
		f1 = u1.followed_posts().all()
		f2 = u2.followed_posts().all()
		f3 = u3.followed_posts().all()
		f4 = u4.followed_posts().all()
		self.assertEqual(f1, [p2, p4, p1])
		self.assertEqual(f2, [p2, p3])
		self.assertEqual(f3, [p3, p4])
		self.assertEqual(f4, [p4])

if __name__ == '__main__':
	unittest.main(verbosity=2)