Solutions - Mocking the database access

import os
import sys
root = os.path.dirname( os.path.dirname( os.path.abspath(__file__) ))
sys.path.insert(0, os.path.join(root, 'exdb'))
import pytest


import db
from bank import Bank


class MockDB(object):
    def create(self):
        self.db = {}

    def get(self, name):
        return self.db.get(name)

    def insert(self, name, amount):
        self.db[name] = amount

    def update(self, name, amount):
        self.db[name] = amount


db.DB = MockDB

def test_app(tmpdir):
    app = Bank()
    app.setup()
    assert app.status('foo') == None
    assert app.status('bar') == None

    app.deposit('foo', 100)
    assert app.status('foo') == 100

    app.deposit('foo', 10)
    assert app.status('foo') == 110

    app.deposit('bar', 130)
    assert app.status('foo') == 110
    assert app.status('bar') == 130

    app.transfer('foo', 'bar', 19)
    assert app.status('foo') == 91
    assert app.status('bar') == 149

    with pytest.raises(Exception) as exinfo:
        app.transfer('foo', 'bar', 200)
    assert exinfo.type == Exception
    assert str(exinfo.value) == 'Not enough money'