"Trying to unit test my code using unittest.mock python library".
I have code which is running database queries very similar to this:
app.py:
from flask import g
import mysql.connector
#app.route('/')
def create_table():
g.db=mysql.connector.connect("credentials")
cursor = g.db.cursor()
cursor.execute('CREATE TABLE IF NOT EXISTS test(id INT NOT NULL PRIMARY KEY, name VARCHAR(40),email VARCHAR(40) NOT NULL)')
cursor.close()
g.db.close()
I have mocked my g.db using the below method, but from here I am struggling with how to mock cursor.execute() and cursor.close(). Any help would be appreciated.
def testtable():
with patch('app.mysql.connector') as mock_mysql_connector:
create_table()
print g.db
#mock execute and close#
On printing g.db I'm getting Mock name and id, which I believe that means g.db is mocked, but I have no clue how I should mock execute() and close().
Do I have to do monkey patching?
If yes, please provide a hint how to monkey patch them?
If no, then what is another way to mock them?
You could use patch.multiple:
from mock import patch, DEFAULT
with patch.multiple('app', mysql=DEFAULT, g=DEFAULT) as dict:
# Mocking
connector = dict[̈́'mysql'].connector
db = connector.connect.return_value
cursor = db.cursor.return_value
# Run function to test
create_table()
# Assertions
assert dict['g'].db == db
db.close.assert_called_once_with()
cursor.close.assert_called_once_with()
connector.connect.assert_called_once_with("credentials")
Related
I have a python flask app which primarily uses sqlalchemy to execute all of it's mySQL queries and I need to write tests for it using a local database and behave.
After a brief research, the database I've chosen for this task is a local sqlite3 db, mainly because I've read that its pretty much compatible with mySQL and sqlalchemy, and also because it's easy to set up and tear-down.
I've established a connection to it successfully and managed to create all the tables I need for the tests.
I've encountered a problem when trying to execute some queries, where the query statement is being built as a sqlalchemy TextClause object and my sqlite3 connection cursor raises the following exception when trying to execute the statement:
TypeError: argument 1 must be str, not TextClause
How can I convert this TextClause object dynamically to a string and execute it?
I don't want to make drastic changes to the code just for testing.
A code example:
employees table:
id
name
1
Jeff Bezos
2
Bill Gates
from sqlalchemy import text
import sqlite3
def select_employee_by_id(id: int):
employees_table = 'employees'
db = sqlite3.connect(":memory:")
cursor = db.cursor()
with db as session:
statement = text("""
SELECT *
FROM {employees_table}
WHERE
id = :id
""".format(employees_table=employees_table)
).bindparams(id=id)
data = cursor.execute(statement)
return data.fetchone()
Should return a row containing {'id': 1, 'name': 'Jeff Bezos'} for select_employee_by_id(1)
Thanks in advance!
If you want to test your TextClause query then you should execute it by using SQLAlchemy, not by using a DBAPI (SQLite) cursor:
from sqlalchemy import create_engine, text
def select_employee_by_id(id: int):
employees_table = 'employees'
engine = create_engine("sqlite://")
with engine.begin() as conn:
statement = text("""
SELECT *
FROM {employees_table}
WHERE
id = :id
""".format(employees_table=employees_table)
).bindparams(id=id)
data = conn.execute(statement)
return data.one()
I have a file with two functions that I must test that look like this:
def create_conn(config):
conn = psycopg2.connect(dbname = config['dbname'], ...)
return conn
def use_conn():
conn = create_conn(CONSTANT_CONFIG)
with conn.cursor() as cursor:
cursor.execute("some sql query")
conn.close()
I've been able to create pytest fixtures for testing functions that use DynamoDB and S3 with a mock database using moto that essentially overrides any call to boto3 like below:
# in conftest.py
#pytest.fixture()
def s3_client(aws_credentials):
with moto.mock_s3()
client = boto3.client('s3')
yield client
# in test file
def test_func(s3_client):
func() # a function that uses boto3
But I can't come across any examples that do something similar for PostgresSQL databases. Is there anyway to essentially override psycopg2.connect() to return a connection to a mock database? I think pytest-postgresql might help, but I couldn't find any code examples.
I write some tests with pytest, I want to test create user and email with post method.
With some debug, I know the issue is I open two databases in memory, but they are same database SessionLocal().
So how can I fix this, I try db.flush(), but it doesn't work.
this is the post method code
#router.post("/", response_model=schemas.User)
def create_user(
*,
db: Session = Depends(deps.get_db), #the get_db is SessionLocal()
user_in: schemas.UserCreate,
current_user: models.User = Depends(deps.get_current_active_superuser),
) -> Any:
"""
Create new user.
"""
user = crud.user.get_by_email(db, email=user_in.email)
if user:
raise HTTPException(
status_code=400,
detail="The user with this username already exists in the system.",
)
user = crud.user.create(db, obj_in=user_in)
print("====post====")
print(db.query(models.User).count())
print(db)
if settings.EMAILS_ENABLED and user_in.email:
send_new_account_email(
email_to=user_in.email, username=user_in.email, password=user_in.password
)
return user
and the test code is:
def test_create_user_new_email(
client: TestClient, superuser_token_headers: dict, db: Session # db is SessionLocal()
) -> None:
username = random_email()
password = random_lower_string()
data = {"email": username, "password": password}
r = client.post(
f"{settings.API_V1_STR}/users/", headers=superuser_token_headers, json=data,
)
assert 200 <= r.status_code < 300
created_user = r.json()
print("====test====")
print(db.query(User).count())
print(db)
user = crud.user.get_by_email(db, email=username)
assert user
assert user.email == created_user["email"]
and the test result is
> assert user
E assert None
====post====
320
<sqlalchemy.orm.session.Session object at 0x7f0a9f660910>
====test====
319
<sqlalchemy.orm.session.Session object at 0x7f0aa09c4d60>
Your code does not provide enough information to help you, the key issues are probably in what is hidden and explained by your comments.
And it seems like you are confusing sqlalchemy session and databases. If you are not familiar with these concepts, I highly recommend you to have a look at SQLAlchemy documentation.
But, looking at your code structure, it seems like you are using FastAPI.
Then, if you want to test SQLAlchemy with pytest, I recommend you to use pytest fixture with SQL transactions.
Here is my suggestion on how to implement such a test. I'll suppose that you want to run the test on your actual database and not create a new database especially for the tests. This implementation is heavily based on this github gist (the author made a "feel free to use statement", so I suppose he is ok with me copying his code here):
# test.py
import pytest
from sqlalchemy import create_engine
from sqlalchemy.orm import Session
from fastapi.testclient import TestClient
from myapp.models import BaseModel
from myapp.main import app # import your fastapi app
from myapp.database import get_db # import the dependency
client = TestClient(app)
# scope="session" mean that the engine will last for the whole test session
#pytest.fixture(scope="session")
def engine():
return create_engine("postgresql://localhost/test_database")
# at the end of the test session drops the created metadata using fixture with yield
#pytest.fixture(scope="session")
def tables(engine):
BaseModel.metadata.create_all(engine)
yield
BaseModel.metadata.drop_all(engine)
# here scope="function" (by default) so each time a test finished, the database is cleaned
#pytest.fixture
def dbsession(engine, tables):
"""Returns an sqlalchemy session, and after the test tears down everything properly."""
connection = engine.connect()
# begin the nested transaction
transaction = connection.begin()
# use the connection with the already started transaction
session = Session(bind=connection)
yield session
session.close()
# roll back the broader transaction
transaction.rollback()
# put back the connection to the connection pool
connection.close()
## end of the gist.github code
#pytest.fixture
def db_fastapi(dbsession):
def override_get_db():
db = dbsession
try:
yield db
finally:
db.close()
client.app.dependency_overrides[get_db] = override_get_db
yield db
# Now you can run your test
def test_create_user_new_email(db_fastapi):
username = random_email()
# ...
I'm writing some Pytest code using a sqlite db, to test some logic. I setup a root level fixture to instantiate a db engine:
class SqliteEngine:
def __init__(self):
self._conn_engine = create_engine("sqlite://")
self._conn_engine.execute("pragma foreign_keys=ON")
def get_engine(self):
return self._conn_engine
def get_session(self):
Session = sessionmaker(bind=self._conn_engine, autoflush=True)
return Session()
#pytest.fixture(scope="session")
def sqlite_engine():
sqlite_engine = SqliteEngine()
return sqlite_engine
Then in my test class, I have
class TestRbac:
#pytest.fixture(scope="class")
def setup_rbac_tables(self, sqlite_engine):
conn_engine = sqlite_engine.get_engine()
conn_engine.execute("attach ':memory:' as rbac")
Application.__table__.create(conn_engine)
Client.__table__.create(conn_engine)
Role.__table__.create(conn_engine)
session = sqlite_engine.get_session()
application = Application(id=1, name="test-application")
session.add(application)
session.flush()
client = Client(id=0, name="Test", email_pattern="")
session.add(client)
session.flush()
Finally in the test in that class, I tried
def test_query_config_data_default(self, sqlite_engine, setup_rbac_tables, rbac):
conn_engine = sqlite_engine.get_engine()
session = sqlite_engine.get_session()
client = Client(id=1, name=factory.Faker("name").generate(), email_pattern="")
session.add(client)
session.flush()
clients = sqlite_engine.get_session().query(Client).all()
for client in clients:
print(client.id, client.name)
However, only one client prints (and if I try for Application, none print), and I can't figure out why. Is this a problem with the fixture scopes? Or the engine? Or how sqlite works in pytest?
I'm not an expert on this but I think you need to define the fixture in such a way that the session is shared unless you plan to commit in each fixture. In setup_rbac_tables the session is destroyed with the function scope. And when get_session is called again a new session is created.
In my pytest sqlalchemy tests I do something like this, where the db fixture is a db session that is reused between fixtures and in the test:
#pytest.fixture
def customer_user(db):
from ..model.user import User
from ..model.auth import Group
group = db.query(Group).filter(
Group.name == 'customer').first()
if not group:
group = Group(name='customer', label='customer')
user = User(email=test_email_fmt.format(uuid4().hex), group=group)
db.add(user)
return user
I am trying to test by mocking a database query, but receiving an error:
Asssertion error:AssertionError: Expected call: execute()
Not called
and create_table() not defined.
I want to execute() to be called and use create_table() to return response for asserting against pre-defined values.
app.py
from flask import Flask,g
#app.before_request
def before_request():
g.db = mysql.connector.connect(user='root', password='root', database='mysql')
def create_table():
try:
cur = g.db.cursor() #here g is imported form Flask module
cursor.execute ('CREATE TABLE IF NOT EXISTS Man (id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, name VARCHAR(40)')
data = dict(Table='Man is created')
resp = jsonify(data)
cursor.close()
return resp
test.py
import unittest
from app import *
from mock import patch
class Test(unittest.TestCase):
def test_create(self):
with patch("app.g") as mock_g:
mock_g.db.cursor()
mock_g.execute.assert_called_with()
resp = create_table()
assertEqual(json, '{"Table":"Testmysql is created","Columns": ["id","name","email"]}')
What am I doing wrong?Can someone please tell me how to fix it
I believe you need to add your changes before closing the cursor, or the execute won't occur. Try adding cursor.commit() before (or instead of) cursor.close().