pytest-django for Django testing - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this pytest-django test?

Consider this Django model and pytest-django test. What will be the test result?

PyTest

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)

import pytest

@pytest.mark.django_db
def test_book_creation():
    book = Book.objects.create(title='Test Driven Development')
    assert Book.objects.count() == 1
    assert book.title == 'Test Driven Development'

A Test fails because assertion count is wrong

B Test fails because database access is not allowed

C Test raises AttributeError due to missing model

D Test passes successfully

💡 Hint

Remember to use @pytest.mark.django_db to allow database access in tests.

The test uses @pytest.mark.django_db which enables database access. The Book is created and counted correctly, so assertions pass.

❓ assertion

intermediate

Which assertion correctly checks the response status code in pytest-django?

You have a Django view that returns HTTP 200. Which assertion correctly verifies this in a pytest-django test?

PyTest

import pytest
from django.urls import reverse

@pytest.mark.django_db
def test_homepage(client):
    url = reverse('home')
    response = client.get(url)
    # Which assertion is correct here?

A assert response.status_code == 200

B assert response.code == 200

C assert response.status == 200

D assert response.status_code is '200'

💡 Hint

Check the attribute name for HTTP status code in Django test responses.

The correct attribute is response.status_code which holds an integer HTTP status code. Using '==' compares values correctly.

🔧 Debug

advanced

Why does this pytest-django test raise an error?

This test tries to create a Django user but raises an error. Identify the cause.

PyTest

import pytest
from django.contrib.auth.models import User

@pytest.mark.django_db
def test_create_user():
    user = User.objects.create(username='tester')
    assert User.objects.count() == 1
    assert user.username == 'tester'

# Error: django.db.utils.IntegrityError: NOT NULL constraint failed: auth_user.password

A Test fails because User model is not imported

B User creation fails because password field is required and missing

C Test fails because @pytest.mark.django_db is missing

D User creation fails because username is not unique

💡 Hint

Check required fields for Django's User model when creating users.

Django's User model requires a password field. Creating a user without password causes IntegrityError due to NOT NULL constraint.

❓ framework

advanced

Which pytest-django fixture provides a test client with database access?

You want to test Django views with database access in pytest. Which fixture should you use?

A django_client

B db_client

C client

D transactional_db_client

💡 Hint

pytest-django provides a built-in fixture for HTTP client with DB access.

The 'client' fixture in pytest-django provides a Django test client with database access enabled when @pytest.mark.django_db is used.

🧠 Conceptual

expert

What happens if you omit @pytest.mark.django_db in a test that accesses the database?

In pytest-django, what is the result of running a test that queries the database but does NOT have @pytest.mark.django_db?

A Test raises RuntimeError about database access not allowed

B Test runs successfully but database changes are not saved

C Test silently skips database queries

D Test raises django.core.exceptions.ImproperlyConfigured error

💡 Hint

pytest-django restricts database access unless explicitly allowed.

pytest-django raises a RuntimeError if a test accesses the database without @pytest.mark.django_db to prevent accidental DB usage.

Practice

1. What is the main purpose of using @pytest.mark.django_db in pytest-django tests?

easy

A. To skip the test when the database is not available

B. To disable database migrations during the test

C. To mark the test as a slow test

D. To allow the test to access and modify the Django database

Solution

1. Step 1: Understand the role of @pytest.mark.django_db

   This marker tells pytest that the test needs database access, so pytest sets up the test database properly.

2. Step 2: Identify what happens without the marker

   Without this marker, tests cannot access or modify the database and will fail if they try.

3. Final Answer:

   To allow the test to access and modify the Django database -> Option D

4. Quick Check:

   Database access marker = B [OK]

Hint: Use @pytest.mark.django_db to enable DB access in tests [OK]

Common Mistakes:

• Thinking it skips tests instead of enabling DB access
• Confusing it with marking tests as slow
• Assuming it disables migrations

2. Which of the following is the correct way to use the Django test client fixture in pytest-django?

easy

A. def test_view(client): response = client.get('/'); assert response.status_code == 200

B. def test_view(): response = client.get('/'); assert response.status_code == 200

C. def test_view(client): response = client.post('/'); assert response.status_code = 200

D. def test_view(client): response = client.get('/'); assert response.status == 200

Solution

1. Step 1: Check the function signature and usage

   The test function must accept the client fixture as a parameter to use it.

2. Step 2: Verify the assertion syntax

   The assertion must use == to compare response.status_code to 200.

3. Final Answer:

   def test_view(client): response = client.get('/'); assert response.status_code == 200 -> Option A

4. Quick Check:

   Correct fixture use and assertion = C [OK]

Hint: Pass client as parameter and use response.status_code == 200 [OK]

Common Mistakes:

• Not passing client as a parameter
• Using single = instead of == in assertion
• Checking response.status instead of response.status_code

3. Given the following test code using pytest-django, what will be the output when running the test?

import pytest
from django.contrib.auth.models import User

@pytest.mark.django_db
def test_user_count():
    User.objects.create(username='alice')
    User.objects.create(username='bob')
    count = User.objects.count()
    assert count == 2
    print(count)

medium

A. Test fails because count is 0

B. Test passes and prints 2

C. Test raises a database error

D. Test passes but prints 0

Solution

1. Step 1: Analyze database access and object creation

   The test uses @pytest.mark.django_db, so it can create User objects in the test database.

2. Step 2: Count the User objects and assert

   Two users are created, so User.objects.count() returns 2, matching the assertion.

3. Final Answer:

   Test passes and prints 2 -> Option B

4. Quick Check:

   User count = 2 [OK]

Hint: Mark test with django_db to create and count users correctly [OK]

Common Mistakes:

• Forgetting @pytest.mark.django_db causes DB errors
• Assuming count is zero without creation
• Confusing print output with test result

4. Identify the error in this pytest-django test code and how to fix it:

def test_create_user():
    User.objects.create(username='charlie')
    assert User.objects.count() == 1

medium

A. Test function name should start with 'test_'

B. User model is not imported

C. Missing @pytest.mark.django_db decorator to allow DB access

D. Assertion should check for 0 instead of 1

Solution

1. Step 1: Check database access requirement

   The test tries to create a User in the database but lacks @pytest.mark.django_db, so DB access is not allowed.

2. Step 2: Fix by adding the missing decorator

   Adding @pytest.mark.django_db above the test function enables database access and fixes the error.

3. Final Answer:

   Missing @pytest.mark.django_db decorator to allow DB access -> Option C

4. Quick Check:

   DB access decorator missing = D [OK]

Hint: Add @pytest.mark.django_db to tests using the database [OK]

Common Mistakes:

• Not adding the django_db marker
• Assuming import errors without checking imports
• Misunderstanding assertion values

5. You want to test a Django view that requires a logged-in user using pytest-django. Which is the best way to simulate a logged-in user in your test?

hard

A. Use the client.force_login(user) method after creating a user in the test database

B. Set a session variable manually without creating a user

C. Call the view function directly without using the client fixture

D. Use @pytest.mark.django_db without logging in the user

Solution

1. Step 1: Understand how to simulate login in pytest-django

   The client.force_login(user) method logs in the user for the test client session.

2. Step 2: Create a user in the test database first

   You must create a user in the test database (with @pytest.mark.django_db) before calling force_login.

3. Final Answer:

   Use the client.force_login(user) method after creating a user in the test database -> Option A

4. Quick Check:

   Use force_login with created user = A [OK]

Hint: Create user and call client.force_login(user) to simulate login [OK]

Common Mistakes:

• Trying to set session manually without user
• Calling views directly without client
• Forgetting to create user before login