Why database testing ensures data integrity in Testing Fundamentals - Test Execution Impact

Test Overview

This test checks that data saved in the database matches what was input through the application. It verifies that no data is lost or changed incorrectly, ensuring data integrity.

Test Code - unittest

Testing Fundamentals

import sqlite3
import unittest

class TestDatabaseIntegrity(unittest.TestCase):
    def setUp(self):
        self.conn = sqlite3.connect(':memory:')
        self.cursor = self.conn.cursor()
        self.cursor.execute('''CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)''')

    def test_insert_and_retrieve(self):
        # Insert data
        self.cursor.execute('INSERT INTO users (name, age) VALUES (?, ?)', ('Alice', 30))
        self.conn.commit()

        # Retrieve data
        self.cursor.execute('SELECT name, age FROM users WHERE name = ?', ('Alice',))
        row = self.cursor.fetchone()

        # Assert data integrity
        self.assertIsNotNone(row)
        self.assertEqual(row[0], 'Alice')
        self.assertEqual(row[1], 30)

    def tearDown(self):
        self.conn.close()

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

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts and in-memory database is created with users table	Empty database with users table ready	-	PASS
2	Insert user data ('Alice', 30) into users table	Database contains one user record with name 'Alice' and age 30	-	PASS
3	Retrieve user data where name is 'Alice'	Query returns one record with name 'Alice' and age 30	Check that retrieved data is not None	PASS
4	Assert retrieved name equals 'Alice'	Retrieved data name field is 'Alice'	AssertEqual(row[0], 'Alice')	PASS
5	Assert retrieved age equals 30	Retrieved data age field is 30	AssertEqual(row[1], 30)	PASS
6	Test ends and database connection is closed	Database connection closed	-	PASS

Failure Scenario

Failing Condition: Data inserted does not match data retrieved (e.g., wrong age or missing record)

Execution Trace Quiz - 3 Questions

What does the test verify about the data in the database?

A That the database connection is slow

B That the database schema is empty

C That the data retrieved matches the data inserted

D That the application UI is responsive

Key Result

Always verify that data saved in the database can be retrieved exactly as expected to ensure data integrity.