Database migration testing in Testing Fundamentals - Test Execution Trace

Test Overview

This test verifies that data is correctly migrated from the old database schema to the new schema without loss or corruption. It checks that all expected tables and records exist after migration.

Test Code - unittest

Testing Fundamentals

import unittest
import sqlite3

class TestDatabaseMigration(unittest.TestCase):
    def setUp(self):
        # Connect to old and new databases
        self.old_db = sqlite3.connect(':memory:')
        self.new_db = sqlite3.connect(':memory:')
        self.create_old_schema()
        self.create_new_schema()
        self.insert_old_data()
        self.perform_migration()

    def create_old_schema(self):
        cursor = self.old_db.cursor()
        cursor.execute('CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)')
        self.old_db.commit()

    def create_new_schema(self):
        cursor = self.new_db.cursor()
        cursor.execute('CREATE TABLE users (user_id INTEGER PRIMARY KEY, full_name TEXT, age INTEGER)')
        self.new_db.commit()

    def insert_old_data(self):
        cursor = self.old_db.cursor()
        cursor.execute('INSERT INTO users (name, age) VALUES (?, ?)', ('Alice', 30))
        cursor.execute('INSERT INTO users (name, age) VALUES (?, ?)', ('Bob', 25))
        self.old_db.commit()

    def perform_migration(self):
        old_cursor = self.old_db.cursor()
        new_cursor = self.new_db.cursor()
        old_cursor.execute('SELECT id, name, age FROM users')
        rows = old_cursor.fetchall()
        for row in rows:
            new_cursor.execute('INSERT INTO users (user_id, full_name, age) VALUES (?, ?, ?)', row)
        self.new_db.commit()

    def test_data_migrated_correctly(self):
        new_cursor = self.new_db.cursor()
        new_cursor.execute('SELECT user_id, full_name, age FROM users ORDER BY user_id')
        migrated_rows = new_cursor.fetchall()
        expected = [(1, 'Alice', 30), (2, 'Bob', 25)]
        self.assertEqual(migrated_rows, expected)

    def tearDown(self):
        self.old_db.close()
        self.new_db.close()

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

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts and sets up in-memory old and new databases	Two empty in-memory SQLite databases are created with old and new schemas	-	PASS
2	Insert sample data into old database's users table	Old database users table contains two records: Alice (30), Bob (25)	-	PASS
3	Perform migration by copying data from old to new database with new schema	New database users table populated with migrated records matching old data	-	PASS
4	Query new database users table and compare data to expected records	New database users table has records: (1, 'Alice', 30), (2, 'Bob', 25)	Assert that migrated data equals expected data [(1, 'Alice', 30), (2, 'Bob', 25)]	PASS
5	Close database connections and end test	Databases closed, test ends cleanly	-	PASS

Failure Scenario

Failing Condition: Data is missing or incorrectly migrated in the new database

Execution Trace Quiz - 3 Questions

What does the test verify after migration?

A That all user records are copied correctly to the new database

B That the old database schema is deleted

C That the new database is empty

D That the database connection is closed

Key Result

Always verify that data migrated to the new database matches exactly the expected records to catch any loss or corruption during migration.