Database Testing

Database Testing

Quick DB Testing Checklist:

• Schema matches specification
• Unique constraints prevent duplicates
• Foreign keys prevent orphaned records
• Migrations are reversible
• Transactions roll back on error

Critical Success Factors:

• Database bugs cause data loss/corruption (catastrophic)
• Test migrations in staging before production
• Transaction tests catch concurrency bugs

Quick Reference Card

When to Use

• New table/schema creation
• Migration development
• Data integrity validation
• Query performance optimization

Database Test Types

Schema Testing

test('users table has correct schema', async () => {
  const schema = await db.raw(`
    SELECT column_name, data_type, is_nullable
    FROM information_schema.columns
    WHERE table_name = 'users'
  `);

  expect(schema).toContainEqual({
    column_name: 'id',
    data_type: 'integer',
    is_nullable: 'NO'
  });

  expect(schema).toContainEqual({
    column_name: 'email',
    data_type: 'character varying',
    is_nullable: 'NO'
  });
});

Data Integrity Testing

test('email must be unique', async () => {
  await db.users.create({ email: 'test@example.com' });

  await expect(
    db.users.create({ email: 'test@example.com' })
  ).rejects.toThrow('unique constraint violation');
});

test('foreign key prevents orphaned records', async () => {
  const user = await db.users.create({ email: 'test@example.com' });
  await db.orders.create({ userId: user.id, total: 100 });

  await expect(
    db.users.delete({ id: user.id })
  ).rejects.toThrow('foreign key constraint');
});

Migration Testing

test('migration is reversible', async () => {
  await migrate('add-users-table');

  // Table exists after migration
  const tables = await db.raw(`SELECT table_name FROM information_schema.tables`);
  expect(tables.map(t => t.table_name)).toContain('users');

  await rollback('add-users-table');

  // Table gone after rollback
  const tablesAfter = await db.raw(`SELECT table_name FROM information_schema.tables`);
  expect(tablesAfter.map(t => t.table_name)).not.toContain('users');
});

test('migration preserves existing data', async () => {
  await db.users.create({ email: 'test@example.com' });

  await migrate('add-age-column');

  const user = await db.users.findOne({ email: 'test@example.com' });
  expect(user).toBeDefined();
  expect(user.age).toBeNull(); // New column, null default
});

Transaction Testing

test('transaction rolls back on error', async () => {
  const initialCount = await db.users.count();

  try {
    await db.transaction(async (trx) => {
      await trx('users').insert({ email: 'user1@example.com' });
      await trx('users').insert({ email: 'user2@example.com' });
      throw new Error('Rollback test');
    });
  } catch (error) { /* Expected */ }

  expect(await db.users.count()).toBe(initialCount);
});

test('concurrent transactions isolated', async () => {
  const user = await db.users.create({ balance: 100 });

  // Two concurrent withdrawals (race condition test)
  await Promise.all([
    db.transaction(async (trx) => {
      const current = await trx('users').where({ id: user.id }).first();
      await trx('users').update({ balance: current.balance - 50 });
    }),
    db.transaction(async (trx) => {
      const current = await trx('users').where({ id: user.id }).first();
      await trx('users').update({ balance: current.balance - 50 });
    })
  ]);

  const final = await db.users.findOne({ id: user.id });
  expect(final.balance).toBe(0); // Proper isolation
});

Agent-Driven Database Testing

// Generate test data with integrity
await Task("Generate Test Data", {
  schema: 'ecommerce',
  tables: ['users', 'products', 'orders'],
  count: { users: 1000, products: 500, orders: 5000 },
  preserveReferentialIntegrity: true
}, "qe-test-data-architect");

// Test migration safety
await Task("Migration Test", {
  migration: 'add-payment-status-column',
  tests: ['forward', 'rollback', 'data-preservation'],
  environment: 'staging'
}, "qe-test-executor");

Agent Coordination Hints

Memory Namespace

aqe/database-testing/
├── schema-snapshots/*   - Current schema state
├── migrations/*         - Migration test results
├── integrity/*          - Constraint validation
└── performance/*        - Query benchmarks

Fleet Coordination

const dbFleet = await FleetManager.coordinate({
  strategy: 'database-testing',
  agents: [
    'qe-test-data-architect',  // Generate test data
    'qe-test-executor',        // Run DB tests
    'qe-performance-tester'    // Query performance
  ],
  topology: 'sequential'
});

Related Skills

• test-data-management - Generate test data
• performance-testing - Query performance
• compliance-testing - Data protection

Remember

Test migrations before production: Forward works, rollback works, data preserved, performance acceptable. Never deploy untested migrations.

With Agents: qe-test-data-architect generates realistic test data with referential integrity. qe-test-executor validates migrations automatically in CI/CD.

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