MongoDB Transactions Fail in Tests: MongoMemoryServer Needs Replica Set Configuration

[seanspeaks]

Problem

Tests are failing with MongoDB transaction errors when using Prisma operations:

PrismaClientKnownRequestError: 
Invalid `prisma.credential.deleteMany()` invocation

Raw query failed. Code: `unknown`. 
Message: `Kind: Transactions are not supported by this deployment, labels: {}`

Root Cause

MongoDB requires a replica set to support transactions. Our test setup uses mongodb-memory-server (standalone mode) which doesn't support transactions by default.

Current Setup (packages/test/mongodb.js):

async start() {
    this.#mongoServer = await MongoMemoryServer.create();
    process.env.MONGO_URI = this.#mongoServer.getUri();
}

This creates a standalone MongoDB instance which doesn't support:

• Multi-document transactions
• $transaction operations
• Prisma's automatic transaction wrapping for batch operations

Why This Matters

1. Prisma automatically wraps batch operations in transactions:

   • deleteMany(), updateMany(), createMany()
   • Operations within Prisma Client Extensions (like our encryption extension)

2. Tests fail that use legitimate Prisma patterns:

   // This fails in tests but works in production
   await prisma.credential.deleteMany({ 
       where: { externalId: { startsWith: 'test-' } } 
   });

3. Production uses MongoDB with replica sets (AWS DocumentDB, MongoDB Atlas)

   • Tests don't match production environment
   • False confidence in test suite

Migration Context

We're in the middle of migrating from Mongoose to Prisma:

• Old code: Uses Mongoose models and connections
• New code: Uses Prisma client with field-level encryption
• Hybrid state: Both systems coexist, causing conflicts

Evidence of migration in progress:

• packages/core/database/mongoose.js - Legacy Mongoose setup
• packages/core/database/prisma.js - New Prisma client
• packages/core/database/models/ - Old Mongoose models still in use
• packages/core/database/repositories/health-check-repository-mongodb.js - Uses mongoose.connection

Affected Test Files

Tests using Prisma with batch operations fail:

• ✗ database/encryption/encryption-integration.test.js - All cleanup operations
• ✗ database/encryption/mongo-decryption-fix-verification.test.js
• ✗ database/encryption/postgres-decryption-fix-verification.test.js
• ✗ user/tests/user-password-encryption-isolation.test.js

Solution

Option 1: Enable Replica Set in MongoMemoryServer (Recommended)

Update packages/test/mongodb.js:

const { MongoMemoryReplSet } = require('mongodb-memory-server');

class TestMongo {
    #mongoServer;

    async start() {
        // Create replica set instead of standalone
        this.#mongoServer = await MongoMemoryReplSet.create({
            replSet: { 
                count: 1,  // Single node replica set (sufficient for tests)
                storageEngine: 'wiredTiger'
            }
        });
        
        const uri = this.#mongoServer.getUri();
        process.env.MONGO_URI = uri;
        
        console.log('Started in-memory MongoDB replica set', uri);
    }

    async stop() {
        await this.#mongoServer.stop();
        process.env.MONGO_URI = undefined;
        this.#mongoServer = undefined;
    }
}

Benefits:

• Enables transaction support
• Better matches production environment
• Fixes all Prisma batch operation tests
• No changes needed to test code

Option 2: Disable Prisma Transactions in Tests (Not Recommended)

Configure Prisma to skip transactions:

// Not ideal - tests wouldn't match production behavior
const prisma = new PrismaClient({
    transactionOptions: {
        maxWait: 5000,
        timeout: 10000,
        isolationLevel: 'ReadUncommitted'
    }
});

This doesn't actually disable transactions, just configures them differently.

Additional Work: Complete Mongoose → Prisma Migration

While fixing the test setup, we should complete the migration:

Current Hybrid State Issues:

1. Two database clients initialized (mongoose + prisma)
2. Connection state checks use Mongoose (mongoose.connection.readyState)
3. Schema initialization uses Mongoose (ensureCollectionsExist)
4. Legacy models in database/models/ still imported

Complete Migration Tasks:

• Replace all mongoose.connection.* with Prisma equivalents
• Remove database/mongoose.js and legacy connection logic
• Migrate database/models/*.js Mongoose models to Prisma schema
• Update health-check-repository-mongodb.js to use Prisma connection checks
• Remove Mongoose dependency from package.json once fully migrated
• Update mongodb-schema-init.js to use Prisma schema inspection instead of Mongoose

Benefits of Completing Migration:

• Single source of truth for database operations
• Consistent encryption across all models
• Better type safety with Prisma
• Reduced complexity (no dual connection management)
• Modern ORM patterns and tooling

Testing the Fix

After implementing Option 1:

# Should pass all encryption tests
npm test -- database/encryption/

# Verify transaction support
npm test -- database/encryption/encryption-integration.test.js

# Check cleanup operations work
npm test -- user/tests/user-password-encryption-isolation.test.js

References

• Prisma Transactions Docs
• mongodb-memory-server Replica Set Guide
• MongoDB Transactions Requirements

Related Files

Test Infrastructure:

• packages/test/mongodb.js - MongoMemoryServer setup (needs replica set)
• packages/test/jest-global-setup.js - Jest test setup
• packages/core/jest-setup.js - Core package test setup

Affected by Mongoose/Prisma Hybrid:

• packages/core/database/prisma.js - Prisma client with encryption
• packages/core/database/mongoose.js - Legacy Mongoose connection
• packages/core/database/utils/mongodb-schema-init.js - Uses Mongoose connection
• packages/core/database/repositories/health-check-repository-mongodb.js - Uses Mongoose

---

Priority: High - Blocking test suite reliability
Category: Testing Infrastructure, Database Migration
Affects: All Prisma-based tests using batch operations