@romatech/orm-providers-memory

@romatech/orm-providers-memory

In-memory provider for @romatech/orm.

Ideal for unit tests, integration tests, and rapid prototyping without spinning up a real database.

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Installation

npm install @romatech/orm @romatech/orm-providers-memory reflect-metadata

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Quick Start

import 'reflect-metadata';
import { DbContext, DbContextOptions, Entity, PrimaryKey, Column } from '@romatech/orm';
import { MemoryProvider } from '@romatech/orm-providers-memory';

@Entity('Users')
class User {
    @PrimaryKey() id!: number;
    @Column() name!: string;
    @Column() email!: string;
}

class TestDbContext extends DbContext {
    users = this.set(User);

    constructor() {
        super(new DbContextOptions().useProvider(new MemoryProvider()));
    }
}

// In your test
const db = new TestDbContext();

db.users.add({ id: 1, name: 'Alice', email: 'alice@example.com' });
await db.saveChanges();

const users = await db.users.ToList();
console.log(users); // [{ id: 1, name: 'Alice', email: 'alice@example.com' }]

const alice = await db.users.FirstOrDefault(u => u.name === 'Alice');
console.log(alice?.email); // 'alice@example.com'

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How It Works

The MemoryProvider stores entities in plain JavaScript Map and Array structures. All operations (add, update, remove, query) happen synchronously in memory — no I/O.

Features:

• Primary key uniqueness enforcement
• Full QueryBuilder support (where, orderBy, skip, take, select, etc.)
• Migration history tracking (in-memory)
• Schema management (createTable, dropTable, addColumn, removeColumn)
• clear() method to reset all data between tests

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Usage in Tests

Creating a fresh context per test

describe('UserService', () => {
    let db: TestDbContext;

    beforeEach(() => {
        db = new TestDbContext(); // fresh in-memory database each time
    });

    it('should create a user', async () => {
        db.users.add({ id: 1, name: 'Bob', email: 'bob@x.com' });
        await db.saveChanges();

        const count = await db.users.Count();
        expect(count).toBe(1);
    });

    it('should query users by name', async () => {
        db.users.addRange([
            { id: 1, name: 'Alice', email: 'a@x.com' },
            { id: 2, name: 'Bob', email: 'b@x.com' }
        ]);
        await db.saveChanges();

        const result = await db.users
            .Where(u => u.name === 'Alice')
            .FirstOrDefault();

        expect(result?.email).toBe('a@x.com');
    });
});

Resetting state

If you share a provider instance, use clear():

const provider = new MemoryProvider();

afterEach(() => {
    provider.clear(); // wipes all tables and migration history
});

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Differences from Real Providers

Aspect	Memory Provider	Real Providers
Persistence	None — data is lost on process exit	Durable
Transactions	Not supported	Provider-dependent
SQL execution	Simulated (regex-based FROM parsing)	Native driver
Concurrency	Single-threaded	Database-managed
Performance	O(n) scans	Index-driven

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API Extensions

The MemoryProvider exposes one additional method not on IDbProvider:

/** Clears all tables and migration history. */
clear(): void;

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Requirements

• Node.js >= 18
• No external dependencies (zero-cost)

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License

MIT RomaTech / Leandro Romanelli