RelationNotFound [Error]: relation "pg_enum" does not exist while using pg-mem

Question

I'm trying to test the repository layer of my TypeScript project using Jest. My approach is to create an in-memory Postgres DB and use it for test purpose. So I've chosen pg-mem. It does not implement any existing postgres extension and most of the functions. But it has options to mock them. I've used sequelize-typescript for DB models as ORM.

Some of my DB models contains enums. And postgres manages the enums using the pg_enum system catalog. But when I'm trying to run sequelize.sync({ force: true }), it is failing in a specific query and complaining RelationNotFound [Error]: relation "pg_enum" does not exist.

The failing query:

select
    t.typname enum_name,
    array_agg(e.enumlabel order by enumsortorder) enum_value
from
    pg_type t
join pg_enum e on
    t.oid = e.enumtypid
join pg_catalog.pg_namespace n on
    n.oid = t.typnamespace
where
    n.nspname = 'public'
    and t.typname = 'enum_assets_status'
group by
    1;

NB: I'm reusing the existing model declaration for test cases also (created using sequelize-typescript).

How I set it up:

import { DataType, newDb } from "pg-mem";
import { Sequelize } from "sequelize-typescript";

import { modelA, modelB } from "../../database/models";

describe("test", () => {
    const db = newDb();

    const sequelize = new Sequelize({
        dialect: "postgres",
        dialectModule: db.adapters.createPg(),
        models: [
          modelA,
          modelB
        ]
    });

    sequelize.sync({ force: true });

    //////////// Test Cases //////////////
    //////////////////////////////////////
    //////////////////////////////////////
});

What I've already tried:

As it seems pg_enum table does not exists, I tried to create one to see if it helps in some way. Reference: this comment. (Seems I've got it wrong!!)

db.registerLanguage("plpgsql", ({ code, args, returns }) => {
        return () => {
            db.public.none(`CREATE TABLE pg_enum (
                oid OID,
                enumtypid OID,
                enumsortorder NUMBER,
                enumlabel TEXT
            )`);
            db.public.none(`INSERT INTO pg_enum ("oid",enumtypid,enumsortorder,enumlabel) VALUES
                (29188,29184,2.0,'INCOMPLETE');`);
        };
    });

I've found a similar issue. How can I try this in a pg_enum context knowing that pg_enum table holds oid, enumtypid, enumsortorder and enumlabel column? Reference: this link

Or is there any other approach I can follow?

Thanks!