I suggest this should do the trick:

import * as mongoose from "@typegoose/typegoose";
import { getModelForClass } from "@typegoose/typegoose";
...
const typegoose = mongoose.mongoose;
...
describe("MembershipService", () => {
  beforeAll(async () => {
    if (!process.env.MONGODB_URL_TEST) {
      throw new Error("MONGODB_URL_TEST is not set");
    }
    const uniqueUri = `${process.env.MONGODB_URL_TEST}-MembershipService`;

    await typegoose.connect(uniqueUri, {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    });
    console.log("MembershipService start", typegoose.connection.name);
    ...
    MemberModel = getModelForClass(MembershipMember);
  });

  afterAll(async () => {
    console.log("MembershipService end", typegoose.connection.name);
    await typegoose.connection.close();
    await typegoose.disconnect();
  });
});