How to Mock Objection Models

PersonService.test.ts

// https://github.com/Vincit/objection.js/issues/1477

import { Model, QueryBuilder } from "objection";

class Person extends Model {
  static get tableName() {
    return "persons";
  }

  id!: number;
  name!: string;
}

const PersonService = {
  findByName: async (name: string) => {
    return await Person.query().where({ name }).first();
  },
  getAll: async () => {
    return await Person.query();
  },
};

const mockPeople = [
  { id: 1, name: "Alice" },
  { id: 2, name: "Bob" },
];

beforeAll(async () => {
  jest.spyOn(Person, "query").mockImplementation(() => {
    return QueryBuilder.forClass(Person).resolve(mockPeople);
  });
});

describe("PersonService", () => {
  it("Can find person by name", async () => {
    const name = "Alice";
    const person = await PersonService.findByName(name);
    expect(person?.name).toBe(name);
  });

  it("Can get all people", async () => {
    const people = await PersonService.getAll();
    expect(people).toBe(mockPeople);
  });
});