// file: src/class.ts
export class TestClass {
  public doAThing() {
    return 12;
  }
}

// file: src/__tests__/class.test.ts
import { expect, test, vitest } from "vitest";
import { TestClass } from "../class.js";

vitest.mock("../class.js");

test("isolation", () => {
  const inst1 = new TestClass();

  // Normally, using the prototype counts the same calls as the instance.
  void inst1.doAThing();
  expect(inst1.doAThing).toHaveBeenCalledTimes(1);
  expect(TestClass.prototype.doAThing).toHaveBeenCalledTimes(1);

  // However, mocking the implementation of the instance detaches calls from the
  // prototype.
  vitest.mocked(inst1.doAThing).mockReturnValue(21);
  void inst1.doAThing();
  expect(inst1.doAThing).toHaveBeenCalledTimes(2);
  expect.soft(TestClass.prototype.doAThing).toHaveBeenCalledTimes(2);

  // Resetting mocks should restore back to the original behavior, but it doesn't:
  vitest.resetAllMocks();

  void inst1.doAThing();
  expect(inst1.doAThing).toHaveBeenCalledTimes(1);
  expect.soft(TestClass.prototype.doAThing).toHaveBeenCalledTimes(1); // This is once again decoupled.

  // And now the constructor shim is also broken, so these two instances are no longer isolated.
  const inst2 = new TestClass();
  const inst3 = new TestClass();

  expect.soft(inst2.doAThing).not.toBe(inst3.doAThing);
  expect.soft(vitest.mocked(inst2.doAThing).mock).not.toBe(vitest.mocked(inst3.doAThing).mock);

  void inst2.doAThing();
  expect(inst2.doAThing).toHaveBeenCalledTimes(1);
  expect.soft(inst3.doAThing).toHaveBeenCalledTimes(0);
});