TestExample.test.ts

import {when} from 'mobx';
import {Resource} from './Resource';

describe('Resource', () => {
  it('initial value is the default value when default getter is available', () => {
    const defaultValue = 1;
    const asyncValue = 2;
    const r = new Resource('test', async () => asyncValue, () => defaultValue);
    expect(r.value).toBe(defaultValue);
  });

  it('initial value is undefined when no default getter is available', () => {
    const r = new Resource('test', async () => 5);
    expect(r.value).toBeUndefined();
  });

  it('default value is replaced by async value', async () => {
    const defaultValue = 1;
    const asyncValue = 2;
    const r = new Resource('test', async () => asyncValue, () => defaultValue);
    await when(() => r.isResolved);
    expect(r.value).toBe(asyncValue);
  });

  it('maintains value while updating', async () => {
    let value = 1;
    const r = new Resource('test', async () => value);
    await when(() => r.isResolved);
    value = 2;
    const promise = r.update();
    expect(r.value).toBe(1);
    await promise;
  });

  it('changes value after updating', async () => {
    let value = 1;
    const r = new Resource('test', async () => value);
    await when(() => r.isResolved);
    value = 2;
    await r.update();
    expect(r.value).toBe(2);
  });
});