How to use the @loopback/openapi-v3.getControllerSpec function in @loopback/openapi-v3

it('does not fail if some of the parameters are not decorated', () => {
    class TestController {
      @get('/greet')
      greet(prefix: string, @param.query.string('message') message: string) {
        return prefix + ': ' + message;
      }
    }
    const spec = getControllerSpec(TestController);
    const table = givenRoutingTable();
    table.registerController(spec, TestController);
    const paths = table.describeApiPaths();
    const params = paths['/greet']['get'].parameters;
    expect(params).to.have.property('length', 1);
    expect(params[0]).to.have.properties({
      name: 'message',
      in: 'query',
      schema: {type: 'string'},
    });
  });