public void ExstsReturnsListOfPersons() { //Assert moq.Setup(m => m.Exists(It.IsAny <Person>())).Returns <Person>(p => Task.FromResult(new List <Person> { p } as IEnumerable <Person>)); long personId = 3; //Act var result = controller.Exists(new Person { Id = personId }).Result; //Assert Assert.IsInstanceOfType(result, typeof(IEnumerable <Person>)); Assert.AreEqual(personId, (result as List <Person>)?[0]?.Id); }