public async Task Verify_CreateFlightsAsync_Invoked() { // Arrange var fileManagerMock = new Mock <IFileManager <Flight> >(); fileManagerMock.Setup(x => x.WriteToJsonAsync(It.IsAny <string>(), It.IsAny <List <Flight> >())).Verifiable(); var sut = new FlightRepository(fileManagerMock.Object); // Act await sut.CreateFlightsAsync(new List <Flight>()); // Assert Mock.Verify(); }