public async Task GetVirtualMachinesAsync_ExpectedResult() { IUKFastECloudClient client = Substitute.For <IUKFastECloudClient>(); client.GetAllAsync(Arg.Any <UKFastClient.GetPaginatedAsyncFunc <VirtualMachine> >(), null).Returns(Task.Run <IList <VirtualMachine> >(() => { return(new List <VirtualMachine>() { new VirtualMachine(), new VirtualMachine() }); })); var ops = new VirtualMachineOperations <VirtualMachine>(client); var vms = await ops.GetVirtualMachinesAsync(); Assert.AreEqual(2, vms.Count); }