var clientMock = new Mock<DurableOrchestrationClientBase>();
var logMock = new Mock<ILogger>();
clientMock.Setup(context => context.StartNewAsync("O_SendEmail", It.IsAny<object>())).Returns(Task.FromResult(orchestrationId));

var result = await MyStarter.Run(requestMessage, this.clientMock.Object, this.logMock.Object);