public static async IAsyncEnumerable<string> GetTestValues()

{

    yield return "foo";

    yield return "bar";

​

    await Task.CompletedTask; // to make the compiler warning go away

}

​

var serviceMock = new Mock<IMyService>();

serviceMock.Setup(s => s.CallSomethingReturningAsyncStream()).Returns(GetTestValues);

​

var thing = new Thing(serviceMock.Object);

var result = await thing.MyMethodIWantToTest();

Assert.Equal("foo", result[0]);

Assert.Equal("bar", result[1]);