Unit Testing Async Methods

On a recent project I came across a situation where I needed to unit test a library that used RestSharp asynchronously. Here's an example of how it's done:

[Test]
public async Task GetBuildsOKTest()
{
    var builds = new BuildsDTO();
            
    var rr = new RestResponse<BuildsDTO>
    {
        StatusCode = HttpStatusCode.OK,
        Data = builds
    };
           
    var restClient = new Mock<IRestClient>();
    restClient
        .Setup(x => x.ExecuteTaskAsync<BuildsDTO>(
              It.IsAny<IRestRequest>(),
              It.IsAny<CancellationToken>()))
        .Returns(Task.FromResult(rr as IRestResponse<BuildsDTO>));
            
    var _service = new VSTSService(restClient.Object);
    var b = await _service.GetBuilds(BuildId);

    Assert.IsNotNull(b);
}