In c#, async and await are turned into a state machine at compile time. My problem is hitting each piece of the state machine. I've decompiled the code and ran my exact same unit test against it to find out which branch I'm missing.
49 void IAsyncStateMachine.MoveNext()
4 50 {
4 51 int result1 = 0;
52 try
4 53 {
4 54 bool flag = true;
55 TaskAwaiter<int> awaiter;
4 56 switch (this._state)
57 {
58 case -3:
0 59 goto label_6;
60 case 0:
1 61 awaiter = this._awaiter2;
1 62 this._awaiter2 = new TaskAwaiter<int>();
1 63 this._state = -1;
1 64 break;
65 default:
3 66 awaiter = this._this._additionAsync.Add(this.value1, this.value2).GetAwaiter();
2 67 if (!awaiter.IsCompleted)
1 68 {
1 69 this._state = 0;
1 70 this._awaiter2 = awaiter;
1 71 this._builder.AwaitUnsafeOnCompleted<TaskAwaiter<int>, CalculatorAsync.d__0>(ref awaiter, ref this);
1 72 flag = false;
1 73 return;
74 }
1 75 break;
76 }
2 77 int result2 = awaiter.GetResult();
2 78 awaiter = new TaskAwaiter<int>();
2 79 this._results1 = result2;
2 80 result1 = this._results1;
2 81 }
1 82 catch (Exception ex)
1 83 {
1 84 this._state = -2;
1 85 this._builder.SetException(ex);
1 86 return;
87 }
88 label_6:
2 89 this._state = -2;
2 90 this._builder.SetResult(result1);
4 91 }
Above you can see that line 59 is hit 0 times in terms of coverage. According to this article http://www.codeproject.com/Articles/535635/Async-Await-and-the-Generated-StateMachine it's hit when the machine is requested to stop. I haven't been able cancel the async call in a manner that hits the case.
This is a test I thought would hit it but isn't.
[Test]
[ExpectedException("System.InvalidOperationException")]
public async void DecompiledCancellationTest()
{
var expectedResult = 4;
var tcs = new TaskCompletionSource<int>();
tcs.SetResult(4);
var additionHandler = new Mock<IAdditionHandler>();
additionHandler.Setup(x => x.Add(2, 2)).Returns(tcs.Task);
tcs.SetCanceled();
var calculator = new CalculatorAsync(additionHandler.Object);
var aTaskResponse = calculator.AddDecompiled(2, 2);
var aResponse = await aTaskResponse;
Assert.AreEqual(expectedResult, aResponse);
}
I've uploaded a sample to github
Using Asp.Net 4.5, Nunit 2.6.4, OpenCover 4.5.3522, and ReportGenerator 2.1.4.0
How do I get that line covered?
