Remove some code duplication.

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/AsyncEnumerableExTests.cs

@@ -15,6 +15,7 @@ namespace Tests
     {
         protected static readonly IAsyncEnumerable<int> Return42 = AsyncEnumerable.Return(42);
         protected static IAsyncEnumerable<T> Throw<T>(Exception exception) => AsyncEnumerable.Throw<T>(exception);
+        protected static Func<Exception, bool> SingleInnerExceptionMatches(Exception ex) => e => ((AggregateException)e).Flatten().InnerExceptions.Single() == ex;
 
         protected const int WaitTimeoutMs = 5000;
 

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Catch.cs

@@ -112,7 +112,7 @@ namespace Tests
             HasNext(e, 2);
             HasNext(e, 3);
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
 
             Assert.False(err);
         }
@@ -133,7 +133,7 @@ namespace Tests
             HasNext(e, 2);
             HasNext(e, 3);
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex2);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex2));
         }
 
         [Fact]
@@ -160,7 +160,7 @@ namespace Tests
             HasNext(e, 2);
             HasNext(e, 3);
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -257,7 +257,7 @@ namespace Tests
             HasNext(e, 2);
             HasNext(e, 3);
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/DistinctUntilChanged.cs

@@ -70,7 +70,7 @@ namespace Tests
             HasNext(e, 1);
             HasNext(e, 2);
             HasNext(e, 3);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Do.cs

@@ -62,7 +62,7 @@ namespace Tests
             var ys = xs.Do(x => { throw ex; });
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Expand.cs

@@ -42,7 +42,7 @@ namespace Tests
             var xs = new[] { 2, 3 }.ToAsyncEnumerable().Expand(new Func<int, IAsyncEnumerable<int>>(x => { throw ex; }));
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Finally.cs

@@ -64,7 +64,7 @@ namespace Tests
             var e = xs.GetAsyncEnumerator();
 
             Assert.False(b);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
 
             Assert.True(b);
         }

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/IgnoreElements.cs

@@ -58,7 +58,7 @@ namespace Tests
             var xs = Throw<int>(ex).IgnoreElements();
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Scan.cs

@@ -52,7 +52,7 @@ namespace Tests
             var xs = new[] { 1, 2, 3 }.ToAsyncEnumerable().Scan(8, new Func<int, int, int>((x, y) => { throw ex; }));
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -62,7 +62,7 @@ namespace Tests
             var xs = new[] { 1, 2, 3 }.ToAsyncEnumerable().Scan(new Func<int, int, int>((x, y) => { throw ex; }));
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/StartWith.cs

@@ -32,12 +32,12 @@ namespace Tests
         [Fact]
         public void StartWith2()
         {
-            var xs = AsyncEnumerable.Return<int>(0).StartWith(1, 2);
+            var xs = Return42.StartWith(40, 41);
 
             var e = xs.GetAsyncEnumerator();
-            HasNext(e, 1);
-            HasNext(e, 2);
-            HasNext(e, 0);
+            HasNext(e, 40);
+            HasNext(e, 41);
+            HasNext(e, 42);
             NoNext(e);
         }
 
@@ -50,7 +50,7 @@ namespace Tests
             var e = xs.GetAsyncEnumerator();
             HasNext(e, 1);
             HasNext(e, 2);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
     }
 }

Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Using.cs

@@ -134,7 +134,7 @@ namespace Tests
             var e = xs.GetAsyncEnumerator();
             Assert.Equal(1, i);
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
 
             Assert.True(disposed.Task.Result);
         }

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/AsyncEnumerableTests.cs

@@ -15,6 +15,7 @@ namespace Tests
     {
         protected static readonly IAsyncEnumerable<int> Return42 = AsyncEnumerable.Return(42);
         protected static IAsyncEnumerable<T> Throw<T>(Exception exception) => AsyncEnumerable.Throw<T>(exception);
+        protected static Func<Exception, bool> SingleInnerExceptionMatches(Exception ex) => e => ((AggregateException)e).Flatten().InnerExceptions.Single() == ex;
 
         protected const int WaitTimeoutMs = 5000;
 

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Concat.cs

@@ -46,7 +46,7 @@ namespace Tests
             HasNext(e, 1);
             HasNext(e, 2);
             HasNext(e, 3);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -56,7 +56,7 @@ namespace Tests
             var ys = Throw<int>(ex).Concat(new[] { 4, 5, 6 }.ToAsyncEnumerable());
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -96,7 +96,7 @@ namespace Tests
             HasNext(e, 3);
             HasNext(e, 4);
             HasNext(e, 5);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/DefaultIfEmpty.cs

@@ -92,7 +92,7 @@ namespace Tests
             var xs = Throw<int>(ex).DefaultIfEmpty();
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -102,7 +102,7 @@ namespace Tests
             var xs = Throw<int>(ex).DefaultIfEmpty(24);
 
             var e = xs.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/GroupBy.cs

@@ -176,7 +176,7 @@ namespace Tests
             var ys = xs.GroupBy(x => x);
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -241,7 +241,7 @@ namespace Tests
             var ys = xs.GroupBy<int, int>(new Func<int, int>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -253,7 +253,7 @@ namespace Tests
 
             var e = ys.GetAsyncEnumerator();
 
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
 
             //Assert.True(e.MoveNext().Result);
             //var g1 = e.Current;

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/GroupJoin.cs

@@ -68,7 +68,7 @@ namespace Tests
             var res = xs.GroupJoin(ys, x => x % 3, y => y % 3, (x, i) => x + " - " + i.Aggregate("", (s, j) => s + j).Result);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -81,7 +81,7 @@ namespace Tests
             var res = xs.GroupJoin(ys, x => x % 3, y => y % 3, (x, i) => x + " - " + i.Aggregate("", (s, j) => s + j).Result);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -94,7 +94,7 @@ namespace Tests
             var res = xs.GroupJoin(ys, x => { throw ex; }, y => y % 3, (x, i) => x + " - " + i.Aggregate("", (s, j) => s + j).Result);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -107,7 +107,7 @@ namespace Tests
             var res = xs.GroupJoin(ys, x => x % 3, y => { throw ex; }, (x, i) => x + " - " + i.Aggregate("", (s, j) => s + j).Result);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -126,7 +126,7 @@ namespace Tests
 
             var e = res.GetAsyncEnumerator();
             HasNext(e, "0 - 36");
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
     }
 }

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Join.cs

@@ -97,7 +97,7 @@ namespace Tests
             var res = xs.Join(ys, x => x % 3, y => y % 3, (x, y) => x + y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -110,7 +110,7 @@ namespace Tests
             var res = xs.Join(ys, x => x % 3, y => y % 3, (x, y) => x + y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -123,7 +123,7 @@ namespace Tests
             var res = xs.Join(ys, x => { throw ex; }, y => y, (x, y) => x + y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -136,7 +136,7 @@ namespace Tests
             var res = xs.Join(ys, x => x, y => { throw ex; }, (x, y) => x + y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -149,7 +149,7 @@ namespace Tests
             var res = xs.Join<int, int, int, int>(ys, x => x, y => y, (x, y) => { throw ex; });
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/OrderBy.cs

@@ -66,7 +66,7 @@ namespace Tests
             var ys = xs.OrderBy<int, int>(new Func<int, int>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -86,7 +86,7 @@ namespace Tests
             var ys = xs.OrderBy(x => x).ThenBy<int, int>(new Func<int, int>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -109,7 +109,7 @@ namespace Tests
             var ys = xs.OrderByDescending<int, int>(new Func<int, int>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -129,7 +129,7 @@ namespace Tests
             var ys = xs.OrderBy<int, int>(x => x).ThenByDescending<int, int>(new Func<int, int>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Reverse.cs

@@ -60,7 +60,7 @@ namespace Tests
             var ys = xs.Reverse();
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/SelectMany.cs

@@ -61,7 +61,7 @@ namespace Tests
             HasNext(e, 0);
             HasNext(e, 0);
             HasNext(e, 1);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -72,7 +72,7 @@ namespace Tests
             var ys = xs.SelectMany(x => Enumerable.Range(0, x).ToAsyncEnumerable());
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -92,7 +92,7 @@ namespace Tests
             HasNext(e, 0);
             HasNext(e, 0);
             HasNext(e, 1);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -128,7 +128,7 @@ namespace Tests
             HasNext(e, 0);
             HasNext(e, 0);
             HasNext(e, 1);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -139,7 +139,7 @@ namespace Tests
             var ys = xs.SelectMany((x, i) => Enumerable.Range(0, x).ToAsyncEnumerable());
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -159,7 +159,7 @@ namespace Tests
             HasNext(e, 0);
             HasNext(e, 0);
             HasNext(e, 1);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -211,7 +211,7 @@ namespace Tests
             HasNext(e, 6);
             HasNext(e, 8);
             HasNext(e, 9);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -230,7 +230,7 @@ namespace Tests
             HasNext(e, 3);
             HasNext(e, 8);
             HasNext(e, 10);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Skip.cs

@@ -72,7 +72,7 @@ namespace Tests
             var ys = xs.Skip(2);
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/SkipWhile.cs

@@ -80,7 +80,7 @@ namespace Tests
             var ys = xs.SkipWhile(new Func<int, bool>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -127,7 +127,7 @@ namespace Tests
             var ys = xs.SkipWhile(new Func<int, int, bool>((x, i) => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Take.cs

@@ -72,7 +72,7 @@ namespace Tests
             var ys = xs.Take(2);
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/TakeWhile.cs

@@ -77,7 +77,7 @@ namespace Tests
             var ys = xs.TakeWhile(new Func<int, bool>(x => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -124,7 +124,7 @@ namespace Tests
             var ys = xs.TakeWhile(new Func<int, int, bool>((x, i) => { throw ex; }));
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
 

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Where.cs

@@ -61,7 +61,7 @@ namespace Tests
             HasNext(e, 8);
             HasNext(e, 5);
             HasNext(e, 7);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -75,7 +75,7 @@ namespace Tests
             HasNext(e, 8);
             HasNext(e, 5);
             HasNext(e, 7);
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -86,7 +86,7 @@ namespace Tests
             var ys = xs.Where(x => true);
 
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -97,7 +97,7 @@ namespace Tests
 
             var ys = xs.Where((x, i) => true);
             var e = ys.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
 

Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Zip.cs

@@ -71,7 +71,7 @@ namespace Tests
             var res = xs.Zip(ys, (x, y) => x * y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -83,7 +83,7 @@ namespace Tests
             var res = xs.Zip(ys, (x, y) => x * y);
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]
@@ -95,7 +95,7 @@ namespace Tests
             var res = xs.Zip(ys, (x, y) => { if (x > 0) throw ex; return x * y; });
 
             var e = res.GetAsyncEnumerator();
-            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), (Exception ex_) => ((AggregateException)ex_).Flatten().InnerExceptions.Single() == ex);
+            AssertThrows(() => e.MoveNextAsync().Wait(WaitTimeoutMs), SingleInnerExceptionMatches(ex));
         }
 
         [Fact]