ElementAtOrDefaultAsync code coverage,

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

@@ -13,56 +13,84 @@ namespace Tests
     public class ElementAtOrDefault : AsyncEnumerableTests
     {
         [Fact]
-        public async Task ElementAtOrDefault_Null()
+        public async Task ElementAtOrDefaultAsync_Null()
         {
             await Assert.ThrowsAsync<ArgumentNullException>(() => AsyncEnumerable.ElementAtOrDefaultAsync<int>(default, 0).AsTask());
             await Assert.ThrowsAsync<ArgumentNullException>(() => AsyncEnumerable.ElementAtOrDefaultAsync<int>(default, 0, CancellationToken.None).AsTask());
         }
 
         [Fact]
-        public async Task ElementAtOrDefault1Async()
+        public async Task ElementAtOrDefaultAsync_Empty_Index0()
         {
             var res = AsyncEnumerable.Empty<int>().ElementAtOrDefaultAsync(0);
             Assert.Equal(0, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault2Async()
+        public async Task ElementAtOrDefaultAsync_Single_Index0()
         {
             var res = Return42.ElementAtOrDefaultAsync(0);
             Assert.Equal(42, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault3Async()
+        public async Task ElementAtOrDefaultAsync_Single_OutOfRange()
         {
             var res = Return42.ElementAtOrDefaultAsync(1);
             Assert.Equal(0, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault4Async()
+        public async Task ElementAtOrDefaultAsync_Single_NegativeIndex()
+        {
+            var res = Return42.ElementAtOrDefaultAsync(-1);
+            Assert.Equal(0, await res);
+        }
+
+        [Fact]
+        public async Task ElementAtOrDefaultAsync_Many_IList_InRange()
         {
             var res = new[] { 1, 42, 3 }.ToAsyncEnumerable().ElementAtOrDefaultAsync(1);
             Assert.Equal(42, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault5Async()
+        public async Task ElementAtOrDefaultAsync_Many_IList_OutOfRange()
         {
             var res = new[] { 1, 42, 3 }.ToAsyncEnumerable().ElementAtOrDefaultAsync(7);
             Assert.Equal(0, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault6Async()
+        public async Task ElementAtOrDefaultAsync_Many_IPartition_InRange()
         {
-            var res = Return42.ElementAtOrDefaultAsync(-1);
+            var res = new[] { -1, 1, 42, 3 }.ToAsyncEnumerable().Skip(1).ElementAtOrDefaultAsync(1);
+            Assert.Equal(42, await res);
+        }
+
+        [Fact]
+        public async Task ElementAtOrDefaultAsync_Many_IPartition_OutOfRange()
+        {
+            var res = new[] { -1, 1, 42, 3 }.ToAsyncEnumerable().Skip(1).ElementAtOrDefaultAsync(7);
+            Assert.Equal(0, await res);
+        }
+
+        [Fact]
+        public async Task ElementAtOrDefaultAsync_Many_InRange()
+        {
+            var res = new[] { 1, 42, 3 }.ToAsyncEnumerable().Select(x => x).ElementAtOrDefaultAsync(1);
+            Assert.Equal(42, await res);
+        }
+
+        [Fact]
+        public async Task ElementAtOrDefaultAsync_Many_OutOfRange()
+        {
+            var res = new[] { 1, 42, 3 }.ToAsyncEnumerable().Select(x => x).ElementAtOrDefaultAsync(7);
             Assert.Equal(0, await res);
         }
 
         [Fact]
-        public async Task ElementAtOrDefault7Async()
+        public async Task ElementAtOrDefaultAsync_Throws_Source()
         {
             var ex = new Exception("Bang!");
             var res = Throw<int>(ex).ElementAtOrDefaultAsync(15);