Version increment for TrimExcess and EnsureCapacity (#31007)

Tests for version increment in TrimExcess and EnsureCapacity (#31007)

Revert "Version increment for TrimExcess and EnsureCapacity (#31007)"

This reverts commit 92d8f19.

Tests for enumeration invalidation in TrimExcess and EnsureCapacity (#31007)

src/System.Collections/tests/Generic/Dictionary/Dictionary.Generic.Tests.netcoreapp.cs

@@ -90,25 +90,15 @@ public void Dictionary_Generic_RemoveKey_DefaultKeyContainedInDictionary(int cou
 
         [Theory]
         [MemberData(nameof(ValidCollectionSizes))]
-        public void EnsureCapacity_Generic_RequestingLargerCapacity_DoesNotInvalidateEnumeration(int count)
+        public void EnsureCapacity_Generic_RequestingLargerCapacity_DoesInvalidateEnumeration(int count)
         {
             var dictionary = (Dictionary<TKey, TValue>)(GenericIDictionaryFactory(count));
             var capacity = dictionary.EnsureCapacity(0);
-            IEnumerator keysEnum = dictionary.Keys.GetEnumerator();
-            IEnumerator valuesEnum = dictionary.Values.GetEnumerator();
-            IEnumerator keysListEnum = new List<TKey>(dictionary.Keys).GetEnumerator();
-            IEnumerator valuesListEnum = new List<TValue>(dictionary.Values).GetEnumerator();
+            var enumerator = dictionary.GetEnumerator();
 
-            dictionary.EnsureCapacity(capacity + 1); // Verify EnsureCapacity does not invalidate enumeration
+            dictionary.EnsureCapacity(capacity + 1); // Verify EnsureCapacity does invalidate enumeration
 
-            while(keysEnum.MoveNext())
-            {
-                valuesEnum.MoveNext();
-                keysListEnum.MoveNext();
-                valuesListEnum.MoveNext();
-                Assert.Equal(keysListEnum.Current, keysEnum.Current);
-                Assert.Equal(valuesListEnum.Current, valuesEnum.Current);
-            }
+            Assert.Throws<InvalidOperationException>(() => enumerator.MoveNext());
         }
 
         [Fact]
@@ -417,6 +407,17 @@ public void TrimExcess_DictionaryHasElementsChainedWithSameHashcode_Success()
             Assert.True(dictionary.TryGetValue(chained[1], out val));
         }
 
+        [Fact]
+        public void TrimExcess_Generic_DoesInvalidateEnumeration()
+        {
+            var dictionary = new Dictionary<TKey, TValue>(20);
+            var enumerator = dictionary.GetEnumerator();
+
+            dictionary.TrimExcess(7); // Verify TrimExcess does invalidate enumeration
+
+            Assert.Throws<InvalidOperationException>(() => enumerator.MoveNext());
+        }
+
         #endregion
     }
 }