fix(assertions): address PR review for #5707

- Add Count(itemAssertion) overload for IReadOnlySet<TInner>
- Drop legacy constructor on CollectionCountEqualsAssertion (unused)
- Narrow bare catch to preserve OperationCanceledException semantics

TUnit.Assertions.Tests/Bugs/Issue5707Tests.cs

@@ -103,6 +103,20 @@ public async Task Count_Set_Items_Reach_IsSubsetOf_On_Inner()
         await Assert.That(sets).Count(s => s.IsSubsetOf(universe)).IsEqualTo(2);
     }
 
+    [Test]
+    public async Task Count_ReadOnlySet_Items_Reach_IsSubsetOf_On_Inner()
+    {
+        var universe = new HashSet<int> { 1, 2, 3, 4, 5 };
+        var sets = new List<IReadOnlySet<int>>
+        {
+            new HashSet<int> { 1, 2 },
+            new HashSet<int> { 6 },
+            new HashSet<int> { 3, 4 },
+        };
+
+        await Assert.That(sets).Count(s => s.IsSubsetOf(universe)).IsEqualTo(2);
+    }
+
     [Test]
     public async Task Count_Specialised_Source_Failure_Message_Mentions_Inner_Expectation()
     {

TUnit.Assertions/Conditions/CollectionCountSource.cs

@@ -17,8 +17,11 @@ public class CollectionCountSource<TCollection, TItem>
     public CollectionCountSource(
         AssertionContext<TCollection> collectionContext,
         Func<IAssertionSource<TItem>, Assertion<TItem>?>? assertion)
-        : this(collectionContext, WrapWithValueAssertion(assertion))
     {
+        _collectionContext = collectionContext;
+        _itemAssertionFactory = assertion is null
+            ? null
+            : (item, index) => assertion(new ValueAssertion<TItem>(item, $"item[{index}]"));
     }
 
     /// <summary>
@@ -35,17 +38,6 @@ internal CollectionCountSource(
         _itemAssertionFactory = itemAssertionFactory;
     }
 
-    internal static Func<TItem, int, IAssertion?>? WrapWithValueAssertion(
-        Func<IAssertionSource<TItem>, Assertion<TItem>?>? assertion)
-    {
-        if (assertion is null)
-        {
-            return null;
-        }
-
-        return (item, index) => assertion(new ValueAssertion<TItem>(item, $"item[{index}]"));
-    }
-
     /// <summary>
     /// Asserts that the count is equal to the expected value.
     /// Returns a collection-aware assertion that allows further collection chaining.
@@ -169,15 +161,6 @@ public class CollectionCountEqualsAssertion<TCollection, TItem> : CollectionAsse
     private readonly CountComparison _comparison;
     private int _actualCount;
 
-    internal CollectionCountEqualsAssertion(
-        AssertionContext<TCollection> context,
-        Func<IAssertionSource<TItem>, Assertion<TItem>?>? itemAssertion,
-        int expected,
-        CountComparison comparison)
-        : this(context, CollectionCountSource<TCollection, TItem>.WrapWithValueAssertion(itemAssertion), expected, comparison)
-    {
-    }
-
     internal CollectionCountEqualsAssertion(
         AssertionContext<TCollection> context,
         Func<TItem, int, IAssertion?>? itemAssertionFactory,
@@ -232,7 +215,7 @@ protected override async Task<AssertionResult> CheckAsync(EvaluationMetadata<TCo
                         await resultingAssertion.AssertAsync();
                         _actualCount++;
                     }
-                    catch
+                    catch (Exception ex) when (ex is not OperationCanceledException)
                     {
                         // Item did not satisfy the assertion, don't count it
                     }

TUnit.Assertions/Extensions/AssertionExtensions.cs

@@ -1968,6 +1968,26 @@ public static CollectionCountSource<TCollection, ISet<TInner>> Count<TCollection
             expression);
     }
 
+#if NET5_0_OR_GREATER
+    /// <summary>
+    /// Counts items satisfying an assertion expressed against an <see cref="IReadOnlySet{TInner}"/>-typed source.
+    /// Use this overload when the collection's items are themselves read-only sets; the lambda
+    /// receives a <see cref="ReadOnlySetAssertion{TInner}"/> with set-specific assertions
+    /// (IsSubsetOf, IsSupersetOf, Overlaps, etc.) in addition to the standard collection surface.
+    /// </summary>
+    public static CollectionCountSource<TCollection, IReadOnlySet<TInner>> Count<TCollection, TInner>(
+        this CollectionAssertionBase<TCollection, IReadOnlySet<TInner>> source,
+        Func<ReadOnlySetAssertion<TInner>, IAssertion?> itemAssertion,
+        [CallerArgumentExpression(nameof(itemAssertion))] string? expression = null)
+        where TCollection : IEnumerable<IReadOnlySet<TInner>>
+    {
+        return CountSpecialised<TCollection, IReadOnlySet<TInner>>(
+            source,
+            (item, index) => itemAssertion(new ReadOnlySetAssertion<TInner>(item, $"item[{index}]")),
+            expression);
+    }
+#endif
+
     private static CollectionCountSource<TCollection, TItem> CountSpecialised<TCollection, TItem>(
         CollectionAssertionBase<TCollection, TItem> source,
         Func<TItem, int, IAssertion?> itemAssertionFactory,

TUnit.PublicAPI/Tests.Assertions_Library_Has_No_API_Changes.DotNet10_0.verified.txt

@@ -2641,6 +2641,8 @@ namespace .Extensions
             where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TInner>> { }
+        public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
+            where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TKey, TValue>> Count<TCollection, TKey, TValue>(this .<TCollection, .<TKey, TValue>> source, <.<TKey, TValue>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TKey, TValue>>
             where TKey :  notnull { }

TUnit.PublicAPI/Tests.Assertions_Library_Has_No_API_Changes.DotNet8_0.verified.txt

@@ -2620,6 +2620,8 @@ namespace .Extensions
             where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TInner>> { }
+        public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
+            where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TKey, TValue>> Count<TCollection, TKey, TValue>(this .<TCollection, .<TKey, TValue>> source, <.<TKey, TValue>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TKey, TValue>>
             where TKey :  notnull { }

TUnit.PublicAPI/Tests.Assertions_Library_Has_No_API_Changes.DotNet9_0.verified.txt

@@ -2641,6 +2641,8 @@ namespace .Extensions
             where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TInner>> { }
+        public static .<TCollection, .<TInner>> Count<TCollection, TInner>(this .<TCollection, .<TInner>> source, <.<TInner>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
+            where TCollection : .<.<TInner>> { }
         public static .<TCollection, .<TKey, TValue>> Count<TCollection, TKey, TValue>(this .<TCollection, .<TKey, TValue>> source, <.<TKey, TValue>, .?> itemAssertion, [.("itemAssertion")] string? expression = null)
             where TCollection : .<.<TKey, TValue>>
             where TKey :  notnull { }