feat: enhance failure messages for All assertions to include value (#4139)

Author: thomhurst

TUnit.Assertions.Tests/CollectionAssertionTests.cs

@@ -270,4 +270,40 @@ await Assert.That(names)
             .And.Contains("Bob")
             .And.DoesNotContain("Dave");
     }
+
+    [Test]
+    public async Task All_Predicate_Failure_Message_Contains_Index_And_Value()
+    {
+        var items = new[] { 2, 4, -5, 8 };
+
+        await Assert.That(async () =>
+            await Assert.That(items).All(x => x > 0)
+        ).Throws<AssertionException>()
+        .WithMessageContaining("index 2")
+        .And.WithMessageContaining("[-5]");
+    }
+
+    [Test]
+    public async Task All_Predicate_Failure_Message_Contains_String_Value()
+    {
+        var names = new[] { "Alice", "Bob", "" };
+
+        await Assert.That(async () =>
+            await Assert.That(names).All(x => !string.IsNullOrEmpty(x))
+        ).Throws<AssertionException>()
+        .WithMessageContaining("index 2")
+        .And.WithMessageContaining("[]");
+    }
+
+    [Test]
+    public async Task All_Predicate_Failure_Message_Contains_First_Failing_Item()
+    {
+        var items = new[] { 1, 2, 3, -1, -2, -3 };
+
+        await Assert.That(async () =>
+            await Assert.That(items).All(x => x > 0)
+        ).Throws<AssertionException>()
+        .WithMessageContaining("index 3")
+        .And.WithMessageContaining("[-1]");
+    }
 }

TUnit.Assertions/Conditions/CollectionAssertions.cs

@@ -423,7 +423,7 @@ protected override Task<AssertionResult> CheckAsync(EvaluationMetadata<TCollecti
         {
             if (!_predicate(item))
             {
-                return Task.FromResult(AssertionResult.Failed($"item at index {index} does not satisfy predicate"));
+                return Task.FromResult(AssertionResult.Failed($"item at index {index} with value [{item}] does not satisfy predicate"));
             }
 
             index++;