Restore missing TrySingle tests

Tests/SuperLinq.Tests/TrySingleTest.cs

@@ -13,9 +13,8 @@ public void TrySingleWithEmptySource(IDisposableEnumerable<int?> seq)
 	{
 		using (seq)
 		{
-			var (cardinality, value) = seq.TrySingle("zero", "one", "many");
+			var value = seq.TrySingle();
 
-			Assert.Equal("zero", cardinality);
 			Assert.Null(value);
 		}
 	}
@@ -26,9 +25,8 @@ public void TrySingleWithSingleton(IDisposableEnumerable<int?> seq)
 	{
 		using (seq)
 		{
-			var (cardinality, value) = seq.TrySingle("zero", "one", "many");
+			var value = seq.TrySingle();
 
-			Assert.Equal("one", cardinality);
 			Assert.Equal(1, value);
 		}
 	}
@@ -37,37 +35,62 @@ public void TrySingleWithSingleton(IDisposableEnumerable<int?> seq)
 	public void TrySingleWithSingletonCollection()
 	{
 		var source = new BreakingSingleElementCollection<int>(10);
-		var (cardinality, value) = source.TrySingle("zero", "one", "many");
+		var value = source.TrySingle();
 
-		Assert.Equal("one", cardinality);
 		Assert.Equal(10, value);
 	}
 
-	private sealed class BreakingSingleElementCollection<T>(
-		T element
-	) : ICollection<T>
+	[Test]
+	[MethodDataSource(nameof(GetAllSequences), Arguments = [2])]
+	public void TrySingleWithMoreThanOne(IDisposableEnumerable<int?> seq)
 	{
-		public int Count { get; } = 1;
+		using (seq)
+		{
+			var value = seq.TrySingle();
+
+			Assert.Null(value);
+		}
+	}
 
-		public IEnumerator<T> GetEnumerator()
+	[Test]
+	[MethodDataSource(nameof(GetAllSequences), Arguments = [0])]
+	public void TrySingleCardinalityWithEmptySource(IDisposableEnumerable<int?> seq)
+	{
+		using (seq)
 		{
-			yield return element;
-			throw new InvalidOperationException($"{nameof(SuperEnumerable.TrySingle)} should not have attempted to consume a second element.");
+			var (cardinality, value) = seq.TrySingle("zero", "one", "many");
+
+			Assert.Equal("zero", cardinality);
+			Assert.Null(value);
 		}
+	}
 
-		IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+	[Test]
+	[MethodDataSource(nameof(GetAllSequences), Arguments = [1])]
+	public void TrySingleCardinalityWithSingleton(IDisposableEnumerable<int?> seq)
+	{
+		using (seq)
+		{
+			var (cardinality, value) = seq.TrySingle("zero", "one", "many");
 
-		public void Add(T item) => throw new NotSupportedException();
-		public void Clear() => throw new NotSupportedException();
-		public bool Contains(T item) => throw new NotSupportedException();
-		public void CopyTo(T[] array, int arrayIndex) => throw new NotSupportedException();
-		public bool Remove(T item) => throw new NotSupportedException();
-		public bool IsReadOnly => true;
+			Assert.Equal("one", cardinality);
+			Assert.Equal(1, value);
+		}
+	}
+
+	[Test]
+	public void TrySingleCardinalityWithSingletonCollection()
+	{
+		var source = new BreakingSingleElementCollection<int>(10);
+		var (cardinality, value) = source.TrySingle("zero", "one", "many");
+
+		Assert.Equal("one", cardinality);
+		Assert.Equal(10, value);
 	}
 
 	[Test]
 	[MethodDataSource(nameof(GetAllSequences), Arguments = [2])]
-	public void TrySingleWithMoreThanOne(IDisposableEnumerable<int?> seq)
+	public void TrySingleCardinalityWithMoreThanOne(IDisposableEnumerable<int?> seq)
 	{
 		using (seq)
 		{
@@ -78,3 +101,25 @@ public void TrySingleWithMoreThanOne(IDisposableEnumerable<int?> seq)
 		}
 	}
 }
+
+file sealed class BreakingSingleElementCollection<T>(
+	T element
+) : ICollection<T>
+{
+	public int Count { get; } = 1;
+
+	public IEnumerator<T> GetEnumerator()
+	{
+		yield return element;
+		throw new InvalidOperationException($"{nameof(SuperEnumerable.TrySingle)} should not have attempted to consume a second element.");
+	}
+
+	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+	public void Add(T item) => throw new NotSupportedException();
+	public void Clear() => throw new NotSupportedException();
+	public bool Contains(T item) => throw new NotSupportedException();
+	public void CopyTo(T[] array, int arrayIndex) => throw new NotSupportedException();
+	public bool Remove(T item) => throw new NotSupportedException();
+	public bool IsReadOnly => true;
+}