Add test and fix code for (Value)Tuples with less than 2 elements. (nunit#4809)

Author: manfred-brands

src/NUnitFramework/framework/Constraints/Comparers/TupleComparerBase.cs

@@ -25,6 +25,9 @@ public static EqualMethodResult Equal(object x, object y, ref Tolerance toleranc
 
             ComparisonState comparisonState = state.PushComparison(x, y);
 
+            if (numberOfGenericArgs == 0) // Nothing to compare
+                return EqualMethodResult.ComparedEqual;
+
             uint redoWithoutTolerance = 0x0;
             for (int i = 0; i < numberOfGenericArgs; i++)
             {

src/NUnitFramework/tests/Constraints/TupleEqualityTests.cs

@@ -16,6 +16,22 @@ public void SucceedsWhenTuplesAreTheSame()
             Assert.That(tuple1, Is.EqualTo(tuple2));
         }
 
+        [Test]
+        public void SucceedsWhenTuplesAreTheSameWithinTolerance()
+        {
+            var tuple1 = Tuple.Create("Hello", 3);
+            var tuple2 = Tuple.Create("Hello", 4);
+            Assert.That(tuple1, Is.EqualTo(tuple2).Within(1));
+        }
+
+        [Test]
+        public void SucceedsWhenSingleTuplesAreTheSame()
+        {
+            var tuple1 = Tuple.Create(3);
+            var tuple2 = Tuple.Create(3);
+            Assert.That(tuple1, Is.EqualTo(tuple2));
+        }
+
         [Test]
         public void SucceedsWhenContentOfTuplesAreEquivalent()
         {

src/NUnitFramework/tests/Constraints/ValueTupleEqualityTests.cs

@@ -8,6 +8,22 @@ namespace NUnit.Framework.Tests.Constraints
     [TestFixture]
     public class ValueTupleEqualityTests
     {
+        [Test]
+        public void SucceedsWhenTuplesAreEmpty()
+        {
+            ValueTuple tuple1 = ValueTuple.Create();
+            ValueTuple tuple2 = ValueTuple.Create();
+            Assert.That(tuple1, Is.EqualTo(tuple2));
+        }
+
+        [Test]
+        public void SucceedsWhenSingleTuplesAreTheSame()
+        {
+            ValueTuple<int> tuple1 = ValueTuple.Create(3);
+            ValueTuple<int> tuple2 = ValueTuple.Create(3);
+            Assert.That(tuple1, Is.EqualTo(tuple2));
+        }
+
         [Test]
         public void SucceedsWhenTuplesAreTheSame()
         {
@@ -16,6 +32,14 @@ public void SucceedsWhenTuplesAreTheSame()
             Assert.That(tuple1, Is.EqualTo(tuple2));
         }
 
+        [Test]
+        public void SucceedsWhenTuplesAreTheSameWithinTolerance()
+        {
+            ValueTuple<string, int> tuple1 = ("Hello", 3);
+            ValueTuple<string, int> tuple2 = ("Hello", 4);
+            Assert.That(tuple1, Is.EqualTo(tuple2).Within(1));
+        }
+
         [Test]
         public void SucceedsWhenContentOfTuplesAreEquivalent()
         {