Unit tests for ipairs and pairs, as well as changing how they handle null. ipairs now breaks at first nil value, pairs skips it

Upsilon/BaseTypes/ScriptIterator.cs

@@ -46,10 +46,10 @@ namespace Upsilon.BaseTypes
                 while (baseEnumerator.MoveNext())
                 {
                     var key = baseEnumerator.Current;
-                    if (key == null)
+                    if (key.Type == Type.Nil)
                         break;
                     var value = BaseIterator.GetValueFromIndex(key);
-                    if (value == null)
+                    if (value.Type == Type.Nil)
                         break;
                     yield return new SimpleScriptTable(new List<ScriptType>(){key, value});
                 }
@@ -71,7 +71,8 @@ namespace Upsilon.BaseTypes
                 {
                     var key = baseEnumerator.Current;
                     var value = BaseIterator.GetValueFromIndex(key);
-                    yield return new SimpleScriptTable(new List<ScriptType>(){key, value});
+                    if (value.Type != Type.Nil)
+                        yield return new SimpleScriptTable(new List<ScriptType>(){key, value});
                 }
             }
         }

UpsilonTests/StandardLibraryTests/BasicFunctionsTests.cs

@@ -29,7 +29,7 @@ namespace UpsilonTests.StandardLibraryTests
         public void IPairsTest()
         {
             const string input = @"
-arr = {100, 56, 28}
+arr = {100, 56, 28, nil, 100}
 value = 0
 for key, val in ipairs(arr) do
     value = value + val
@@ -56,5 +56,22 @@ return tonumber(""100"")
             Assert.Equal(100, result);
         }
 
+        [Fact]
+        public void PairsTest()
+        {
+            const string input = @"
+arr = {100, 56, 28, nil, 100}
+value = 0
+for key, val in pairs(arr) do
+    value = value + val
+end
+return value
+";
+            var script = new Script(input, BoundScope, StaticScope);
+            Assert.Empty(script.Diagnostics.Messages);
+            var result = script.Evaluate<long>();
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal(284, result);
+        }
     }
 }