Added tests for 2d array

ExaArrayTests/ExaArray2DTests.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Exa;
+using NUnit.Framework;
+
+namespace ExaArrayTests
+{
+    [ExcludeFromCodeCoverage]
+    public class ExaArray2DTests
+    {
+        [Test]
+        [Category("cover")]
+        [Category("normal")]
+        public void CreatingNormalSize01()
+        {
+            var arr = new ExaArray2D<int>();
+            
+            // Empty array must have length = 0:
+            Assert.That(arr.Length, Is.EqualTo(0));
+            
+            // Try to access some points, which should return default(T):
+            Assert.That(arr[0, 0], Is.EqualTo(default(int)));
+            Assert.That(arr[1_000_000, 1_000_000], Is.EqualTo(default(int)));
+            
+            // Even after accessing some points, there should be no space allocated i.e. length is still 0:
+            Assert.That(arr.Length, Is.EqualTo(0));
+
+            // Write an int to a position:
+            arr[500, 500] = 4_756;
+            
+            // Now, we have 500 empty "rows" + 1 "row" with 501 (0-500) elements:
+            Assert.That(arr.Length, Is.EqualTo(501));
+            
+            // Should be possible to read out the value:
+            Assert.That(arr[500, 500], Is.EqualTo(4_756));
+            
+            // Change the value:
+            arr[500, 500] = 100;
+            Assert.That(arr[500, 500], Is.EqualTo(100));
+            
+            // Still the same size:
+            Assert.That(arr.Length, Is.EqualTo(501));
+            
+            // Add another value in the same "row":
+            arr[500, 499] = 499;
+            Assert.That(arr[500, 499], Is.EqualTo(499));
+            Assert.That(arr[500, 500], Is.EqualTo(100));
+            
+            // Now, we should have still 501 elements, because
+            // we added the new value "below" the previously:
+            Assert.That(arr.Length, Is.EqualTo(501));
+            
+            // Add another value in the same "row", but higher:
+            arr[500, 1_000] = 6;
+            Assert.That(arr[500, 499], Is.EqualTo(499));
+            Assert.That(arr[500, 500], Is.EqualTo(100));
+            Assert.That(arr[500, 1_000], Is.EqualTo(6));
+            
+            // Now we should have more elements:
+            Assert.That(arr.Length, Is.EqualTo(1_001));
+        }
+
+        [Test]
+        [Category("cover")]
+        [Category("normal")]
+        public void CreatingHugeSize01()
+        {
+            var arr = new ExaArray2D<int>();
+            arr[0, 1_000_000] = 47;
+            Assert.Throws<ArgumentOutOfRangeException>(() =>
+            {
+                arr[1, UInt64.MaxValue - 1] = 6;
+            });
+        }
+    }
+}