Migrate tests to XUnit

AdventOfCode2018.Tests/Day08_Tests.cs

@@ -1,28 +1,27 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Xunit;
 
 namespace AdventOfCode2018.Tests
 {
-    [TestClass]
     public class Day08_Tests
     {
-        [TestMethod]
+        [Fact]
         public void ResolvePart1__Test()
         {
             Day08 day = new Day08();
 
             string result = day.ResolvePart1(new string[] { "2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2", });
 
-            Assert.AreEqual("138", result);
+            Assert.Equal("138", result);
         }
 
-        [TestMethod]
+        [Fact]
         public void ResolvePart2__Test()
         {
             Day08 day = new Day08();
 
             string result = day.ResolvePart2(new string[] { "2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2", });
 
-            Assert.AreEqual("66", result);
+            Assert.Equal("66", result);
         }
     }
 }