add test for day3

aoc.tests/Day3Test.cs

@@ -0,0 +1,29 @@
+using aoc2020;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace aoc.tests
+{
+    [TestClass]
+    public class Day3Test
+    {
+        private Day3 _day3;
+
+        [TestInitialize]
+        public void Initialize()
+        {
+            _day3 = new Day3();
+        }
+
+        [TestMethod]
+        public void TestPart1()
+        {
+            Assert.AreEqual("189", _day3.Part1());
+        }
+
+        [TestMethod]
+        public void TestPart2()
+        {
+            Assert.AreEqual("1718180100", _day3.Part2());
+        }
+    }
+}