Add file path match tests

SabreTools.Matching.Test/Paths/FilePathMatchTests.cs

@@ -0,0 +1,22 @@
+using System.IO;
+using SabreTools.Matching.Paths;
+using Xunit;
+
+namespace SabreTools.Matching.Test.Paths
+{
+    /// <remarks>
+    /// All other test cases are covered by <see cref="PathMatchTests"/> 
+    /// </remarks>
+    public class FilePathMatchTests
+    {
+        [Fact]
+        public void ConstructorFormatsNeedle()
+        {
+            string needle = "test";
+            string expected = $"{Path.DirectorySeparatorChar}{needle}";
+
+            var fpm = new FilePathMatch(needle);
+            Assert.Equal(expected, fpm.Needle);
+        }
+    }
+}