Add filter tests, fix issues found

SabreTools.Test/Filter/FilteringTests.cs

@@ -0,0 +1,82 @@
+using SabreTools.DatItems;
+using SabreTools.DatItems.Formats;
+using SabreTools.Filter;
+using Xunit;
+
+namespace SabreTools.Test.Filter
+{
+    public class FilteringTests
+    {
+        [Fact]
+        public void PassesFiltersDatItemFilterPass()
+        {
+            // Setup filter
+            var filter = new FilterRunner(["rom.name:foo"]);
+
+            // Setup DatItem
+            var datItem = CreateDatItem();
+
+            // Run filters
+            bool actual = datItem.PassesFilter(filter);
+            Assert.True(actual);
+        }
+
+        [Fact]
+        public void PassesFiltersDatItemFilterFail()
+        {
+            // Setup filter
+            var filter = new FilterRunner(["rom.name:bar"]);
+
+            // Setup DatItem
+            var datItem = CreateDatItem();
+
+            // Run filters
+            bool actual = datItem.PassesFilter(filter);
+            Assert.False(actual);
+        }
+
+        [Fact]
+        public void PassesFiltersMachineFilterPass()
+        {
+            // Setup filter
+            var filter = new FilterRunner(["machine.name:bar"]);
+
+            // Setup DatItem
+            var datItem = CreateDatItem();
+
+            // Run filters
+            bool actual = datItem.PassesFilter(filter);
+            Assert.True(actual);
+        }
+
+        [Fact]
+        public void PassesFiltersMachineFilterFail()
+        {
+            // Setup filter
+            var filter = new FilterRunner(["machine.name:foo"]);
+
+            // Setup DatItem
+            var datItem = CreateDatItem();
+
+            // Run filters
+            bool actual = datItem.PassesFilter(filter);
+            Assert.False(actual);
+        }
+
+        /// <summary>
+        /// Generate a consistent DatItem for testing
+        /// </summary>
+        private static DatItem CreateDatItem()
+        {
+            return new Rom
+            {
+                Name = "foo",
+                Machine = new Machine
+                {
+                    Name = "bar",
+                    Description = "bar",
+                }
+            };
+        }
+    }
+}