diff --git a/TwitchDownloaderCore.Tests/ToolTests/FilenameServiceTests.cs b/TwitchDownloaderCore.Tests/ToolTests/FilenameServiceTests.cs
index 078607d8..6e346fa9 100644
--- a/TwitchDownloaderCore.Tests/ToolTests/FilenameServiceTests.cs
+++ b/TwitchDownloaderCore.Tests/ToolTests/FilenameServiceTests.cs
@@ -1,5 +1,4 @@
-using TwitchDownloaderCore.Extensions;
-using TwitchDownloaderCore.Tools;
+using TwitchDownloaderCore.Tools;
 
 namespace TwitchDownloaderCore.Tests.ToolTests
 {
@@ -148,6 +147,17 @@ public void DoesNotInterpretBogusTemplateParameter()
             Assert.Equal(EXPECTED, result);
         }
 
+        [Fact]
+        public void GetFilenameDoesNotThrow_WhenNullOrDefaultInput()
+        {
+            const string TEMPLATE = "{title}-{id}-{date}-{channel}-{trim_start}-{trim_end}-{length}-{views}-{game}-{date_custom=\"s\"}-{trim_start_custom=\"hh\\-mm\\-ss\"}-{trim_end_custom=\"hh\\-mm\\-ss\"}-{length_custom=\"hh\\-mm\\-ss\"}";
+            const string EXPECTED = "--1-1-01--00-00-00-00-00-00-00-00-00-0--0001-01-01T00_00_00-00-00-00-00-00-00-00-00-00";
+
+            var result = FilenameService.GetFilename(TEMPLATE, default, default, default, default, default, default, default, default);
+
+            Assert.Equal(EXPECTED, result);
+        }
+
         [Theory]
         [InlineData("\"", "＂")]
         [InlineData("*", "＊")]
@@ -166,6 +176,17 @@ public void CorrectlyReplacesInvalidFilenameCharacters(string str, string expect
             Assert.Equal(expected, actual);
         }
 
+        [Fact]
+        public void ReplaceInvalidFilenameCharactersDoesNotThrow_WhenNullInput()
+        {
+            const string? STR = null;
+            const string? EXPECTED = null;
+
+            var actual = FilenameService.ReplaceInvalidFilenameChars(STR);
+
+            Assert.Equal(EXPECTED, actual);
+        }
+
         [Fact]
         public void GetNonCollidingNameWorks_WhenNoCollisionExists()
         {