diff --git a/src/files/get_file_extension.test.ts b/src/files/get_file_extension.test.ts
index 822e412..d4f347c 100644
--- a/src/files/get_file_extension.test.ts
+++ b/src/files/get_file_extension.test.ts
@@ -5,21 +5,39 @@ Deno.test(
     'Get the file extension from a specific path.',
     async (test) => {
         await test.step({
-            name: 'txt',
+            name: 'Simple path with extension: txt',
             fn: () => {
-                assertEquals(getFileExtension('path/to/file.txt'), 'txt');
+                assertEquals(
+                    getFileExtension('path/to/file.txt'),
+                    'txt'
+                );
             }
         });
         await test.step({
-            name: 'tar.gz (gz)',
+            name: 'Simple path with extension: tar.gz (gz)',
             fn: () => {
-                assertEquals(getFileExtension('path/to/file.tar.gz'), 'gz');
+                assertEquals(
+                    getFileExtension('path/to/file.tar.gz'),
+                    'gz'
+                );
             }
         });
         await test.step({
-            name: 'tar.gz (gz)',
+            name: 'Complex path with special characters and extension: tar.gz (gz)',
             fn: () => {
-                assertEquals(getFileExtension('pa-th/t.o/file/wi.th/char$acte4rs.gz'), 'gz');
+                assertEquals(
+                    getFileExtension('pa-th/t.o/file/wi.th/char$acte4rs.gz'),
+                    'gz'
+                );
+            }
+        });
+        await test.step({
+            name: 'Path without file extension.',
+            fn: () => {
+                assertEquals(
+                    getFileExtension('path/without/file/'),
+                    undefined
+                );
             }
         });
     }
diff --git a/src/files/get_file_extension.ts b/src/files/get_file_extension.ts
index 52e7921..1a1a205 100644
--- a/src/files/get_file_extension.ts
+++ b/src/files/get_file_extension.ts
@@ -1,8 +1,9 @@
 /**
  * This function takes in a path to a file and returns the file extension (without the `.`).
+ * 
  * @param path The path to the file
- * @returns The file extension
+ * @returns The file extension or undefined if no file extension was found
  */
-export function getFileExtension(path : string) : string {
+export function getFileExtension(path : string) : string | undefined {
     return path.replace(/.+\.([^/.]+$)/, (_, extension) => extension);
 }
diff --git a/src/mime_types/get_mime_type.test.ts b/src/mime_types/get_mime_type.test.ts
index c903994..ae30cef 100644
--- a/src/mime_types/get_mime_type.test.ts
+++ b/src/mime_types/get_mime_type.test.ts
@@ -5,7 +5,7 @@ Deno.test(
     'Get MIME type for specific file extension.',
     async (test) => {
         const defaultMIMETypes = {
-            default: 'text/html',
+            default: 'text/plain',
             types: {
                 'text/html': [
                     'html'