diff --git a/src/os_string_extension.rs b/src/os_string_extension.rs
index ae1e907..37a8e74 100644
--- a/src/os_string_extension.rs
+++ b/src/os_string_extension.rs
@@ -79,4 +79,45 @@ where
   }
 }
 
-//TODO unit test!
\ No newline at end of file
+#[cfg(test)]
+mod test {
+  use crate::os_string_extension::OsStrExtension;
+  use std::ffi::OsString;
+
+  #[test]
+  fn test_starts_with() {
+    assert!(OsString::from("Hello world").starts_with("Hell"));
+    assert!(!OsString::from("Hello world").starts_with("world"));
+  }
+
+  #[test]
+  fn test_ends_with() {
+    assert!(OsString::from("Hello world").ends_with("ld"));
+    assert!(!OsString::from("Hello world").ends_with("Hello"));
+  }
+
+  #[test]
+  fn test_split() {
+    assert_eq!(vec![OsString::from("Hello"), OsString::from("world")], OsString::from("Hello world").split(b' '));
+  }
+
+  #[test]
+  fn test_splitn() {
+    assert_eq!(vec![OsString::from("a"), OsString::from("b"), OsString::from("c d")], OsString::from("a b c d").splitn(3, b' '));
+  }
+
+  #[test]
+  fn test_split_once() {
+    assert_eq!(Some((OsString::from("a").as_ref(), OsString::from("b c").as_ref())), OsString::from("a b c").split_once(b' '));
+  }
+
+  #[test]
+  fn test_rsplitn() {
+    assert_eq!(vec![OsString::from("a b"), OsString::from("c"), OsString::from("d")], OsString::from("a b c d").rsplitn(3, b' '));
+  }
+
+  #[test]
+  fn test_rsplit_once() {
+    assert_eq!(Some((OsString::from("a b").as_ref(), OsString::from("c").as_ref())), OsString::from("a b c").rsplit_once(b' '));
+  }
+}