diff --git a/Makefile b/Makefile
index caf18eea9..f03f3067e 100644
--- a/Makefile
+++ b/Makefile
@@ -42,6 +42,7 @@ TEST_PROGS  := \
   cat \
   mkdir \
   seq \
+  truncate \
 
 TEST        ?= $(TEST_PROGS)
 
diff --git a/truncate/test.rs b/truncate/test.rs
new file mode 100644
index 000000000..2562ab758
--- /dev/null
+++ b/truncate/test.rs
@@ -0,0 +1,40 @@
+use std::{run, io};
+
+static PROG: &'static str = "build/truncate";
+static TESTNAME: &'static str = "THISISARANDOMFILENAME";
+
+fn make_file() -> io::File {
+    while Path::new(TESTNAME).exists() { io::timer::sleep(1000); }
+    match io::File::create(&Path::new(TESTNAME)) {
+        Some(f) => f,
+        None => fail!()
+    }
+}
+
+#[test]
+fn test_increase_file_size() {
+    let mut file = make_file();
+    if !run::process_status(PROG, [~"-s", ~"+5K", TESTNAME.to_owned()]).unwrap().success() {
+        fail!();
+    }
+    file.seek(0, io::SeekEnd);
+    if file.tell() != 5 * 1024 {
+        fail!();
+    }
+    io::fs::unlink(&Path::new(TESTNAME));
+}
+
+#[test]
+fn test_decrease_file_size() {
+    let mut file = make_file();
+    file.write(bytes!("1234567890"));
+    if !run::process_status(PROG, [~"--size=-4", TESTNAME.to_owned()]).unwrap().success() {
+        fail!();
+    }
+    file.seek(0, io::SeekEnd);
+    if file.tell() != 6 {
+		 println!("{}", file.tell());
+        fail!();
+    }
+    io::fs::unlink(&Path::new(TESTNAME));
+}