diff --git a/src/lib.rs b/src/lib.rs
index 6b81f31..dcdf487 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -251,8 +251,8 @@ pub fn run(command: &mut Command) -> CmdOutput {
 /// ```
 pub fn run_funcs(
     command: &mut Command,
-    stdout_func: impl FnOnce(Lines<BufReader<ChildStdout>>) -> () + std::marker::Send + 'static,
-    stderr_func: impl FnOnce(Lines<BufReader<ChildStderr>>) -> () + std::marker::Send + 'static,
+    stdout_func: impl Fn(Lines<BufReader<ChildStdout>>) -> () + std::marker::Send + 'static,
+    stderr_func: impl Fn(Lines<BufReader<ChildStderr>>) -> () + std::marker::Send + 'static,
 ) -> CmdOutput {
     // https://stackoverflow.com/a/72831067/16432246
     let start = Instant::now();
@@ -330,8 +330,8 @@ pub fn run_funcs(
 /// ```
 pub fn run_funcs_with_lines(
     command: &mut Command,
-    stdout_func: impl FnOnce(Lines<BufReader<ChildStdout>>) -> Vec<Line> + std::marker::Send + 'static,
-    stderr_func: impl FnOnce(Lines<BufReader<ChildStderr>>) -> Vec<Line> + std::marker::Send + 'static,
+    stdout_func: impl Fn(Lines<BufReader<ChildStdout>>) -> Vec<Line> + std::marker::Send + 'static,
+    stderr_func: impl Fn(Lines<BufReader<ChildStderr>>) -> Vec<Line> + std::marker::Send + 'static,
 ) -> CmdOutput {
     // https://stackoverflow.com/a/72831067/16432246
     let start = Instant::now();
diff --git a/src/tests.rs b/src/tests.rs
index c4acb7d..fc209ec 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -1,13 +1,12 @@
 #[cfg(test)]
 use crate::*;
-use std::io::Write;
-use std::os::unix::fs::FileExt;
 use std::process::Command;
 use std::{
     fs::remove_file,
     hash::{BuildHasher, Hasher, RandomState},
 };
 use std::{fs::File, thread::sleep};
+use std::os::unix::fs::FileExt;
 
 /// Tests what stdout prints
 #[test]
@@ -89,8 +88,6 @@ fn shuffle_vec<T>(vec: &mut [T]) {
 
 #[test]
 fn test_run_funcs() {
-    // TODO: Add error handling to delete the file on exit
-    File::create_new("./tmp-run_funcs").unwrap();
     let threads = thread::spawn(|| {
         return run_funcs(
             Command::new("bash")
@@ -100,12 +97,11 @@ fn test_run_funcs() {
                 |stdout_lines| {
                     sleep(Duration::from_secs(1));
                     for _ in stdout_lines {
-                        let mut f = File::options()
-                            .write(true)
-                            .open("./tmp-run_funcs")
+                        Command::new("bash")
+                            .arg("-c")
+                            .arg("echo stdout >> ./tmp-run_funcs") // col
+                            .output()
                             .unwrap();
-                        f.write_all(b"stdout\n").unwrap();
-                        drop(f);
                     }
                 }
             },
@@ -113,12 +109,11 @@ fn test_run_funcs() {
                 |stderr_lines| {
                     sleep(Duration::from_secs(3));
                     for _ in stderr_lines {
-                        let f = File::options()
-                            .write(true)
-                            .open("./tmp-run_funcs")
+                        Command::new("bash")
+                            .arg("-c")
+                            .arg("echo stderr >> ./tmp-run_funcs") // col
+                            .output()
                             .unwrap();
-                        f.write_at(b"stderr\n", 7).unwrap();
-                        drop(f);
                     }
                 }
             },
@@ -145,8 +140,6 @@ fn test_run_funcs() {
 
 #[test]
 fn test_run_funcs_with_lines() {
-    // TODO: Add error handling to delete the file on exit
-    File::create_new("./tmp-run_funcs_with_lines").unwrap();
     let threads = thread::spawn(|| {
         return run_funcs_with_lines(
             &mut Command::new("bash")
@@ -160,12 +153,11 @@ fn test_run_funcs_with_lines() {
                         let line = line.unwrap();
                         lines.push(Line::from_stdout(&line));
                         assert_eq!(&line, "hi");
-                        let mut f = File::options()
-                            .write(true)
-                            .open("./tmp-run_funcs_with_lines")
+                        Command::new("bash")
+                            .arg("-c")
+                            .arg("echo stdout >> ./tmp-run_funcs_with_lines")
+                            .output()
                             .unwrap();
-                        f.write_all(b"stdout\n").unwrap();
-                        drop(f);
                     }
                     return lines;
                 }
@@ -178,13 +170,11 @@ fn test_run_funcs_with_lines() {
                         let line = line.unwrap();
                         lines.push(Line::from_stdout(&line));
                         assert_eq!(line, "hello");
-                        let mut f = File::options()
-                            .write(true)
-                            .append(true)
-                            .open("./tmp-run_funcs_with_lines")
-                            .unwrap();
-                        f.write(b"stderr\n").unwrap();
-                        drop(f);
+                        Command::new("bash")
+                            .arg("-c")
+                            .arg("echo stderr >> ./tmp-run_funcs_with_lines")
+                            .output()
+                            .unwrap(); // oops sorry lol
                     }
                     return lines;
                 }
@@ -192,13 +182,17 @@ fn test_run_funcs_with_lines() {
         );
     });
     sleep(Duration::from_secs(2));
-    let read = std::fs::read_to_string("tmp-run_funcs_with_lines").unwrap();
-    assert_eq!(read, "stdout\n");
+    let f = File::open("./tmp-run_funcs_with_lines").unwrap();
+    let mut buf: [u8; 14] = [0u8; 14];
+    f.read_at(&mut buf, 0).unwrap();
+    assert_eq!(buf, [115, 116, 100, 111, 117, 116, 10, 0, 0, 0, 0, 0, 0, 0]);
 
     sleep(Duration::from_secs(2));
-    let read = std::fs::read_to_string("tmp-run_funcs_with_lines").unwrap();
-    assert_eq!(read, "stdout\nstderr\n");
-
+    f.read_at(&mut buf, 0).unwrap();
+    assert_eq!(
+        buf,
+        [115, 116, 100, 111, 117, 116, 10, 115, 116, 100, 101, 114, 114, 10]
+    );
 
     remove_file("./tmp-run_funcs_with_lines").unwrap();