diff --git a/src/process.rs b/src/process.rs
index 443ffd8..e27f0a5 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -10,6 +10,7 @@ use std::ffi::OsStr;
 use tokio::process::Command;
 use tracing::warn;
 
+#[cfg(not(test))]
 pub async fn script_exit_code(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<i32> {
     // Run given script and return the exit code
     let mut child = Command::new(executable).args(args).spawn()?;
@@ -17,6 +18,14 @@ pub async fn script_exit_code(executable: &str, args: &[impl AsRef<OsStr>]) -> R
     status.code().ok_or(anyhow!("Killed by signal"))
 }
 
+#[cfg(test)]
+pub async fn script_exit_code(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<i32> {
+    let test = crate::testing::current();
+    let args: Vec<&OsStr> = args.iter().map(|arg| arg.as_ref()).collect();
+    let cb = &test.process_cb;
+    cb(executable, args.as_ref()).map(|(res, _)| res)
+}
+
 pub async fn run_script(name: &str, executable: &str, args: &[impl AsRef<OsStr>]) -> Result<()> {
     // Run given script to get exit code and return true on success.
     // Return Err on failure, but also print an error if needed
@@ -33,6 +42,7 @@ pub async fn run_script(name: &str, executable: &str, args: &[impl AsRef<OsStr>]
     }
 }
 
+#[cfg(not(test))]
 pub async fn script_output(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<String> {
     // Run given command and return the output given
     let output = Command::new(executable).args(args).output();
@@ -42,3 +52,11 @@ pub async fn script_output(executable: &str, args: &[impl AsRef<OsStr>]) -> Resu
     let s = std::str::from_utf8(&output.stdout)?;
     Ok(s.to_string())
 }
+
+#[cfg(test)]
+pub async fn script_output(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<String> {
+    let test = crate::testing::current();
+    let args: Vec<&OsStr> = args.iter().map(|arg| arg.as_ref()).collect();
+    let cb = &test.process_cb;
+    cb(executable, args.as_ref()).map(|(_, res)| res)
+}
diff --git a/src/testing.rs b/src/testing.rs
index 0276d09..042434d 100644
--- a/src/testing.rs
+++ b/src/testing.rs
@@ -1,4 +1,6 @@
+use anyhow::{anyhow, Result};
 use std::cell::RefCell;
+use std::ffi::OsStr;
 use std::path::Path;
 use std::rc::Rc;
 use tempfile::{tempdir, TempDir};
@@ -12,6 +14,7 @@ pub fn start() -> TestHandle {
         assert!(lock.borrow().as_ref().is_none());
         let test: Rc<Test> = Rc::new(Test {
             base: tempdir().expect("Couldn't create test directory"),
+            process_cb: |_, _| Err(anyhow!("No current process_cb")),
         });
         *lock.borrow_mut() = Some(test.clone());
         TestHandle { test }
@@ -28,6 +31,7 @@ pub fn current() -> Rc<Test> {
 
 pub struct Test {
     base: TempDir,
+    pub process_cb: fn(&str, &[&OsStr]) -> Result<(i32, String)>,
 }
 
 pub struct TestHandle {