diff --git a/src/commands/monitor.rs b/src/commands/monitor.rs
index 71f86dd..cbe2555 100644
--- a/src/commands/monitor.rs
+++ b/src/commands/monitor.rs
@@ -142,7 +142,7 @@ pub fn execute(
     let mut pending_events = BTreeSet::new();
 
     'outer: while let Some(event) = context.monitor.get_event() {
-        if crate::timemachine::is_time_machine_running() && !context.is_timemachine_running {
+        if is_time_machine_running_logged() && !context.is_timemachine_running {
             info!("Time Machine backup started");
             context.monitor.start_timemachine_monitoring();
             context.is_timemachine_running = true;
@@ -294,6 +294,20 @@ impl Drop for Monitor {
     }
 }
 
+fn is_time_machine_running_logged() -> bool {
+    log_status(crate::timemachine::is_time_machine_running())
+}
+
+fn log_status(status: anyhow::Result<bool>) -> bool {
+    match status {
+        Ok(running) => running,
+        Err(error) => {
+            warn!("Failed to query Time Machine status: {error}");
+            false
+        }
+    }
+}
+
 mod monitor_details {
     use std::{
         collections::BTreeSet,
@@ -308,7 +322,7 @@ mod monitor_details {
     use notify::Watcher;
 
     use super::EVENT_QUEUE_SIZE;
-    use crate::{git, timemachine};
+    use crate::git;
 
     pub fn spawn_signals_thread(
         event_sender: Sender<super::Event>,
@@ -582,7 +596,7 @@ mod monitor_details {
                         TimeMachineControl::ResumeMonitoring => {
                             const TIMEOUT: Duration = Duration::from_secs(1);
                             debug!("Start monitoring tmutil status");
-                            while timemachine::is_time_machine_running() {
+                            while super::is_time_machine_running_logged() {
                                 if let Ok(TimeMachineControl::Shutdown) =
                                     control_receiver.recv_timeout(TIMEOUT)
                                 {
@@ -725,11 +739,20 @@ mod monitor_details {
 mod tests {
     use std::time::Duration;
 
+    use rstest::rstest;
     use serial_test::serial;
     use temp_dir_builder::TempDirectoryBuilder;
 
     use crate::{cache::Cache, json::save_json_file};
 
+    #[rstest]
+    #[case(Ok(true), true)]
+    #[case(Ok(false), false)]
+    #[case(Err(anyhow::anyhow!("can't determine")), false)]
+    fn test_log_status(#[case] status: anyhow::Result<bool>, #[case] expected: bool) {
+        assert_eq!(expected, super::log_status(status));
+    }
+
     /// Test the behavior in case of a missing configuration file.
     /// It should not return an error, it should create the default configuration file.
     #[test]
diff --git a/src/commands/stats.rs b/src/commands/stats.rs
index 5b68357..43ff47d 100644
--- a/src/commands/stats.rs
+++ b/src/commands/stats.rs
@@ -105,6 +105,52 @@ mod tests {
         assert_eq!(3, size);
     }
 
+    #[test]
+    fn test_execute_size_humanize() {
+        let temp_dir = TempDirectoryBuilder::default()
+            .add_text_file("a", "abc")
+            .build()
+            .unwrap();
+        let mut cache = Cache::open_in_memory().unwrap();
+        cache
+            .add_paths([temp_dir.path().join("a")].into_iter())
+            .unwrap();
+        let mut buffer = vec![];
+
+        super::execute(&cache, &mut buffer, Stats::Size { humanize: true }).unwrap();
+
+        assert_eq!("3 B", String::from_utf8(buffer).unwrap().trim());
+    }
+
+    #[test]
+    fn test_execute_size_nested_directory() {
+        let temp_dir = TempDirectoryBuilder::default()
+            .add_text_file("top/sub/deep", "xyz")
+            .add_text_file("top/shallow", "ab")
+            .build()
+            .unwrap();
+        let mut cache = Cache::open_in_memory().unwrap();
+        cache
+            .add_paths([temp_dir.path().join("top")].into_iter())
+            .unwrap();
+        let mut buffer = vec![];
+
+        super::execute(&cache, &mut buffer, Stats::Size { humanize: false }).unwrap();
+
+        let size: u64 = String::from_utf8(buffer).unwrap().trim().parse().unwrap();
+        assert_eq!(5, size);
+    }
+
+    #[test]
+    fn test_execute_last_update() {
+        let cache = Cache::open_in_memory().unwrap();
+        let mut buffer = vec![];
+
+        super::execute(&cache, &mut buffer, Stats::LastUpdate).unwrap();
+
+        assert!(!String::from_utf8(buffer).unwrap().trim().is_empty());
+    }
+
     #[test]
     fn test_fetch_total_size_does_not_follow_symlinks_outside_directory() {
         let temp_dir = TempDirectoryBuilder::default()
diff --git a/src/git.rs b/src/git.rs
index c7802f1..5724eea 100644
--- a/src/git.rs
+++ b/src/git.rs
@@ -294,6 +294,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_find_ignored_files_path_does_not_exist() {
+        assert!(
+            super::find_ignored_files(Path::new("/this/path/does/not/exist"))
+                .unwrap()
+                .is_empty()
+        );
+    }
+
     #[test]
     fn test_worktree() {
         let temp_dir = TempDirectoryBuilder::default()
diff --git a/src/main.rs b/src/main.rs
index a4c419e..6ac33fc 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -116,7 +116,7 @@ fn program(cli: Cli, redirect_log_to_console: bool) -> anyhow::Result<()> {
     import_legacy_cache_file(&cli.legacy_cache, &cli.cache)?;
     match cli.command {
         Commands::Run { dry_run, details } => {
-            check_for_ongoing_time_machine_backup(dry_run)?;
+            check_for_ongoing_time_machine_backup::<crate::timemachine::TmUtils>(dry_run)?;
 
             let mut cache = Cache::open_or_create(&cli.cache)?;
             let config = Config::load_or_create_file(&cli.config)?;
@@ -130,7 +130,7 @@ fn program(cli: Cli, redirect_log_to_console: bool) -> anyhow::Result<()> {
             commands::list::execute(&cache, &mut std::io::stdout(), separator)
         }
         Commands::Reset { dry_run, details } => {
-            check_for_ongoing_time_machine_backup(dry_run)?;
+            check_for_ongoing_time_machine_backup::<crate::timemachine::TmUtils>(dry_run)?;
 
             let mut cache = Cache::open_or_create(&cli.cache)?;
 
@@ -161,8 +161,10 @@ fn program(cli: Cli, redirect_log_to_console: bool) -> anyhow::Result<()> {
     Ok(())
 }
 
-fn check_for_ongoing_time_machine_backup(dry_run: bool) -> anyhow::Result<()> {
-    if !dry_run && crate::timemachine::is_time_machine_running() {
+fn check_for_ongoing_time_machine_backup<T: crate::timemachine::TmUtilsTrait>(
+    dry_run: bool,
+) -> anyhow::Result<()> {
+    if !dry_run && crate::timemachine::is_time_machine_running_impl::<T>()? {
         return Err(anyhow!("Time Machine is currently doing a backup."));
     }
 
@@ -276,10 +278,31 @@ mod tests {
     use temp_dir_builder::{TempDirectory, TempDirectoryBuilder};
 
     use crate::{
-        Cli, cache::Cache, config::Config, import_legacy_cache_file, import_legacy_config_file,
-        json::save_json_file, program,
+        Cli, cache::Cache, check_for_ongoing_time_machine_backup, config::Config,
+        import_legacy_cache_file, import_legacy_config_file, json::save_json_file, program,
+        timemachine::tests::{NotRunning, Running, StatusError},
     };
 
+    #[test]
+    fn test_check_for_ongoing_time_machine_backup_running() {
+        assert!(check_for_ongoing_time_machine_backup::<Running>(false).is_err());
+    }
+
+    #[test]
+    fn test_check_for_ongoing_time_machine_backup_not_running() {
+        assert!(check_for_ongoing_time_machine_backup::<NotRunning>(false).is_ok());
+    }
+
+    #[test]
+    fn test_check_for_ongoing_time_machine_backup_status_error_aborts() {
+        assert!(check_for_ongoing_time_machine_backup::<StatusError>(false).is_err());
+    }
+
+    #[test]
+    fn test_check_for_ongoing_time_machine_backup_dry_run_skips_status() {
+        assert!(check_for_ongoing_time_machine_backup::<StatusError>(true).is_ok());
+    }
+
     #[test]
     fn test_import_legacy_config_file_dont_exist() {
         import_legacy_config_file("don't exist", "don't exist").unwrap();
diff --git a/src/timemachine.rs b/src/timemachine.rs
index 39bae89..cadf435 100644
--- a/src/timemachine.rs
+++ b/src/timemachine.rs
@@ -88,20 +88,138 @@ pub fn remove_exclusions<'a>(paths: impl Iterator<Item = &'a PathBuf>) -> Vec<Er
     errors
 }
 
-pub fn is_time_machine_running() -> bool {
-    std::process::Command::new("/usr/bin/tmutil")
-        .arg("status")
-        .output()
-        .is_ok_and(|output| String::from_utf8_lossy(&output.stdout).contains("Running = 1"))
+pub(crate) trait TmUtilsTrait {
+    fn status() -> anyhow::Result<String>;
+}
+
+pub(crate) struct TmUtils;
+
+impl TmUtilsTrait for TmUtils {
+    fn status() -> anyhow::Result<String> {
+        use anyhow::Context;
+
+        let output = std::process::Command::new("/usr/bin/tmutil")
+            .arg("status")
+            .output()
+            .context("Failed to execute tmutil status")?;
+
+        status_from_output(&output)
+    }
+}
+
+fn status_from_output(output: &std::process::Output) -> anyhow::Result<String> {
+    if !output.status.success() {
+        return Err(anyhow::anyhow!(
+            "tmutil status exited with {}: {}",
+            output.status,
+            String::from_utf8_lossy(&output.stderr).trim()
+        ));
+    }
+
+    Ok(String::from_utf8_lossy(&output.stdout).into_owned())
+}
+
+pub fn is_time_machine_running() -> anyhow::Result<bool> {
+    is_time_machine_running_impl::<TmUtils>()
+}
+
+pub(crate) fn is_time_machine_running_impl<T: TmUtilsTrait>() -> anyhow::Result<bool> {
+    Ok(parse_running(&T::status()?))
+}
+
+fn parse_running(tmutil_status_stdout: &str) -> bool {
+    tmutil_status_stdout.contains("Running = 1")
 }
 
 #[cfg(test)]
 pub(crate) mod tests {
     use std::{path::Path, process::Command};
 
+    use rstest::rstest;
     use temp_dir_builder::TempDirectoryBuilder;
 
-    use crate::timemachine::{add_exclusions, remove_exclusions};
+    use crate::timemachine::{TmUtilsTrait, add_exclusions, remove_exclusions};
+
+    pub(crate) struct Running;
+    impl TmUtilsTrait for Running {
+        fn status() -> anyhow::Result<String> {
+            Ok("Backup session status:\n{\n    Running = 1;\n}".to_string())
+        }
+    }
+
+    pub(crate) struct NotRunning;
+    impl TmUtilsTrait for NotRunning {
+        fn status() -> anyhow::Result<String> {
+            Ok("Backup session status:\n{\n    Running = 0;\n}".to_string())
+        }
+    }
+
+    pub(crate) struct StatusError;
+    impl TmUtilsTrait for StatusError {
+        fn status() -> anyhow::Result<String> {
+            Err(anyhow::anyhow!("can't determine the Time Machine status"))
+        }
+    }
+
+    #[rstest]
+    #[case("Backup session status:\n{\n    Running = 1;\n}", true)]
+    #[case("Backup session status:\n{\n    Running = 0;\n}", false)]
+    #[case("", false)]
+    fn test_parse_running(#[case] stdout: &str, #[case] expected: bool) {
+        assert_eq!(expected, super::parse_running(stdout));
+    }
+
+    #[test]
+    fn test_is_time_machine_running_true() {
+        assert_eq!(
+            true,
+            super::is_time_machine_running_impl::<Running>().unwrap()
+        );
+    }
+
+    #[test]
+    fn test_is_time_machine_running_false() {
+        assert_eq!(
+            false,
+            super::is_time_machine_running_impl::<NotRunning>().unwrap()
+        );
+    }
+
+    #[test]
+    fn test_is_time_machine_running_error_propagates() {
+        assert!(super::is_time_machine_running_impl::<StatusError>().is_err());
+    }
+
+    fn exited_with(code: i32) -> std::process::ExitStatus {
+        use std::os::unix::process::ExitStatusExt;
+
+        std::process::ExitStatus::from_raw(code << 8)
+    }
+
+    #[test]
+    fn test_status_from_output_success() {
+        let output = std::process::Output {
+            status: exited_with(0),
+            stdout: b"    Running = 1;".to_vec(),
+            stderr: Vec::new(),
+        };
+
+        assert_eq!(
+            "    Running = 1;",
+            super::status_from_output(&output).unwrap()
+        );
+    }
+
+    #[test]
+    fn test_status_from_output_non_zero_exit() {
+        let output = std::process::Output {
+            status: exited_with(1),
+            stdout: Vec::new(),
+            stderr: b"boom".to_vec(),
+        };
+
+        assert!(super::status_from_output(&output).is_err());
+    }
 
     // Be careful, this test is not very reliable even if it uses the offical way (tmutil isexcluded) to
     // know if a file is excluded. For example, as soon as you add the extended attribute