diff --git a/src/process.rs b/src/process.rs
index 0c336b6..a6d7dfa 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -43,3 +43,45 @@ pub fn exec_result(command: &str, args: Vec<&str>) -> Result<String, ProcessErro
         Command::new(command).args(args).output()?.stdout,
     )?)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_exec_result_with_args() {
+        let result = exec_result("echo", vec!["hello", "world"]);
+
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap().trim(), "hello world");
+    }
+
+    #[test]
+    fn test_exec_success() {
+        let result = exec("echo", vec!["test"]);
+
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_exec_command_not_found() {
+        let result = exec("nonexistent_command_12345", vec![]);
+
+        assert!(result.is_err());
+
+        if let Err(ProcessError::CommandNotFound(cmd)) = result {
+            assert_eq!(cmd, "nonexistent_command_12345");
+        }
+    }
+
+    #[test]
+    fn test_exec_result_command_not_found() {
+        let result = exec_result("nonexistent_command_12345", vec![]);
+
+        assert!(result.is_err());
+
+        if let Err(ProcessError::CommandNotFound(cmd)) = result {
+            assert_eq!(cmd, "nonexistent_command_12345");
+        }
+    }
+}
diff --git a/src/sync.rs b/src/sync.rs
index 4670fcb..aaae849 100644
--- a/src/sync.rs
+++ b/src/sync.rs
@@ -5,6 +5,29 @@ use thiserror::Error;
 
 use crate::process::{exec, exec_result, ProcessError};
 
+fn parse_bundle_branches(output: &str) -> Vec<String> {
+    output
+        .split('\n')
+        .filter(|s| !s.is_empty() && s.contains("refs/heads/"))
+        .map(|s| s.split(' ').collect::<Vec<&str>>()[1].replace("refs/heads/", ""))
+        .collect()
+}
+
+fn parse_current_branches(output: &str) -> Vec<String> {
+    output
+        .split('\n')
+        .filter(|s| !s.is_empty())
+        .map(|s| s.replace(['*', ' '], ""))
+        .collect()
+}
+
+fn find_main_branch(branches: &[String]) -> &str {
+    branches
+        .iter()
+        .find(|b| *b == "develop" || *b == "master")
+        .map_or("main", |b| b)
+}
+
 #[derive(Error, Debug)]
 pub enum SyncError {
     #[error("ProcessError: {0}")]
@@ -37,22 +60,14 @@ impl Sync {
             vec!["bundle", "list-heads", &self.bundle.display().to_string()],
         )?;
 
-        self.bundle_branches = bundle_branches_str
-            .split("\n")
-            .filter(|s| !s.is_empty() && s.contains("refs/heads/"))
-            .map(|s| s.split(" ").collect::<Vec<&str>>()[1].replace("refs/heads/", ""))
-            .collect();
+        self.bundle_branches = parse_bundle_branches(&bundle_branches_str);
         Ok(())
     }
 
     fn get_current_branches(&mut self) -> Result<(), SyncError> {
         let current_branches_str = exec_result("git", vec!["branch"])?;
 
-        self.current_branches = current_branches_str
-            .split("\n")
-            .filter(|s| !s.is_empty())
-            .map(|s| s.replace("*", "").replace(" ", ""))
-            .collect();
+        self.current_branches = parse_current_branches(&current_branches_str);
         Ok(())
     }
 
@@ -65,11 +80,7 @@ impl Sync {
 
     fn checkout_to_main_branch(&self) -> Result<(), SyncError> {
         let current_branch = self.get_current_branch()?;
-        let main_branch = self
-            .current_branches
-            .iter()
-            .find(|b| *b == "develop" || *b == "master")
-            .map_or("main", |b| b);
+        let main_branch = find_main_branch(&self.current_branches);
 
         if !exec_result("git", vec!["status", "--porcelain"])?.is_empty() {
             exec("git", vec!["stash", "--include-untracked"])?;
@@ -150,3 +161,100 @@ impl Sync {
         Ok(())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_bundle_branches() {
+        let output =
+            "abc123 refs/heads/main\ndef456 refs/heads/feature-branch\nghi789 refs/heads/develop\n";
+        let branches = parse_bundle_branches(output);
+
+        assert_eq!(branches.len(), 3);
+        assert!(branches.contains(&"main".to_string()));
+        assert!(branches.contains(&"feature-branch".to_string()));
+        assert!(branches.contains(&"develop".to_string()));
+    }
+
+    #[test]
+    fn test_parse_bundle_branches_empty() {
+        let output = "";
+        let branches = parse_bundle_branches(output);
+        assert!(branches.is_empty());
+    }
+
+    #[test]
+    fn test_parse_bundle_branches_filters_non_heads() {
+        let output = "abc123 refs/tags/v1.0.0\ndef456 refs/heads/main\n";
+        let branches = parse_bundle_branches(output);
+
+        assert_eq!(branches.len(), 1);
+        assert!(branches.contains(&"main".to_string()));
+    }
+
+    #[test]
+    fn test_parse_current_branches() {
+        let output = "  feature-branch\n* main\n  develop\n";
+        let branches = parse_current_branches(output);
+
+        assert_eq!(branches.len(), 3);
+        assert!(branches.contains(&"main".to_string()));
+        assert!(branches.contains(&"feature-branch".to_string()));
+        assert!(branches.contains(&"develop".to_string()));
+    }
+
+    #[test]
+    fn test_parse_current_branches_empty() {
+        let output = "";
+        let branches = parse_current_branches(output);
+
+        assert!(branches.is_empty());
+    }
+
+    #[test]
+    fn test_find_main_branch_with_develop() {
+        let branches = vec![
+            "feature".to_string(),
+            "develop".to_string(),
+            "test".to_string(),
+        ];
+
+        assert_eq!(find_main_branch(&branches), "develop");
+    }
+
+    #[test]
+    fn test_find_main_branch_with_master() {
+        let branches = vec![
+            "feature".to_string(),
+            "master".to_string(),
+            "test".to_string(),
+        ];
+
+        assert_eq!(find_main_branch(&branches), "master");
+    }
+
+    #[test]
+    fn test_find_main_branch_fallback_to_main() {
+        let branches = vec!["feature".to_string(), "test".to_string()];
+
+        assert_eq!(find_main_branch(&branches), "main");
+    }
+
+    #[test]
+    fn test_find_main_branch_empty() {
+        let branches: Vec<String> = vec![];
+
+        assert_eq!(find_main_branch(&branches), "main");
+    }
+
+    #[test]
+    fn test_sync_new() {
+        let sync = Sync::new(PathBuf::from("/tmp/test.bundle"));
+
+        assert_eq!(sync.bundle, PathBuf::from("/tmp/test.bundle"));
+        assert!(sync.bundle_branches.is_empty());
+        assert!(sync.current_branches.is_empty());
+    }
+}