diff --git a/src/commands.rs b/src/commands.rs
index 13db0b5..692be47 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -1,5 +1,7 @@
 use std::process;
 
+use mockall::mock;
+
 pub mod branch;
 pub mod delete_branches;
 pub mod fixup;
@@ -90,3 +92,158 @@ fn search_branch<T: Exec>(command: &T, branch: &str, verbose: bool) -> Result<()
         Err(()) => Err("Failed to list branch"),
     }
 }
+
+mock! {
+    pub Cmd {}
+
+    impl Exec for Cmd {
+        fn exec<'a>(&self, args: &[&'a str], verbose: bool) -> Result<String, ()>;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::commands::MockCmd;
+
+    fn cmd_branch_not_found() -> MockCmd {
+        let mut command = MockCmd::new();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["branch", "-l", "main"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Ok(String::new()));
+
+        command
+    }
+
+    fn cmd_branch_main_found() -> MockCmd {
+        let mut command = MockCmd::new();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["branch", "-l", "main"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Ok("* main".to_string()));
+
+        command
+    }
+
+    fn cmd_default_branch_master_found() -> MockCmd {
+        let mut command = cmd_branch_not_found();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["branch", "-l", "master"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Ok("* master".to_string()));
+
+        command
+    }
+
+    fn cmd_checkout_main() -> MockCmd {
+        let mut command = MockCmd::new();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["checkout", "main"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Ok(String::new()));
+
+        command
+    }
+
+    #[test]
+    fn test_get_default_branch_main() {
+        let command = cmd_branch_main_found();
+        let branch = super::get_default_branch(&command, false);
+
+        assert_eq!(branch, Ok("main"));
+    }
+
+    #[test]
+    fn test_get_default_branch_master() {
+        let command = cmd_default_branch_master_found();
+        let branch = super::get_default_branch(&command, false);
+
+        assert_eq!(branch, Ok("master"));
+    }
+
+    #[test]
+    fn test_get_base_default_to_main() {
+        let command = cmd_branch_main_found();
+        let base = super::get_base(&command, None, false);
+
+        assert_eq!(base, "main");
+    }
+
+    #[test]
+    fn test_get_base_default_to_master() {
+        let command = cmd_default_branch_master_found();
+        let base = super::get_base(&command, None, false);
+
+        assert_eq!(base, "master");
+    }
+
+    #[test]
+    fn test_get_base_supplied_base() {
+        let command = MockCmd::new();
+        let base = super::get_base(&command, Some("test".to_string()), false);
+
+        assert_eq!(base, "test");
+    }
+
+    #[test]
+    fn test_refresh_base_success() {
+        let mut command = cmd_checkout_main();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["pull"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Ok(String::new()));
+
+        let result = super::refresh_base(&command, "main", false);
+
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_refresh_base_checkout_failure() {
+        let mut command = MockCmd::new();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["checkout", "main"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Err(()));
+
+        let result = super::refresh_base(&command, "main", false);
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_refresh_base_pull_failure() {
+        let mut command = cmd_checkout_main();
+        command
+            .expect_exec()
+            .withf(|args, verbose| args == ["pull"] && !(*verbose))
+            .times(1)
+            .returning(|_, _| Err(()));
+
+        let result = super::refresh_base(&command, "main", false);
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_search_branch_found() {
+        let command = cmd_branch_main_found();
+        let result = super::search_branch(&command, "main", false);
+
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_search_branch_not_found() {
+        let command = cmd_branch_not_found();
+        let result = super::search_branch(&command, "main", false);
+
+        assert!(result.is_err());
+    }
+}
diff --git a/src/commands/branch.rs b/src/commands/branch.rs
index 2445c74..48181a4 100644
--- a/src/commands/branch.rs
+++ b/src/commands/branch.rs
@@ -2,8 +2,8 @@ use crate::commands::{refresh_base, Exec};
 
 pub fn run<T: Exec>(
     command: &T,
-    name: String,
-    base: String,
+    name: &str,
+    base: &str,
     verbose: bool,
 ) -> Result<(), &'static str> {
     let result = refresh_base(command, &base, verbose);
diff --git a/src/main.rs b/src/main.rs
index 30a0cca..62d44e4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,7 +15,7 @@ fn main() {
         Some(Commands::Branch { name, base }) => {
             let base = get_base(&command, base, cli.verbose);
 
-            branch::run(&command, name, base, cli.verbose)
+            branch::run(&command, &name, &base, cli.verbose)
         }
         Some(Commands::Rebase { base }) => {
             let base = get_base(&command, base, cli.verbose);