diff --git a/Cargo.lock b/Cargo.lock
index 8c49f670..a4665a30 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -690,6 +690,7 @@ dependencies = [
  "regex",
  "serde",
  "serde_json",
+ "tempfile",
 ]
 
 [[package]]
diff --git a/crates/pet-pyenv/Cargo.toml b/crates/pet-pyenv/Cargo.toml
index 404ee53d..f44ec5d3 100644
--- a/crates/pet-pyenv/Cargo.toml
+++ b/crates/pet-pyenv/Cargo.toml
@@ -18,3 +18,6 @@ pet-fs = { path = "../pet-fs" }
 pet-conda = { path = "../pet-conda" }
 log = "0.4.21"
 regex = "1.10.4"
+
+[dev-dependencies]
+tempfile = "3.10.1"
diff --git a/crates/pet-pyenv/src/environment_locations.rs b/crates/pet-pyenv/src/environment_locations.rs
index c395b2ae..4741395e 100644
--- a/crates/pet-pyenv/src/environment_locations.rs
+++ b/crates/pet-pyenv/src/environment_locations.rs
@@ -45,3 +45,108 @@ pub fn get_pyenv_dir(env_vars: &EnvVariables) -> Option<PathBuf> {
         None => env_vars.pyenv.as_ref().map(PathBuf::from),
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use tempfile::tempdir;
+
+    fn make_env_vars(
+        home: Option<PathBuf>,
+        pyenv_root: Option<String>,
+        pyenv: Option<String>,
+        known_paths: Vec<PathBuf>,
+    ) -> EnvVariables {
+        EnvVariables {
+            home,
+            root: None,
+            path: None,
+            pyenv_root,
+            pyenv,
+            known_global_search_locations: known_paths,
+        }
+    }
+
+    // get_pyenv_dir tests
+    #[test]
+    fn get_pyenv_dir_prefers_pyenv_root_over_pyenv() {
+        let env = make_env_vars(
+            None,
+            Some("/custom/pyenv-root".to_string()),
+            Some("/other/pyenv".to_string()),
+            vec![],
+        );
+        assert_eq!(
+            get_pyenv_dir(&env),
+            Some(PathBuf::from("/custom/pyenv-root"))
+        );
+    }
+
+    #[test]
+    fn get_pyenv_dir_falls_back_to_pyenv_env_var() {
+        let env = make_env_vars(None, None, Some("/fallback/pyenv".to_string()), vec![]);
+        assert_eq!(get_pyenv_dir(&env), Some(PathBuf::from("/fallback/pyenv")));
+    }
+
+    #[test]
+    fn get_pyenv_dir_returns_none_when_no_env_vars() {
+        let env = make_env_vars(None, None, None, vec![]);
+        assert_eq!(get_pyenv_dir(&env), None);
+    }
+
+    // get_home_pyenv_dir tests
+    #[test]
+    fn get_home_pyenv_dir_returns_none_without_home() {
+        let env = make_env_vars(None, None, None, vec![]);
+        assert_eq!(get_home_pyenv_dir(&env), None);
+    }
+
+    #[test]
+    fn get_home_pyenv_dir_returns_expected_path_with_home() {
+        let home = tempdir().unwrap();
+        let env = make_env_vars(Some(home.path().to_path_buf()), None, None, vec![]);
+        let result = get_home_pyenv_dir(&env).unwrap();
+        let path_str = result.to_string_lossy();
+        if cfg!(windows) {
+            assert!(
+                path_str.contains(".pyenv"),
+                "Expected .pyenv in path: {}",
+                path_str
+            );
+            assert!(
+                path_str.contains("pyenv-win"),
+                "Expected pyenv-win in path: {}",
+                path_str
+            );
+        } else {
+            assert!(result.ends_with(".pyenv"));
+        }
+    }
+
+    // get_binary_from_known_paths tests
+    #[test]
+    fn get_binary_from_known_paths_finds_pyenv_binary() {
+        let dir = tempdir().unwrap();
+        let bin_name = if cfg!(windows) { "pyenv.bat" } else { "pyenv" };
+        let exe = dir.path().join(bin_name);
+        fs::write(&exe, b"").unwrap();
+
+        let env = make_env_vars(None, None, None, vec![dir.path().to_path_buf()]);
+        let result = get_binary_from_known_paths(&env);
+        assert!(result.is_some());
+    }
+
+    #[test]
+    fn get_binary_from_known_paths_returns_none_when_not_found() {
+        let dir = tempdir().unwrap();
+        let env = make_env_vars(None, None, None, vec![dir.path().to_path_buf()]);
+        assert!(get_binary_from_known_paths(&env).is_none());
+    }
+
+    #[test]
+    fn get_binary_from_known_paths_returns_none_for_empty_paths() {
+        let env = make_env_vars(None, None, None, vec![]);
+        assert!(get_binary_from_known_paths(&env).is_none());
+    }
+}
diff --git a/crates/pet-pyenv/src/environments.rs b/crates/pet-pyenv/src/environments.rs
index 0f2fb51d..d20d1829 100644
--- a/crates/pet-pyenv/src/environments.rs
+++ b/crates/pet-pyenv/src/environments.rs
@@ -100,3 +100,244 @@ fn get_version(folder_name: &str) -> Option<String> {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use std::path::PathBuf;
+    use tempfile::tempdir;
+
+    // get_version tests
+    #[test]
+    fn get_version_parses_stable_version() {
+        assert_eq!(get_version("3.10.10"), Some("3.10.10".to_string()));
+        assert_eq!(get_version("3.12.0"), Some("3.12.0".to_string()));
+        assert_eq!(get_version("2.7.18"), Some("2.7.18".to_string()));
+    }
+
+    #[test]
+    fn get_version_parses_dev_version() {
+        assert_eq!(get_version("3.10-dev"), Some("3.10-dev".to_string()));
+        assert_eq!(get_version("3.13-dev"), Some("3.13-dev".to_string()));
+    }
+
+    #[test]
+    fn get_version_parses_alpha_rc_version() {
+        assert_eq!(get_version("3.10.0a3"), Some("3.10.0a3".to_string()));
+        assert_eq!(get_version("3.12.0b1"), Some("3.12.0b1".to_string()));
+    }
+
+    #[test]
+    fn get_version_returns_none_for_multi_letter_prerelease() {
+        // Known limitation: BETA_PYTHON_VERSION regex uses \w (single char) so multi-letter
+        // pre-release tags like "rc" are not captured. Real pyenv installs can have rc versions
+        // (e.g. 3.13.0rc1), but version detection falls back to header files in that case.
+        assert_eq!(get_version("3.11.0rc2"), None);
+    }
+
+    #[test]
+    fn get_version_parses_win32_version() {
+        assert_eq!(get_version("3.11.0a4-win32"), Some("3.11.0a4".to_string()));
+    }
+
+    #[test]
+    fn get_version_returns_none_for_non_version_strings() {
+        assert_eq!(get_version("mambaforge-4.10.1-4"), None);
+        assert_eq!(get_version("pypy3.9-7.3.15"), None);
+        assert_eq!(get_version("my-virtual-env"), None);
+        assert_eq!(get_version(""), None);
+    }
+
+    #[test]
+    fn get_version_returns_none_for_partial_version() {
+        assert_eq!(get_version("3.10"), None);
+    }
+
+    // get_generic_python_environment tests
+    #[test]
+    fn get_generic_python_environment_with_stable_version_folder() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("3.12.0");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let result = get_generic_python_environment(&exe, &env_path, &None).unwrap();
+
+        assert_eq!(result.kind, Some(PythonEnvironmentKind::Pyenv));
+        assert_eq!(
+            result.executable.as_ref().unwrap().file_name(),
+            exe.file_name()
+        );
+        assert_eq!(result.version, Some("3.12.0".to_string()));
+        assert_eq!(
+            result.prefix.as_ref().unwrap().file_name(),
+            env_path.file_name()
+        );
+        assert!(result.manager.is_none());
+    }
+
+    #[test]
+    fn get_generic_python_environment_with_win32_folder_sets_x86_arch() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("3.11.0a4-win32");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let result = get_generic_python_environment(&exe, &env_path, &None).unwrap();
+
+        assert_eq!(result.arch, Some(Architecture::X86));
+    }
+
+    #[test]
+    fn get_generic_python_environment_with_non_win32_folder_has_no_arch() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("3.12.0");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let result = get_generic_python_environment(&exe, &env_path, &None).unwrap();
+
+        assert!(result.arch.is_none());
+    }
+
+    #[test]
+    fn get_generic_python_environment_includes_manager_when_provided() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("3.12.0");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let mgr = EnvManager::new(
+            PathBuf::from("/usr/bin/pyenv"),
+            pet_core::manager::EnvManagerType::Pyenv,
+            Some("2.4.0".to_string()),
+        );
+        let result = get_generic_python_environment(&exe, &env_path, &Some(mgr.clone())).unwrap();
+
+        assert_eq!(result.manager, Some(mgr));
+    }
+
+    #[test]
+    fn get_generic_python_environment_with_unrecognized_folder_name() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("mambaforge-4.10.1-4");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let result = get_generic_python_environment(&exe, &env_path, &None).unwrap();
+
+        assert_eq!(result.kind, Some(PythonEnvironmentKind::Pyenv));
+        // No version extractable from folder name and no header files
+        assert!(result.version.is_none());
+    }
+
+    // get_virtual_env_environment tests
+    #[test]
+    fn get_virtual_env_returns_none_without_pyvenv_cfg() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("my-venv");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+
+        let result = get_virtual_env_environment(&exe, &env_path, &None);
+
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn get_virtual_env_returns_env_with_pyvenv_cfg() {
+        let root = tempdir().unwrap();
+        let env_path = root.path().join("my-venv");
+        let bin_dir = if cfg!(windows) {
+            env_path.join("Scripts")
+        } else {
+            env_path.join("bin")
+        };
+        fs::create_dir_all(&bin_dir).unwrap();
+        let exe = if cfg!(windows) {
+            bin_dir.join("python.exe")
+        } else {
+            bin_dir.join("python")
+        };
+        fs::write(&exe, b"").unwrap();
+        fs::write(
+            env_path.join("pyvenv.cfg"),
+            "version = 3.12.0\nhome = /usr/bin\n",
+        )
+        .unwrap();
+
+        let result = get_virtual_env_environment(&exe, &env_path, &None).unwrap();
+
+        assert_eq!(result.kind, Some(PythonEnvironmentKind::PyenvVirtualEnv));
+        assert_eq!(result.version, Some("3.12.0".to_string()));
+        assert_eq!(
+            result.executable.as_ref().unwrap().file_name(),
+            exe.file_name()
+        );
+        assert_eq!(
+            result.prefix.as_ref().unwrap().file_name(),
+            env_path.file_name()
+        );
+    }
+}