test: add pet-homebrew locator coverage (#394)

Adds focused `pet-homebrew` unit tests as a small follow-up slice from
the broader coverage plan.

- Cover Homebrew locator metadata and Linuxbrew identification
- Cover non-Homebrew, virtualenv, and Conda rejection paths
- Cover Homebrew path classification and `HOMEBREW_PREFIX` bin discovery
- Keep this PR scoped to `pet-homebrew` only

Fixes #393
Part of #389

Author: karthiknadig

Cargo.lock

@@ -19,3 +19,6 @@ pet-core = { path = "../pet-core" }
 log = "0.4.21"
 regex = "1.10.4"
 rayon = "1.11.0"
+
+[dev-dependencies]
+tempfile = "3.10"

crates/pet-homebrew/Cargo.toml

@@ -48,3 +48,47 @@ pub fn get_homebrew_prefix_bin(env_vars: &EnvVariables) -> Vec<PathBuf> {
 
     homebrew_prefixes
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use tempfile::tempdir;
+
+    #[test]
+    fn homebrew_prefix_bin_uses_existing_homebrew_prefix_env_var() {
+        let homebrew_prefix = tempdir().unwrap();
+        let homebrew_bin = homebrew_prefix.path().join("bin");
+        fs::create_dir_all(&homebrew_bin).unwrap();
+        let env_vars = EnvVariables {
+            home: None,
+            root: None,
+            path: None,
+            homebrew_prefix: Some(homebrew_prefix.path().to_string_lossy().to_string()),
+            known_global_search_locations: vec![],
+        };
+
+        let prefix_bins = get_homebrew_prefix_bin(&env_vars);
+
+        assert!(prefix_bins.contains(&homebrew_bin));
+    }
+
+    #[test]
+    fn homebrew_prefix_bin_ignores_missing_homebrew_prefix_env_var() {
+        let homebrew_prefix_parent = tempdir().unwrap();
+        let missing_homebrew_prefix = homebrew_prefix_parent.path().join("missing-prefix");
+        let env_vars = EnvVariables {
+            home: None,
+            root: None,
+            path: None,
+            homebrew_prefix: Some(missing_homebrew_prefix.to_string_lossy().to_string()),
+            known_global_search_locations: vec![],
+        };
+
+        let prefix_bins = get_homebrew_prefix_bin(&env_vars);
+
+        assert!(!prefix_bins
+            .iter()
+            .any(|path| path == &missing_homebrew_prefix.join("bin")));
+    }
+}

crates/pet-homebrew/src/environment_locations.rs

@@ -170,3 +170,115 @@ impl Locator for Homebrew {
         });
     }
 }
+
+#[cfg(all(test, unix))]
+mod tests {
+    use super::*;
+    use tempfile::tempdir;
+
+    struct TestEnvironment {
+        homebrew_prefix: Option<String>,
+    }
+
+    impl Environment for TestEnvironment {
+        fn get_user_home(&self) -> Option<PathBuf> {
+            None
+        }
+
+        fn get_root(&self) -> Option<PathBuf> {
+            None
+        }
+
+        fn get_env_var(&self, key: String) -> Option<String> {
+            if key == "HOMEBREW_PREFIX" {
+                self.homebrew_prefix.clone()
+            } else {
+                None
+            }
+        }
+
+        fn get_know_global_search_locations(&self) -> Vec<PathBuf> {
+            vec![]
+        }
+    }
+
+    #[test]
+    fn homebrew_locator_reports_kind_and_supported_category() {
+        let locator = Homebrew::from(&TestEnvironment {
+            homebrew_prefix: None,
+        });
+
+        assert_eq!(locator.get_kind(), LocatorKind::Homebrew);
+        assert_eq!(
+            locator.supported_categories(),
+            vec![PythonEnvironmentKind::Homebrew]
+        );
+    }
+
+    #[test]
+    fn try_from_identifies_linuxbrew_python_executable() {
+        let locator = Homebrew::from(&TestEnvironment {
+            homebrew_prefix: None,
+        });
+        let env = PythonEnv::new(
+            PathBuf::from("/home/linuxbrew/.linuxbrew/Cellar/python@3.12/3.12.4/bin/python3.12"),
+            None,
+            None,
+        );
+
+        let homebrew_env = locator.try_from(&env).unwrap();
+
+        assert_eq!(homebrew_env.kind, Some(PythonEnvironmentKind::Homebrew));
+        assert_eq!(
+            homebrew_env.executable,
+            Some(PathBuf::from("/home/linuxbrew/.linuxbrew/bin/python3.12"))
+        );
+        assert_eq!(homebrew_env.version, Some("3.12.4".to_string()));
+        assert_eq!(homebrew_env.prefix, None);
+        assert!(homebrew_env
+            .symlinks
+            .as_ref()
+            .unwrap()
+            .contains(&PathBuf::from(
+                "/home/linuxbrew/.linuxbrew/Cellar/python@3.12/3.12.4/bin/python3.12"
+            )));
+    }
+
+    #[test]
+    fn try_from_rejects_non_homebrew_python() {
+        let locator = Homebrew::from(&TestEnvironment {
+            homebrew_prefix: None,
+        });
+        let env = PythonEnv::new(PathBuf::from("/usr/bin/python3.12"), None, None);
+
+        assert!(locator.try_from(&env).is_none());
+    }
+
+    #[test]
+    fn try_from_rejects_virtualenv_and_conda_prefixes() {
+        let locator = Homebrew::from(&TestEnvironment {
+            homebrew_prefix: None,
+        });
+
+        let venv_root = tempdir().unwrap();
+        let venv_bin = venv_root.path().join("bin");
+        fs::create_dir_all(&venv_bin).unwrap();
+        fs::write(venv_bin.join("activate"), b"").unwrap();
+        let venv_executable = venv_bin.join("python3.12");
+        fs::write(&venv_executable, b"").unwrap();
+        let venv = PythonEnv::new(venv_executable, Some(venv_root.path().to_path_buf()), None);
+        assert!(locator.try_from(&venv).is_none());
+
+        let conda_root = tempdir().unwrap();
+        fs::create_dir_all(conda_root.path().join("conda-meta")).unwrap();
+        let conda_executable = conda_root.path().join("bin").join("python3.12");
+        fs::create_dir_all(conda_executable.parent().unwrap()).unwrap();
+        fs::write(&conda_executable, b"").unwrap();
+        let conda = PythonEnv::new(
+            conda_executable,
+            Some(conda_root.path().to_path_buf()),
+            None,
+        );
+        assert!(locator.try_from(&conda).is_none());
+    }
+}

crates/pet-homebrew/src/lib.rs

@@ -243,3 +243,39 @@ pub fn get_known_symlinks_impl(
         vec![]
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn homebrew_python_paths_are_recognized_across_supported_prefixes() {
+        assert!(is_homebrew_python(Path::new(
+            "/opt/homebrew/Cellar/python@3.12/3.12.4/bin/python3.12"
+        )));
+        assert!(is_homebrew_python(Path::new(
+            "/usr/local/Cellar/python@3.11/3.11.9/bin/python3.11"
+        )));
+        assert!(is_homebrew_python(Path::new(
+            "/home/linuxbrew/.linuxbrew/Cellar/python@3.12/3.12.4/bin/python3.12"
+        )));
+        assert!(!is_homebrew_python(Path::new("/usr/bin/python3.12")));
+    }
+
+    #[test]
+    fn known_symlink_templates_include_resolved_executable_for_linuxbrew() {
+        let resolved_exe =
+            PathBuf::from("/home/linuxbrew/.linuxbrew/Cellar/python@3.12/3.12.4/bin/python3.12");
+        let symlinks = get_known_symlinks_impl(&resolved_exe, &"3.12.4".to_string());
+
+        assert!(symlinks.contains(&resolved_exe));
+    }
+
+    #[test]
+    fn known_symlink_templates_return_empty_for_unrecognized_paths() {
+        assert!(
+            get_known_symlinks_impl(Path::new("/usr/bin/python3.12"), &"3.12.4".to_string())
+                .is_empty()
+        );
+    }
+}