Function test_adjacency_for_changed_paths 

pub fn test_adjacency_for_changed_paths(
    graph: &RetainedModuleGraph,
    root: &Path,
    changed_files: &FxHashSet<PathBuf>,
    is_test_path: &dyn Fn(&str) -> bool,
) -> Option<FxHashMap<String, TestAdjacency>>

Compute per-changed-file test adjacency for the review direction: whether a test file imports the changed module directly, and whether one of those tests is itself in the changed set. is_test_path classifies a root-relative, forward-slashed path; the caller owns that definition so the brief’s weakening and direction surfaces agree on it. Changed test files get no entry of their own. None when no module matches a changed path.