**Textual corruption:** Compare a name or wording with reliably established forms.
**Concealed identity:** Resolve a kunyah or unusual attribution before evaluating the underlying teacher.
**Source criticism:** Examine the source’s reliability even when an act of reading or hearing is established.
**Chronological contradiction:** Reject an attribution that places a person at an event occurring after his death.
Each test has its own evidentiary scope; invalidating one chain does not automatically settle every independent route or every version of the matn.