When it comes to finding synonyms for the word "most testatory," it can be difficult to pinpoint the exact meaning. However, some viable options could include words like persuasive, convincing, affirming, corroborating, or validating. Each of these synonyms captures the idea of providing evidence or proof to support a claim or argument. Other possible alternatives could include terms like authenticating, confirming, ratifying, or substantiating. Regardless of the specific synonym chosen, the overall idea of "most testatory" is to convey a sense of reliability and trustworthiness, indicating that something is backed up by verifiable evidence or data.