There never was a good war nor a bad peace.
FYI: Many native Japanese speakers actually misspell ためしがない as 試しがない. The professional proofreading team at Mainichi Newspaper explains why the Kanji 試し is incorrect. 試す in Kanji means “to try” or “to check it out”. ～のためしがない means “there is no such a precedent you may want to refer to”. A precedent should be 例 or 先例. So, the correct Kanji is 例がない and we pronounce it ためしがない.
But the pronunciation ためし for 例 is categorized as 常用漢字の表外読み（じょうようかんじのひょうがいよみ）. 常用漢字 means “a group of standardized common Kanji”. And 表外読み means “unusual pronunciations listed off from the standardized official chart by the Ministry of Education”.
You can check out other examples of 表外読み here.