This is a very minor “bug,” but many of the Test of Strength challenges for four civilizations’ masteries are incorrectly displayed as “mastery_[civ name]_#”.
For example, the Test of Strength challenges for China read as follows:
mastery_chinese_03
mastery_chinese_07
mastery_chinese_11
mastery_chinese_15
For Ottomans and Mongols, it is only the first Test of Strength challenge that is incorrectly displayed (e.g., mastery_mongol_03). For China and Abbasid, it is ALL of the Test of Strength challenges that are displayed in this way.
Finally, the Test of Strength I challenges for Ottomans and Mongols completely lack a description of what one must do to complete them. All of the other incorrectly displayed Test of Strength challenges have a description.
The bug/labeling error might not be a top priority, but I wanted to make sure that the developers knew about it sooner rather than later, since civ masteries are not something that one might necessarily think to check.