Hawzah News Agency – Imam al-Sadiq peace be upon him says:

لاتُسَمِّ الرَّجُلَ صَدِيقاً سِمَةَ مَعرِفَةٍ حتّى‏ تَختَبِرَهُ بثلاثٍ: تُغضِبُهُ فَتَنظُرُ غَضَبَهُ يُخرِجُهُ مِن الحَقِّ إلى الباطِلِ، وعندَ الدِّينارِ والدِّرهَمِ، وحتّى‏ تُسافِرَ مَعهُ.

 ‘Do not call a man your friend with the true stamp of friendship until you have tested him in three matters: anger him so that you may see whether his anger takes him away from right into wrong; test him with the dinar and the dirham [in money matters]; and travel with him.’

Source: Amali al-Tusi, p. 646, no. 1339