Imran bin Husayn (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "The best era of my Ummah is my era, in which I was sent, then the one after them, then the one after them. Then a people will come who will make vows and not fulfil them, who will betray and not be trustworthy, who will testify without being asked to testify, and obesity will become widespread among them." This is how all of Hisham's students narrate it, without mention of swearing; if Mu'adh preserved it, the mention of swearing in it agrees with (the hadith of) Ibn Mas'ud (may Allah be pleased with him). It is possible that what is meant regarding testimony is that he testifies to something he did not witness and does not know, so he becomes a false witness.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20600