I recently have enjoyed discovering and reading various other "forgotten reformers." If you speak of the Reformation, immediately two names come up: Martin Luther and John Calvin. Yet, the Reformation was not the whim of one or two men, but the movement and culmination of many people pushing for the reform of the church such as Philip Melanchthon, Zwingli, Bullinger, Thomas Cranmer, and Martin Bucer. Bucer, in particular fascinates me. Few remember that Bucer was one of the main reformers nearly on the level with Calvin but in the German Reformed movement. He eventually ended up in England at the invite of Cranmer, before the reign of bloody Mary. Among Bucer's writings, he wrote about the necessary reforms in the church in order for the church to actually be the true church. Luther had also spoken of the signs of the church, chief among them the proper preaching of the word and the sacraments rightly administered. Bucer had another quality necessary for a true church. The Roman Church of the 1500s was not acting like the true church for this reason: it neglected the poor.
“the holy provision for the poor and needy which the Holy Spirit has prescribed and commended to us [is something that] without it there can be no true communion of saints." -Bucer
For Bucer, if you see a local body that calls itself the church, and does not care for the poor, then they are not the church, for a sign of the true church is helping the poor.