"And Moses took the tabernacle, and pitched it without the camp, afar off from the camp, and called it the Tabernacle of the congregation. And it came to pass, that every one which sought the LORD went out unto the tabernacle of the congregation, which was without the camp. Exod. 33: 7.
When the camp of Israel was defiled by a golden calf, separation from evil became all who sought the Lord, for He and evil cannot go on together. Moses acted with God-given perception in placing the Tabernacle "afar off" from that defiled place, and then, "every one which sought the LORD" went out to where the Lord was.
It is important to notice that each one had to act individually when he walked out from the camp to where the Lord was—in that, it was individual seeking of the Lord on the one hand and testimony against evil on the other. Another important point comes out in the fact that when the individual reached the appointed place he had two things: the Lord, and the fellowship of all his brethren who were likeminded.
While testimony in this day is individual in a certain sense, yet if one finds himself where the Lord is he will of necessity be with others who are in the same place—in this it becomes collective.
The same things are seen in 2 Tim. 2 where this present day of Church defilement and ruin is described: "Let every one that nameth the name of Christ [the Lord] depart from iniquity," and "follow... with them that call on the Lord out of a pure heart." vv. 19-22.
Today each Christian—one who names the name of the Lord—has individual responsibility for separation from iniquity and of seeking the Lord, but let no one say there is no such thing left as corporate or collective testimony; find the Lord and those seeking Him only, in separation from evil, and you will find corporate testimony as well.