Jesus told Nicodemus that he was looking for heavenly things but did not understand earthly things and that the only message that has come from heaven is
14 And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:
15 That whosoever believeth in him should not perish, but have eternal life.
16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved [fear that God is going to get them].
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God. [or those who end up coming to God instead of finding a condemning God find that their lives change.]
This indicates to me that the straight testimony deals with God and his relationship with the world and us and our relationship with God and the world.
This can lead into 1 John 2 15 to 17:
15 Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him.
16 For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.
17 And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever.
Now most of us do an excellent job with 1 John 2:15. We run into trouble with verses 16 and 17. Most of us think we are for ourselves by making less of the outside world. Much of religion has been where we can use it to control others and for us to think "At least I'm not like..." and we have our list of does and don'ts. Some have a very long list of does and don'ts others have a very short list "All you have to do is say the magic words about accepting Jesus as your Lord and savior and you are saved, there is nothing else [except become a militant far right Republican and throw your energy into getting the law to push our views on to others.]
Verse 16 tells us that what it is in the world we are not to love is not the world out there, but something inside of each and every one of us that wants things to be exactly the way we want them to be and how we manipulate others instead of cooperating with what reality has to offer. Most people either want a religion where there is no change in our lives, and others where the changes tend to be controlling others and to interpret reality in a way that soothes our ego instead of really reaching out and loving the world as God has loved it. This will shake others out because you will have those who don't want to change who just wants to say the right words to get into heaven and they want to be saved in their present sins. And you will have another group who wants to see the gospel as the good news that everyone else is going to hell in a hand basket, and where they can have headship and control. They don't want the changes the Bible calls for.