A good test of doctrine is its age. Jude tells us that the Christian faith was "once for all delivered to the saints" in the first century. This tells us that we are expecting nothing new. Anything that evolved after the death of the last apostle must necessarily be man made, particularly those that directly contradict the scriptures.
When Jesus walked the earth, He had a very specific message: "It is written" and "it must be fulfilled". Although there is plenty in the New Testament that is "new" (at least in the sense it wasn't exactly known to Adam and Eve), the Old Testament contains prophecy after prophecy, revelation after revelation, promises and warnings. As Amos said, God does nothing without revealing His secret to His prophets (Amos 3:7). Thus, everything in the New Testament has some kind of grounding in the Old. Jesus should have taken no one by surprise, and we see He constantly scolded people for being surprised by Him.
We, today, should have the same attitude. We must appeal to "it is written", and "it will be fulfilled", not "it is said". The scriptures are now complete, and every doctrine a Christian will ever need has been completely solidified for nearly 2,000 years. But many religions have arisen since then claiming to have extra revelation, or to abrogate old ones.
Catholicism, for example, has been evolving since its origins around the fourth century. In times past, the concept of a Pope was completely alien, and even when it evolved, it was nothing like it would go on to become. Purgatory and transubstantiation both still belonged to the Roman pagans. It wasn't until the 13th century that the Catholic Church became what it is today, and even the concept of abrogation still persists. For example, Canon 6 of the 1983 Code of Canon Law stated that anything in the 1917 Code of Canon Law that was not renewed in 1983 has been "abrogated". In other words, the Catholic Church can change almost on a whim right now. Does this sound like a religion that was delivered "once for all" to the saints?
Another religion that's very fond of the concept of abrogation is Islam, another religion that popped up long after Christianity, yet nevertheless claims to be a continuation thereof. Muhammad actually claimed to be mentioned by name in the Torah and the Gospel. Yet, much like Catholicism, Muhammad brought new doctrines, most of which were contrary to the scriptures. Again, this is not a faith that was delivered "once for all" in the first century.
The 19th century saw the rise of many religions. Two notable examples are Mormonism (1830) and the Watchtower organisation (1884). Naturally, both of these Trinity denying cults brought a host of crazy doctrines so alien to the actual scriptures that entirely new "scriptures" needed to be written, and in the case of the Watchtower Society, a brand new Bible had to be "translated". Mormonism even formulated the concept of a "Great Apostasy", meaning that Jesus and the Apostles actually failed in their mission, leaving the real religion completely absent from the world (except for the Apostle John, who allegedly was given immortality and is alive to this day, according to D&C 7:1-3) until it was "restored" by Joseph Smith.
Another religion that popped up in the 19th century is Evolution (1859), and although Evolution itself never claimed affiliation with Christianity, and indeed was designed to compete with it, many Christians decided to abandon orthodox Creation beliefs and attempt to merge it with the Bible. Creationism is one of the oldest doctrines in the entire Christian faith, being the very first doctrine in the Torah, and woven throughout the scriptures. For over 3,400 years, the origins of the heavens, the earth and all that are in them have been solidified in the scriptures, having been delivered to Moses, the prophets and the Apostles by none other than God Himself (2 Timothy 3:16-17; 2 Peter 1:20-21), and it was the overwhelmingly dominant view throughout history. Nevertheless, many Christians decided to discard this irrefutable fact and crowbar Darwinian fiction into Genesis in a number of ways, none of which I intend to go into right now.
But if such an explicit doctrine can be so easily stricken from Christianity, why can't other doctrines also be removed? As more churches accept Evolution, these same churches swiftly become what is often sarcastically referred to as a "sinagogue". Sound doctrine is becoming increasingly difficult to find, and even powerful apologists such as William Lane Craig, who calls Creationism "embarrassing", are far less willing to stand on the inerrancy of scripture. Whereas Jude tells us the faith was delivered "once for all" to the saints, modern Christians insist that the Church must adapt to the culture. I was even recently told by one such Christian(?) that the Bible was written by fallible men in an imperfect attempt to discern the will of God, and thus she couldn't reconcile what she calls "homophobia" (of course defined as even the most loving opposition to homosexuality) with her god. Yet, acting on the Biblical definition of marriage and the condemnation of homosexuality in the scriptures, 3,400 years worth of Jews and Christians have been incapable of reconciling homosexuality with the scriptures either. This is an entirely new concept.
The scriptures are quite clear: Christianity is not expected to change. The faith we have today should look no different from the faith the Apostles preached. Anything that does is, put simply, not Christian. New doctrines, and especially new religions, are to be discarded at the drop of a hat. They are man made myths intended, whether by the author or the devil, to distract mankind from the God of our salvation.