- Even within the Bible, spiritual gifts are not clearly and definitively defined. Paul covers the topic several times. The moral of each passage is the same; that God has given you abilities to use for his glory and the betterment of the Church. But each list he gives is different. Do you compile a test for all of them mentioned across the various epistles? The core gifts that appear in multiple lists?
- Many of the gifts are charismatic in nature. Lots of denominations don't think people will start spouting Jeremiah style Prophecy, so they reinterpret it as "speaking God's truth" (e.g. scripture application). Is that correct? Maybe. We really don't know what the Old Testament College of Prophets looked like. Most of the prophets we have records for are not the everyday sort, they're the once in a generation world-changers. Demanding direct connection with God might be like saying everyone with the gift of Evangelism ought to be Billy Graham. Or it might not.
- Theological issues aside, most of these tests are actually based on aptitude or inclination not spiritual ability. They're often little more than personality tests. You like to talk to people? Be an evangelist or a pastor/shepherd. You're bookish? Then teach. You like to help meet physical needs: you're a servant. But is that the gift God has given you? Not necessarily. Worse yet, the whole structure of the test is driven by your own perceptions of yourself, which may or may not be accurate. Think of all those American Idol contestants who really think they can sing.
If you want to use these things in your church, just call them what they are, aptitude or personality tests. Explain to people that they can help them figure out their talents so they can use them to better the Kingdom, but that they aren't some sort of definitive source for spiritual insight and they don't absolve them of spiritual responsibility.