The Tests

In the beginning of the book I detailed the tests I would use.  These are all based in some way, on The Bible.  If they are based on anything else they would be useless for the purposes of evaluating Christian doctrine and practice.
Test 1
The Bible either commends the belief or practice or condemns it.  The matter wholly or partly fails this test.
This is the basic Test. If the belief or practice is not mentioned in the Bible then it must pass the principles in the Bible (Test 2).
People point to apostolic tradition as a basis for the beliefs or practices that they do. Regardless of it being apostolic practice it must  still pass the tests of the Bible or the second set of tests if The Bible is silent on the matter.
You cannot half obey The Bible.  So something will pass or fall in its entirety if it is not divisible.  If it is divisible into smaller sections then parts of the whole may pass The Bible test so what parts of the whole do not pass this test must then pass the pars of test two.
The parts of test two
The only command Jesus gave us was The Law of Love (John 13:34-35).  All other commands flow from this law.
Salvation is a love relationship with Jesus and the Father so anything that displaces Jesus as Lord is sin and idolatry and may destroy a person’s salvation relationship. This is the rationale behind the first part of the second test
Anything that is not of love is sin and breaks the command Jesus gave us.  This is the rationale behind the second part of the second test.
The third test deals with the expression of our love towards others where something we do or promote causes another to stumble.  Jesus warned against this and declared you were in real danger of losing your salvation if you knowingly caused another to sin.
This is the rationale behind the third part of the second test.
If the practice fails any of these tests then to knowingly continue in it is sin.
If it is not mentioned in the Bible and does not fail any of the tests then the practice can be continued but not as the doctrine as doctrine is God inspired (Job 32:8) and will be in the Bible if God wanted you to believe in it. So if it is not in  The Bible it cannot be doctrine but will be only be the musings of man.
Using the example of the Mass:
The activity of reading of The Bible in the format it is done in the Mass is not in The Bible but the contents of the activity (The Bible) is so this would pass the second test.  You should not confuse the authorisation of a part with the activity in that part.  The activity itself may not be in The Bible so that it is needs to pass the second test but the actual contents may be either confirmed or condemned by The Bible so it would fail the first test.

There are two parts to the second test.  Does the activity pass the test?
Does the content of the activity pass both tests?

Usually both parts are the same but sometimes they need to be examined separately.
A final point to make is that any matter passing the parts of the second test can be an individual or church practice and if it is a contentious one you may have individuals in the church believing it and others knowing the truth about its error not practicing it.  Matters passing the parts of the second test are really a matter of personal belief and no church has a right to force these beliefs onto anyone.  To do so is sin as it goes against The Law of Love.