Clarify that using a header in library/ rather than include/ for
internal functions is a rule, not just a possibility.
As suggested by Manuel, state a rule for functions that need to be
static for best optimization but that we want to unit-test.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Evaluate possible approaches for invasive testing.
State some rules.
This commit was originally written for Mbed Crypto only.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>