Move syntax processing equivalence test to its own file

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
SyntaxProcessorTest: add another test, complete an existing one

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
SyntaxProcessorTest: factorize a lot of code

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>