TST: refactor constants and clarify comments.
TST: clean up/extract constants in tests.
MAINT: add/modify constants.
MAINT: remove obsolete and alphabetize.
MAINT: clean up.
MAINT: modify constants to have named params.
MAINT: extract constants.
STY: fix indentation.
MAINT: refactor common part out of buyback_auth.
MAINT: refactor earnings test logic.