No-confidence motion tests ruling government's majority in Lok Sabha.
INDIA alliance files motion against Modi government over Manipur violence.
Rules require minimum 50 members' support and debate within 10 days.
Opposition's motion unlikely to succeed with ruling party's clear majority.
History shows most motions defeated, but some led to significant political developments.
Indira Gandhi faced most motions during her tenure but survived each one.
2018 no-confidence motion against Modi-led NDA government was unsuccessful.