add test removing all shares

fdas

Author: wphan

programs/drift/src/math/insurance/tests.rs

@@ -165,4 +165,13 @@ pub fn if_shares_lost_test() {
             < if_stake.last_withdraw_request_value,
         true
     );
+
+    // removing 100% of shares
+    spot_market.insurance_fund.total_shares = 1000 * QUOTE_PRECISION;
+    if_stake.update_if_shares(1000 * QUOTE_PRECISION, &spot_market).unwrap();
+    if_stake.last_withdraw_request_value = (1000 * QUOTE_PRECISION - 1) as u64;
+    if_stake.last_withdraw_request_shares = 1000 * QUOTE_PRECISION;
+    let lost_shares = calculate_if_shares_lost(&if_stake, &spot_market, if_balance).unwrap();
+
+    assert_eq!(lost_shares, 0);
 }