message: Add extra check for validator balance.
diff: @@ -1537,6 +1537,10 @@ fn should_undelegate_delegators_when_validator_unbonds() {
  );
  // Process unbonding requests to verify delegators recevied their stakes
  + let validator_1 = builder
  + .get_account(*VALIDATOR_1_ADDR)
  + .expect("should have validator 1 account");
  + let validator_1_balance_before = builder.get_purse_balance(validator_1.main_purse());
  let delegator_1 = builder
  .get_account(*DELEGATOR_1_ADDR)
  @@ -1553,9 +1557,14 @@ fn should_undelegate_delegators_when_validator_unbonds() {
  timestamp_millis += TIMESTAMP_MILLIS_INCREMENT;
  }
  + let validator_1_balance_after = builder.get_purse_balance(validator_1.main_purse());
  let delegator_1_balance_after = builder.get_purse_balance(delegator_1.main_purse());
  let delegator_2_balance_after = builder.get_purse_balance(delegator_2.main_purse());
  + assert_eq!(
  + validator_1_balance_before + U512::from(VALIDATOR_1_STAKE),
  + validator_1_balance_after
  + );
  assert_eq!(
  delegator_1_balance_before + U512::from(DELEGATOR_1_STAKE),
  delegator_1_balance_after
  @@ -1722,6 +1731,10 @@ fn should_undelegate_delegators_when_validator_fully_unbonds() {
  );
  // Process unbonding requests to verify delegators recevied their stakes
  + let validator_1 = builder
  + .get_account(*VALIDATOR_1_ADDR)
  + .expect("should have validator 1 account");
  + let validator_1_balance_before = builder.get_purse_balance(validator_1.main_purse());
  let delegator_1 = builder
  .get_account(*DELEGATOR_1_ADDR)
  @@ -1738,9 +1751,14 @@ fn should_undelegate_delegators_when_validator_fully_unbonds() {
  timestamp_millis += TIMESTAMP_MILLIS_INCREMENT;
  }
  + let validator_1_balance_after = builder.get_purse_balance(validator_1.main_purse());
  let delegator_1_balance_after = builder.get_purse_balance(delegator_1.main_purse());
  let delegator_2_balance_after = builder.get_purse_balance(delegator_2.main_purse());
  + assert_eq!(
  + validator_1_balance_before + U512::from(VALIDATOR_1_STAKE),
  + validator_1_balance_after
  + );
  assert_eq!(
  delegator_1_balance_before + U512::from(DELEGATOR_1_STAKE),
  delegator_1_balance_after
  