test: raise an error if output value is <= 0 in create_self_transfer

Author: ismaelsadeeq

test/functional/test_framework/wallet.py

@@ -378,7 +378,8 @@ def create_self_transfer(
         if target_vsize and not fee:  # respect fee_rate if target vsize is passed
             fee = get_fee(target_vsize, fee_rate)
         send_value = utxo_to_spend["value"] - (fee or (fee_rate * vsize / 1000))
-
+        if send_value <= 0:
+            raise RuntimeError(f"UTXO value {utxo_to_spend['value']} is too small to cover fees {(fee or (fee_rate * vsize / 1000))}")
         # create tx
         tx = self.create_self_transfer_multi(
             utxos_to_spend=[utxo_to_spend],