test(tx_basic): assert fee info in tx build stdout

Add assertion to check that the transaction build command's stdout contains
Lovelace fee information. This ensures that fee details are present in the
output, improving test coverage.

Author: mkoura

cardano_node_tests/tests/test_tx_basic.py

@@ -967,7 +967,7 @@ def test_build_multiple_same_txins(
             txins=tx_raw_output.txins, txouts=tx_raw_output.txouts
         )
 
-        cluster.cli(
+        out = cluster.cli(
             [
                 "transaction",
                 "build",
@@ -985,6 +985,9 @@ def test_build_multiple_same_txins(
         )
         assert tx_raw_output.out_file.exists()
 
+        stdout_dec = out.stdout.strip().decode("utf-8") if out.stdout else ""
+        assert " Lovelace" in stdout_dec, "Fee information not found in stdout"
+
     @allure.link(helpers.get_vcs_link())
     @pytest.mark.skipif(
         VERSIONS.transaction_era < VERSIONS.ALONZO,