feat(tests): adding assert_tx_matches() to common.py

docs/tests/device-tests.md

@@ -57,6 +57,12 @@ If you would like to interact with the device (i.e. press the buttons yourself),
 INTERACT=1 pytest tests/device_tests
 ```
 
+When testing transaction signing, there is an option to check transaction hashes on-chain using Blockbook. It is chosen by setting `CHECK_ON_CHAIN=1` environment variable before running the tests.
+
+```sh
+CHECK_ON_CHAIN=1 pytest tests/device_tests
+```
+
 To run the tests quicker, spawn the emulator with disabled animations using `-a` flag.
 
 ```sh

tests/common.py

@@ -15,9 +15,12 @@
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
 import json
+import os
+from decimal import Decimal
 from pathlib import Path
 
 import pytest
+import requests
 
 from trezorlib import btc, tools
 from trezorlib.messages import ButtonRequestType as B
@@ -222,3 +225,26 @@ def get_test_address(client):
     """Fetch a testnet address on a fixed path. Useful to make a pin/passphrase
     protected call, or to identify the root secret (seed+passphrase)"""
     return btc.get_address(client, "Testnet", TEST_ADDRESS_N)
+
+
+def assert_tx_matches(serialized_tx: bytes, hash_link: str, tx_hex: str = None) -> None:
+    """Verifies if a transaction is correctly formed."""
+    hash_str = hash_link.split("/")[-1]
+    assert tools.tx_hash(serialized_tx).hex() == hash_str
+
+    if tx_hex:
+        assert serialized_tx.hex() == tx_hex
+
+    # TODO: we could probably do better than os.environ, this was the easiest solution
+    # (we could create a pytest option (and use config.getoption("use-blockbook")),
+    # but then each test would need to have access to config via function argument)
+    if int(os.environ.get("CHECK_ON_CHAIN", 0)):
+
+        def get_tx_hex(hash_link: str) -> str:
+            tx_data = requests.get(
+                hash_link, headers={"User-Agent": "BTC transactions test"}
+            ).json(parse_float=Decimal)
+
+            return tx_data["hex"]
+
+        assert serialized_tx.hex() == get_tx_hex(hash_link)

tests/conftest.py

@@ -27,6 +27,9 @@ from . import ui_tests
 from .device_handler import BackgroundDeviceHandler
 from .ui_tests.reporting import testreport
 
+# So that we see details of failed asserts from this module
+pytest.register_assert_rewrite("tests.common")
+
 
 @pytest.fixture(scope="session")
 def _raw_client(request):