feat: add comprehensive unit tests for FragmentClient methods; include shared test constants

tests/shared.py

@@ -0,0 +1,23 @@
+"""Shared test constants — imported by all test modules that need them."""
+
+from typing import Any
+
+# Shared test credentials
+
+VALID_SEED: str = "abandon " * 23 + "about"
+VALID_API_KEY: str = "A" * 68
+VALID_COOKIES: dict[str, str] = {
+    "stel_ssid": "x",
+    "stel_dt": "x",
+    "stel_token": "x",
+    "stel_ton_token": "x",
+}
+
+# Fake values for mocked tests
+
+FAKE_HASH: str = "abc123"
+FAKE_RECIPIENT: str = "recipient_token"
+FAKE_REQ_ID: str = "req_42"
+FAKE_TX_HASH: str = "deadbeef" * 8
+FAKE_ACCOUNT: dict[str, Any] = {"address": "0:abc", "publicKey": "pub", "chain": "-239", "walletStateInit": "base64=="}
+FAKE_TRANSACTION: dict[str, Any] = {"transaction": {"messages": [{"address": "0:abc", "amount": "100000000", "payload": ""}]}}