diff --git a/tests/test_utils_messages.py b/tests/test_utils_messages.py
new file mode 100644
index 0000000..db1a3b4
--- /dev/null
+++ b/tests/test_utils_messages.py
@@ -0,0 +1,72 @@
+import os
+from datetime import datetime, UTC
+import pytest
+
+import utils
+import messages
+
+
+def decode_fix(msg: bytes) -> dict[str, str]:
+    string = msg.decode('utf-8').replace('\x01', '|')
+    return utils.get_attrs(string)
+
+
+def test_get_attrs_and_get_attr():
+    msg = "8=FIX.4.4|35=D|49=CLIENT|56=PT-OE|11=123|"
+    attrs = utils.get_attrs(msg)
+    assert attrs["8"] == "FIX.4.4"
+    assert utils.get_attr(msg, "35") == "D"
+    assert utils.get_attr(msg, "99") is None
+
+
+def test_format_epoch_time():
+    assert utils.format_epoch_time(0) == "19700101-00:00:00.000"
+
+
+def test_get_log_filename(monkeypatch):
+    fixed = datetime(2024, 1, 2, 3, 4, 5, tzinfo=UTC)
+
+    class DummyDatetime:
+        @classmethod
+        def utcnow(cls):
+            return fixed
+
+    monkeypatch.setattr(utils, "datetime", DummyDatetime)
+    filename = utils.get_log_filename("prefix")
+    assert filename == "prefix_20240102_030405.log"
+
+
+def test_generate_jwt_success(monkeypatch):
+    os.environ["API_SECRET"] = "secret"
+    os.environ["API_URI"] = "uri"
+    monkeypatch.setattr(utils.jwt, "encode", lambda p, k, algorithm=None: "TOKEN")
+    assert utils.generateJWT("api", 123) == "TOKEN"
+
+
+def test_getMsgHeartbeat_and_errors():
+    with pytest.raises(AssertionError):
+        messages.getMsgHeartbeat(None, 3)
+    with pytest.raises(AssertionError):
+        messages.getMsgHeartbeat("api", 2)
+
+    msg = messages.getMsgHeartbeat("api", 3)
+    attrs = decode_fix(msg)
+    assert attrs["35"] == "0"
+    assert attrs["34"] == "3"
+    assert attrs["49"] == "api"
+
+
+def test_getMsgLogon(monkeypatch):
+    monkeypatch.setattr(messages, "generateJWT", lambda a, n: "TOK")
+    msg = messages.getMsgLogon("api")
+    attrs = decode_fix(msg)
+    assert attrs["35"] == "A"
+    assert attrs["49"] == "api"
+    assert attrs["554"] == "TOK"
+
+
+def test_translateFix_cases():
+    assert messages.translateFix("35", "D") == "New Order - Single"
+    assert messages.translateFix("39", "4") == "Cancelled"
+    assert "UNKNOWN Fix key" in messages.translateFix("35", "Z")
+    assert "UNKNOWN Fix field" in messages.translateFix("99", "1")