Add property-based testing with Hypothesis

pyproject.toml

@@ -32,7 +32,7 @@ Homepage = "https://github.com/gijzelaerr/python-snap7"
 Documentation = "https://python-snap7.readthedocs.io/en/latest/"
 
 [project.optional-dependencies]
-test = ["pytest", "pytest-asyncio", "pytest-cov", "pytest-html", "mypy", "types-setuptools", "ruff", "tox", "tox-uv", "types-click", "uv"]
+test = ["pytest", "pytest-asyncio", "pytest-cov", "pytest-html", "hypothesis", "mypy", "types-setuptools", "ruff", "tox", "tox-uv", "types-click", "uv"]
 cli = ["rich", "click" ]
 doc = ["sphinx", "sphinx_rtd_theme"]
 
@@ -52,6 +52,7 @@ markers =[
     "client",
     "common",
     "e2e: end-to-end tests requiring a real PLC connection",
+    "hypothesis: property-based tests using Hypothesis",
     "logo",
     "mainloop",
     "partner",

snap7/util/getters.py

@@ -660,15 +660,38 @@ def get_ldt(bytearray_: Buffer, byte_index: int) -> datetime:
 
 
 def get_dtl(bytearray_: Buffer, byte_index: int) -> datetime:
+    """Get DTL (Date and Time Long) value from bytearray.
+
+    Notes:
+        Datatype ``DTL`` consists of 12 bytes in the PLC:
+        - Bytes 0-1: Year (uint16, big-endian)
+        - Byte 2: Month (1-12)
+        - Byte 3: Day (1-31)
+        - Byte 4: Weekday (1=Sunday, 7=Saturday)
+        - Byte 5: Hour (0-23)
+        - Byte 6: Minute (0-59)
+        - Byte 7: Second (0-59)
+        - Bytes 8-11: Nanoseconds (uint32, big-endian)
+
+    Args:
+        bytearray_: buffer to read from.
+        byte_index: byte index from where to start reading.
+
+    Returns:
+        datetime value (microsecond precision; sub-microsecond nanoseconds are truncated).
+    """
+    nanoseconds = struct.unpack(">I", bytearray_[byte_index + 8 : byte_index + 12])[0]
+    microsecond = nanoseconds // 1000
+
     time_to_datetime = datetime(
         year=int.from_bytes(bytearray_[byte_index : byte_index + 2], byteorder="big"),
         month=int(bytearray_[byte_index + 2]),
         day=int(bytearray_[byte_index + 3]),
         hour=int(bytearray_[byte_index + 5]),
         minute=int(bytearray_[byte_index + 6]),
         second=int(bytearray_[byte_index + 7]),
-        microsecond=int(bytearray_[byte_index + 8]),
-    )  # --- ? noch nicht genau genug
+        microsecond=microsecond,
+    )
     if time_to_datetime > datetime(2554, 12, 31, 23, 59, 59):
         raise ValueError("date_val is higher than specification allows.")
     return time_to_datetime

snap7/util/setters.py

@@ -534,7 +534,7 @@ def set_date(bytearray_: Buffer, byte_index: int, date_: date) -> Buffer:
     elif date_ > date(2168, 12, 31):
         raise ValueError("date is higher than specification allows.")
     _days = (date_ - date(1990, 1, 1)).days
-    bytearray_[byte_index : byte_index + 2] = struct.pack(">h", _days)
+    bytearray_[byte_index : byte_index + 2] = struct.pack(">H", _days)
     return bytearray_
 
 
@@ -595,6 +595,12 @@ def set_wstring(bytearray_: Buffer, byte_index: int, value: str, max_size: int =
     if max_size > 16382:
         raise ValueError(f"max_size: {max_size} > max. allowed 16382 chars")
 
+    if any(ord(c) > 0xFFFF for c in value):
+        raise ValueError(
+            "Value contains characters outside the Basic Multilingual Plane (codepoint > U+FFFF), "
+            "which are not supported by the PLC WSTRING type."
+        )
+
     size = len(value)
     if size > max_size:
         raise ValueError(f"size {size} > max_size {max_size}")
@@ -632,7 +638,7 @@ def set_tod(bytearray_: Buffer, byte_index: int, tod: timedelta) -> Buffer:
     """
     if tod.days >= 1 or tod < timedelta(0):
         raise ValueError("TIME_OF_DAY must be between 00:00:00.000 and 23:59:59.999")
-    ms = int(tod.total_seconds() * 1000)
+    ms = (tod.days * 86400 + tod.seconds) * 1000 + tod.microseconds // 1000
     bytearray_[byte_index : byte_index + 4] = ms.to_bytes(4, byteorder="big")
     return bytearray_