check_if_number util function handles None, and add test (#257)

src/fmu/dataio/_utils.py

@@ -282,6 +282,9 @@ def nested_parameters_dict(
 def check_if_number(value):
     """Check if value (str) looks like a number and return the converted value."""
 
+    if value is None:
+        return
+
     res = None
     try:
         res = int(value)

tests/test_units/test_utils.py

@@ -0,0 +1,27 @@
+"""Test the utils module"""
+
+import pytest
+
+from fmu.dataio import _utils as utils
+
+
+@pytest.mark.parametrize(
+    "value, result",
+    [
+        (None, None),
+        ("0", 0),
+        ("1", 1),
+        ("1.0", 1.0),
+        ("0.0", 0.0),
+        ("-1", -1),
+        ("-1.0", -1.0),
+        ("-999", -999),
+        ("-999.12345678", -999.12345678),
+        ("9999999999999999", 9999999999999999),
+        ("abc", "abc"),
+        (False, False),
+        (True, True),
+    ],
+)
+def test_check_if_number(value, result):
+    assert utils.check_if_number(value) == result