test: Add unit tests for ParseNumberFromBrackets (#3878)

* test: Add unit tests for ParseNumberFromBrackets

pyiceberg/utils/parsing.py was the only module under pyiceberg/utils
without a dedicated test. ParseNumberFromBrackets backs parsing of
bucket[N], truncate[N] and fixed[L], so cover its match behaviour and the
ValidationError raised on malformed input.

* test: Assert the exact error message and drop redundant cases

Verify the full ValidationError message for the invalid-input cases and
parametrize them. Remove the multi-digit case (already covered) and the
cases that relied on re.search tolerating text around the pattern.

Author: damansingh1313

tests/utils/test_parsing.py

@@ -0,0 +1,42 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+import pytest
+
+from pyiceberg.exceptions import ValidationError
+from pyiceberg.utils.parsing import ParseNumberFromBrackets
+
+
+def test_match_returns_the_bracketed_number() -> None:
+    assert ParseNumberFromBrackets("fixed").match("fixed[22]") == 22
+    assert ParseNumberFromBrackets("bucket").match("bucket[8]") == 8
+    assert ParseNumberFromBrackets("truncate").match("truncate[16]") == 16
+
+
+@pytest.mark.parametrize(
+    "prefix, value",
+    [
+        pytest.param("fixed", "decimal[8]", id="wrong-prefix"),
+        pytest.param("fixed", "fixed", id="missing-brackets"),
+        pytest.param("truncate", "truncate[abc]", id="non-numeric"),
+        pytest.param("truncate", "truncate[-1]", id="negative"),
+    ],
+)
+def test_match_raises_with_expected_message(prefix: str, value: str) -> None:
+    with pytest.raises(ValidationError) as exc_info:
+        ParseNumberFromBrackets(prefix).match(value)
+    assert str(exc_info.value) == f"Could not match {value}, expected format {prefix}[22]"