feat(mnemonic): improve invalid size test strategies

Refactor property-based tests for mnemonic generation to better handle
invalid word counts. Ensures zero is excluded from wrong count cases and
removes redundant hypothesis assumptions. This enhances test clarity and
coverage for edge cases.

Author: mkoura

cardano_node_tests/tests/test_mnemonic.py

@@ -160,8 +160,8 @@ def maybe_reencode(text: str) -> st.SearchStrategy[bytes]:
 @st.composite
 def wrong_count_files(draw: st.DrawFn) -> BadMnemonicCase:
     """Wrong number of words (not in {12, 15, 18, 21, 24})."""
-    count = draw(st.integers(min_value=0, max_value=48).filter(lambda n: n not in _ALLOWED_COUNTS))
-    hypothesis.assume(count != 0)  # Zero handled by empty_file elsewhere
+    # Zero handled by empty_file elsewhere
+    count = draw(st.integers(min_value=1, max_value=48).filter(lambda n: n not in _ALLOWED_COUNTS))
     tokens = draw(word_sequence(count=count, ensure_invalid=False))
     line = draw(join_with_weirdness(tokens=tokens))
     content = draw(maybe_reencode(line))
@@ -429,7 +429,7 @@ def tmp_case_path(self) -> tp.Generator[pl.Path, None, None]:
         shutil.rmtree(d)
 
     @allure.link(helpers.get_vcs_link())
-    @hypothesis.given(size=st.integers())
+    @hypothesis.given(size=st.integers().filter(lambda n: n not in _ALLOWED_COUNTS))
     @common.hypothesis_settings(max_examples=1_000)
     @pytest.mark.smoke
     def test_gen_invalid_size(
@@ -438,8 +438,6 @@ def test_gen_invalid_size(
         size: int,
     ):
         """Test generating a mnemonic with an invalid size."""
-        hypothesis.assume(size not in _ALLOWED_COUNTS)
-
         common.get_test_id(cluster)
         with pytest.raises(clusterlib.CLIError) as excinfo:
             cluster.g_key.gen_mnemonic(size=size)  # type: ignore