Add a test case for LabelAlignment

tests/test_core.py

@@ -43,10 +43,29 @@ def test_labels_unchanged_after_encoding_and_decoding(
     assert labels == label_set.decode(label_set.encode_to_tag_indices(labels))
 
 
-@pytest.fixture()
-def alignment() -> LabelAlignment:
+@st.composite
+def target_label(draw: st.DrawFn) -> SequenceLabel:
+    size = 9
+    num_tags = draw(st.integers(min_value=1, max_value=5))
+    tags = []
+    last = 1
+    for _ in range(num_tags):
+        if last >= size:
+            break
+        start = draw(st.integers(min_value=last, max_value=size - 1))
+        end = draw(st.integers(min_value=start + 1, max_value=size))
+        label = draw(st.sampled_from(["ORG", "LOC", "PER", "MISC"]))
+        # NOTE: mypy cannot infer a type of the dictionary below.
+        tags.append(cast(TagDict, {"start": start, "end": end, "label": label}))
+        last = end + 1
+
+    return SequenceLabel.from_dict(tags=tags, size=size + 1, base=Base.TARGET)
+
+
+@given(label=target_label())
+def test_labels_unchanged_after_alignment(label: SequenceLabel) -> None:
     # Tokenized by RoBERTa
-    return LabelAlignment(
+    alignment = LabelAlignment(
         (
             None,
             Span(0, 3),
@@ -93,6 +112,10 @@ def alignment() -> LabelAlignment:
         ),
     )
 
+    assert label == alignment.align_with_target(
+        label=alignment.align_with_source(label=label)
+    )
+
 
 def test_tags_define_in_truncated_part_ignored() -> None:
     truncated_alignment = LabelAlignment(