Demonstrate incorrect CQL2 "LIKE" conversion behavior

Author: kurtmckee

stac_fastapi/tests/extensions/test_cql2_like_to_es.py

@@ -0,0 +1,46 @@
+import pytest
+
+from stac_fastapi.core.extensions.filter import cql2_like_to_es
+
+
+@pytest.mark.parametrize(
+    "cql2_value, expected_es_value",
+    (
+        # no-op
+        ("", ""),
+        # backslash
+        ("\\\\", "\\"),
+        # percent
+        ("%", "*"),
+        (r"\%", "%"),
+        (r"\\%", r"\*"),
+        (r"\\\%", r"\%"),
+        # underscore
+        ("_", "?"),
+        (r"\_", "_"),
+        (r"\\_", r"\?"),
+        (r"\\\_", r"\_"),
+    ),
+)
+def test_cql2_like_to_es_success(cql2_value: str, expected_es_value: str) -> None:
+    """Verify CQL2 LIKE query strings are converted correctly."""
+
+    assert cql2_like_to_es(cql2_value) == expected_es_value
+
+
+@pytest.mark.parametrize(
+    "cql2_value",
+    (
+        pytest.param("\\", id="trailing backslash escape"),
+        pytest.param("\\1", id="invalid escape sequence"),
+    ),
+)
+def test_cql2_like_to_es_invalid(cql2_value: str) -> None:
+    """Verify that incomplete or invalid escape sequences are rejected.
+
+    CQL2 currently doesn't appear to define how to handle invalid escape sequences.
+    This test assumes that undefined behavior is caught.
+    """
+
+    with pytest.raises(ValueError):
+        cql2_like_to_es(cql2_value)