Test jsonpath simple field name

tests/common/test_jsonpath.py

@@ -0,0 +1,43 @@
+import pytest
+
+from dlt.common import jsonpath as jp
+
+
+@pytest.mark.parametrize("compiled", [True, False])
+@pytest.mark.parametrize(
+    "path, expected",
+    [
+        ("col_a", "col_a"),
+        ("'col.a'", "col.a"),
+        ("'$col_a'", "$col_a"),
+        ("'col|a'", "col|a"),
+    ],
+)
+def test_extract_simple_field_name_positive(path, expected, compiled):
+    if compiled:
+        path = jp.compile_path(path)
+
+    result = jp.extract_simple_field_name(path)
+    assert result == expected
+
+
+@pytest.mark.parametrize("compiled", [True, False])
+@pytest.mark.parametrize(
+    "path",
+    [
+        "$.col_a",
+        "$.col_a.items",
+        "$.col_a.items[0]",
+        "$.col_a.items[*]",
+        "col_a|col_b",
+    ],
+)
+def test_extract_simple_field_name_negative(path, compiled):
+    if compiled:
+        path = jp.compile_path(path)
+
+    result = jp.extract_simple_field_name(path)
+    assert result is None
+
+
+# TODO: Test all jsonpath utils