Add tests for field id clashes

glowtables/tests/table_test.py

@@ -14,6 +14,7 @@
 
 import textwrap
 
+import pytest
 import rdflib
 
 from glowtables.table import Language, LiteralField, Table
@@ -90,3 +91,35 @@ def test_default_value() -> None:
         }
         """
     )
+
+
+def test_field_id_subject() -> None:
+    name_field = LiteralField(
+        "subject",
+        {Language("en"): "Name"},
+        rdflib.URIRef("http://example.org/display-name"),
+    )
+    with pytest.raises(ValueError, match="both subject and a field id"):
+        Table(
+            fields=[name_field],
+            constraints="",
+        )
+
+
+def test_field_id_clash() -> None:
+    name_field = LiteralField(
+        "name",
+        {Language("en"): "Name"},
+        rdflib.URIRef("http://example.org/name"),
+    )
+    display_name_field = LiteralField(
+        "name",
+        {Language("en"): "Display Name"},
+        rdflib.URIRef("http://example.org/display-name"),
+    )
+    with pytest.raises(ValueError, match="has duplicate field ids: name"):
+        Table(
+            fields=[name_field, display_name_field],
+            constraints="",
+        )
+