Improvements and perspective from architecture review

tests/test_document_functions.py

@@ -60,6 +60,13 @@ def test_pipeline_passes_previous_output_to_next_function():
     assert result.content == "Final"
 
 
+def test_pipeline_separator_inside_quotes_is_literal():
+    result = render_document_functions('{{mkt:text.replace "a|b" "|" "/"}}')
+
+    assert result.valid
+    assert result.content == "a/b"
+
+
 def test_context_variables_can_be_used_in_function_arguments():
     context = ProcessingContext(variables={"title": "Architecture Decision"})
 
@@ -75,6 +82,13 @@ def test_validate_document_functions_reports_forbidden_calls():
     assert result.diagnostics[0].code == "function.forbidden"
 
 
+def test_validate_document_functions_reports_argument_errors():
+    result = validate_document_functions("{{mkt:text.upper draft unexpected=value}}")
+
+    assert not result.valid
+    assert result.diagnostics[0].code == "function.arguments"
+
+
 def test_registry_can_expose_custom_function_without_core_rewrite():
     registry = DocumentFunctionRegistry()
     registry.register(