These tests verify interactions between the database engine and TVFs.
They happen to use generate_series, but they are not intended to test
the behavior of any specific extension. Tests that verify generate_series
specific behavior remain in extensions.py.
When adding tests for extensions, please follow these guidelines:
Tests that verify the internal logic or behavior of a particular extension should go into cli_tests/extensions.py.
Tests that verify how extensions interact with the database engine, such as virtual table handling, should be written
in TCL (see vtab.test as an example).
To check which extensions are available in TCL, or to add a new one, refer to the tester.tcl file and look at the extension_map.