comprehensive test coverage

Ensure test suites provide comprehensive coverage by including edge cases, boundary conditions, and input variations while verifying that tests actually validate the intended functionality. Tests should cover different input formats (case sensitivity, precision levels), boundary values (empty inputs, maximum/minimum values), and error conditions. Remove test cases that don’t actually test the target functionality.

Example of comprehensive testing:

-- Test different case variations
SELECT time_trunc('HOUR', time'12:34:56');
SELECT time_trunc('hour', time'12:34:56');
SELECT time_trunc('Hour', time'12:34:56');

-- Test boundary conditions
SELECT split('', '', -1);
SELECT split('', '', 0);
SELECT split('', '', 1);

-- Test different precisions
SELECT time_trunc('MICROSECOND', time'12:34:56.123456');
SELECT time_trunc('MICROSECOND', time'12:34:56.123456789');

This approach ensures robust validation of functionality across all realistic usage scenarios and prevents regressions from unexpected input combinations.