Preparations

1. in IDE:
   1. open the modules/custom/units/widgets/widget_eh.php file for editing
   2. in the \WidgetEventHandler::SetCustomQuery method after calling the parent method add $b = $a + 1;
   3. save changes

Part 1 (install/upgrade)

1. perform a clean install
2. login to the Admin Console
3. go to the Configuration → Website → Adanced section
4. confirm, that the Record code fragments in "System Log" for these paths (regexp) system setting is present and has #(modules/custom|system/cache/modules/custom)/.*# value
5. go to the Configuration → Website → Scheduled Tasks
6. confirm, that a rotate_system_log_code_fragments was added
7. go to phpMyAdmin
8. confirm, that TIMESTAMP_CODE_FRAGMENTS_ROTATED index for the SystemLog table is present

Part 2 (code fragment logging, filtering, display, rotation)

1. login to the Admin Console
2. go to the Configuration → Website → Adanced section
3. set the Record code fragments in "System Log" for these paths (regexp) system setting to (choose value based on test iteration):
   • #(modules/custom|system/cache/modules/custom)/.*#
   • #(core|system/cache/core)/.*#
   • (empty string)
4. save changes
5. go to the Custom → Widgets section
6. confirm, that an Undefined variable: a notice appears in Debugger
7. go to the Logs & Reports → System Log section
8. confirm, that record for the Undefined variable: a notice was created
9. open the record for the Undefined variable: a notice for viewing/editing
10. testing source line toggle code
    1. confirm, that the Toggle Code... link is shown at the end of the Source Filename: line value when a source file matches used filtering regexp
    2. click on the Toggle Code... link once
    3. confirm, that:
       • a highlighted code fragment appears
       • each line in the code fragment has a line number, that corresponds to the line number in the associated file
       • line number associated with the trace is marked with the >>> sign
11. testing backtrace
    1. confirm, that the backtrace looks visually the same as in other system log records
    2. click on the ALL Function: links of the backtrace records
    3. confirm, that:
       • the Arguments: text is shown above function/method arguments
       • the Toggle Code... link is shown below function/method arguments in the lines related to:
         • the Custom module files (e.g. PHP files from "modules/custom/units" or TPL file from the "modules/custom/admin_templates", that were compiled into PHP files), when the system setting was #(modules/custom|system/cache/modules/custom)/.*#
         • the Core module files (e.g. PHP files from "core/*" or TPL file from the "core/admin_templates", that were compiled into PHP files), when the system setting was #(core|system/cache/core)/.*#
         • the Core and Custom module files, when the system setting was (empty string)
    4. click on the Toggle Code... link once
    5. confirm, that:
       • a highlighted code fragment appears
       • each line in the code fragment has a line number, that corresponds to the line number in the associated file
       • line number associated with the trace is marked with the >>> sign
12. testing rotation
    1. execute the rotate_system_log_code_fragments scheduled task
    2. confirm, that system log records, created during tests, have retained their code fragments
    3. change the LogTimestamp of a system log record, that has code fragments to a 1672524000 (1 Jan 2023)
    4. execute the rotate_system_log_code_fragments scheduled task
    5. confirm, that above changed system log record doesn't contain any code fragments (source & backtrace)