Part of #1971384: [META] Convert page callbacks to controllers
For instructions on how to convert a page callback into a controller, see the WSCCI Conversion Guide.
Need to rewrite the whole module to make test sync with current test implementation. For more details, please refer: #1988802: [META] Rewrite test modules in system to provide better unit testing.
I'll take this one.
See #1987624: Convert batch_test page callbacks to a new style controller which covers all callbacks for the batch_test module.
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