Testing for the binding loops requires a second instance of the TestedClass. In general case, we cannot guarantee that the TestedClass is default-constructible, so we introduce a new parameter - a function that returns an std::unique_ptr holding the properly-constructed instance of TestedClass. The default implementation simply creates a unique_ptr using a default constructor, which is good enough for most cases. The user needs to provide a custom function when TestedClass has no default constructor (for now such usecase exists at least in QtScxml and QtPositioning). This patch introduces new signatures for the helper functions, but does not actually provide new implementation. This is an attempt to simplify the CI integration process. The new arguments have default values, so the existing code will not be affected. The idea is that the merge process goes as follows: * this patch gets merged into qtbase. It should not break leaf modules, because the new parameters have default values -> existing tests are unaffected. * it unblocks all patches to the leaf modules that require the new parameter for the test helper functions. These patches are also supposed to fix all the problems with the binding loops. * once these patches are merged, a follow-up patch to qtbase that actually extends the test coverage can be merged. As it is supposed that all problems in the leaf modules are already fixed, merging this patch should not lead to new problems. The actual implementation of the new tests is provided in a follow-up patch. Task-number: QTBUG-116345 Pick-to: 6.6 6.5 Change-Id: I0dd5c8c60de01aa960d63673b5d7de97950d9490 Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>