Previously, create_angular_testing_module would export a mutable `let`
binding. The binding is already exporting using an accessor function
though, so the export on the let variable seems like an accidental
oversight.
This is functionally equivalent, but makes it easier for module
optimizers such as Closure Compiler to track down side effects and prune
modules.
PR Close#34232
Adds two new helper functions that can be used when unit testing Angular services
that depend upon upgraded AngularJS services, or vice versa.
The functions return a module (AngularJS or NgModule) that is configured to wire up
the Angular and AngularJS injectors without the need to actually bootstrap a full
hybrid application.
This makes it simpler and faster to unit test services.
PR Close#16848
