When using test/Project.toml the dependencies from the main package are no longer available via import/using #101
Description
By chance I stumbled upon the different behaviour of [extras]/[targets] and having a separate test/Project.toml.
Concretely, I cannot import a dependency from the main package, say using Distances inside a @testitem if it is not explicitly add to test/Project.toml.
When using the [extras]/[targets] way of defining test dependencies, all dependencies from the main package are available as well.