"Run as > JUnit Test" on a Java Package also launches Tests of sibling packages with same prefix

Suppose the following package structure:

Then, performing "Run as > JUnit Test" on the `com.example.a` package will also run all Tests inside the `com.example.ab` package. This behaviour deviates from how the packages are displayed in eclipse (In both "flat" and "hierarchical" Presentation modes)

Because of this package presentation, users expect that only the tests in the `com.example.a` package (and any nested packages) are executed.
However, the Tests in the `com.example.ab` package are also executed:

Reproduce the "Run as > JUnit Test" action on the `com.example.a` package with the shown sibling `com.example.ab` package. Start by tracing the package-selection entry point for this launch action and compare the packages selected with the tests actually run. Done means selecting `com.example.a` runs its tests and nested packages without also running `com.example.ab`.

Written by the indexing model from the issue text.