When multicast is used with aggregration-strategy and shareUnitOfWork than junit test-cases are not able to pass. While if shareUnitOfWork is not used than all test pass.
Output observed when using shareUnitOfWork is:

The failures superficially appear to indicate that:
a) there is an extra call to aggregate adding a duplicate of the first result, see testShared_Grouped
b) onCompletion gets called twice, see testShared_Instrumented
c) the duplicate onCompletion calls probably explain the failure of testShared_Simple (given how AbstractListAggregationStrategy is implemented)

See the attached JUnit test case:
a) all the testUnshared_* cases pass
b) all the testShared_* cases unexpectedly fail