Project with Swift Package dependencies results in "Unexpected duplicate tasks" error

I've been trying to convert a set of app and library projects to use swift packages for dependencies (previously used Carthage), and I've run into an issue where Xcode is throwing me a diagnostic for "Unexpected duplicate tasks".

The setup:

• A dynamic library package which includes some file resources (not any special resources like asset catalogs or CoreData models). Let's call this LibA.

• A second dynamic library, containing test utilities, which depends on LibA. Let's call this one LibB.

• An iOS app project, where the app target depends on LibA, and the unit test target depends on LibB, and transitively through LibB, depends on LibA.

The result is Xcode will compile the app target, but when compiling the unit test target, fails with the diagnostic:

Code Block 
Unexpected duplicate tasks:
1) Target 'TestPMAppTests' (project 'TestPMApp') has copy command from '/Users/someone/Library/Developer/Xcode/DerivedData/TestPMApp-bsobwbvrasoqbtejzhodakcdkqqu/Build/Products/Debug-iphonesimulator/liba_liba.bundle' to '/Users/someone/Library/Developer/Xcode/DerivedData/TestPMApp-bsobwbvrasoqbtejzhodakcdkqqu/Build/Products/Debug-iphonesimulator/TestPMApp.app/PlugIns/TestPMAppTests.xctest/liba_liba.bundle'
2) Target 'TestPMAppTests' (project 'TestPMApp') has copy command from '/Users/someone/Library/Developer/Xcode/DerivedData/TestPMApp-bsobwbvrasoqbtejzhodakcdkqqu/Build/Products/Debug-iphonesimulator/liba_liba.bundle' to '/Users/someone/Library/Developer/Xcode/DerivedData/TestPMApp-bsobwbvrasoqbtejzhodakcdkqqu/Build/Products/Debug-iphonesimulator/TestPMApp.app/PlugIns/TestPMAppTests.xctest/liba_liba.bundle'

Is this something that is expected behaviour here?