SwiftPM Tests Undefined Symbol Working with C++ Dependency

Using Swift
1

I've created a swift package that has multiple targets. For example:

.target(
    name: "LibrarySwift",
    dependencies: [
        "LibraryObjC"]),
.target(
    name: "LibraryObjC",
    dependencies: ["LibraryCPP"],
    cxxSettings: [
        .headerSearchPath("../../LibraryCPP/")]),
.target(
     name: "LibraryCPP",
     cxxSettings: [
         .headerSearchPath("../../LibraryCPP/")]),
.testTarget(
    name: "LibrarySwiftTests",
    dependencies: ["LibrarySwift"]),

With the test target commented out, everything builds as expected, I can call the Objective-C functions that wrap the C++ library functions within LibrarySwift, etc. However, when I enable the test target that uses LibrarySwift I suddenly get a bunch of Undefined Symbol warnings in the test target for LibraryCPP objects.

Searching around I've found a couple of similar issues where the problem was SwiftPM considering a main.swift file as an executable. The resolution was to remove or package that main.swift separately allowing the source to be treated as a library. But I'm not sure how to approach and troubleshoot this with a C++ library and if it's a related or entirely different issue.

Edit: I was able to verify this same issue also happens while importing the LibrarySwift into an example project (e.g. iOS)