How can I satisfy "#if canImport" in Swift macro unit tests?

Question

I'm trying out the macro support in Swift 5.9. I created a new macro package using:

swift package init --type macro

And in the example, unit tests come with:

    func testMacro() throws {
        #if canImport(SelfNamedMacros)
        assertMacroExpansion(
            """
            #stringify(a + b)
            """,
            expandedSource: """
            (a + b, "a + b")
            """,
            macros: testMacros
        )
        #else
        throw XCTSkip("macros are only supported when running tests for the host platform")
        #endif
    }

But I can't see actually how to make #if canImport(SelfNamedMacros) true and run the example test (my new macro package, i.e., the package directory, was named "SelfNamed"). That is, when I run the test, it always uses the XCTSkip path.

---

When I select:

I get the issue I had. I.e., "canImport" is false.

When I select:

The tests run as expected.