To reproduce, create the following three files:

testit.go

    package testit

extern_test.go:

    package testit_test

    import (
        "code.google.com/p/rog-go/testit"
    )

    func init() {
        testit.Register()
        unused
    }

intern_test.go:

    package testit
    
    import "testing"
    
    var registered bool
    
    func Register() {
        registered = true
    }
    
    func TestPackage(t *testing.T) {
        if !registered {
            t.Fatal("registry never called")
        }
    }

Running the tests gives the error "registry never called",
indicating that the code in extern_test.go is never run.
Moreover, it's not even compiled - there's no error from
the unused variable.

While it may look contrived, the above configuration mirrors the way
that tests are registered with the popular gocheck testing
package - tests that were previously run correctly may now
be silently skipped.

I have verified that this is a regression since Go 1.2.2.

FWIW, there is an easy workaround (define TestPackage in the external
test file) but it might be better to avoid the regression.