var (
	swigOnce sync.Once
	haveSwig bool
)

func mustHaveSwig(t *testing.T) {
	swigOnce.Do(func() {
		mustHaveSwigOnce(t)
		haveSwig = true
	})
	// The first call will skip t with a nice message. On later calls, we just skip.
	if !haveSwig {
		t.Skip("swig not found")
	}
}

func mustHaveSwigOnce(t *testing.T) {
	swig, err := exec.LookPath("swig")
	if err != nil {
		t.Skipf("swig not in PATH: %s", err)
	}