(t *testing.T) {  b, tmpPath := backend.NewDefaultTmpBackend()  s := NewStore(b, &lease.FakeLessor{}, nil)  defer cleanup(s, b, tmpPath)   s.Put([]byte("foo"), []byte("bar0"), lease.NoLease)  s.Put([]byte("foo"), []byte("bar0"), lease.NoLease)  s.Put([]byte("foo"), []byte("bar0"), lease.NoLease)   // rev in tests will be called in Compact() one by one on the same store  tests := []struct {   rev  int00   werr error  }{   {