In my test branch I have inserted the following lines to avoid out of control search trees:
```
      if (all_nodes.size() > 10000000) {
              std::cerr << "all_nodes.size() " << all_nodes.size() <<
                      " open.size() " << open.size() << std::endl;
              break;
      }
```

The cutoff here is ten million. When I tried one million the unit tests broke due to different alignments being found.

The ecoli_rand_error dataset has six reads whose ideal alignment (trusted coverage = 1) exceeds this threshold. Over 200 reads and counting exceed this threshold when the trusted coverage cutoff is 5.