You could use 
```
                assert_less(total_weight * est.min_weight_fraction_leaf,
                            np.min(leaf_weights) +
                            np.finfo(leaf_weights.dtype).eps,
                            "Failed with {0} "
                            "min_weight_fraction_leaf={1}".format(
                                name, est.min_weight_fraction_leaf))
```
or
```
                assert_greater(np.min(leaf_weights) +
                               np.finfo(leaf_weights.dtype).eps,
                               total_weight * est.min_weight_fraction_leaf,
                               "Failed with {0} min_weight_fraction_leaf={1} "
                               "".format( name, est.min_weight_fraction_leaf))

```