If this goes into 1.6 it should be mentioned in the release notes. Some tests might help avoid accidental changes in the future, although that might also depend on the order in which tests are executes.

Tests should also be careful to reset the state, so testing should be straightforward. Something like:

def test_default_fpe():
    err = np.geterr()
    assert_(err['over'] == 'warn')
    assert_(err['divide'] == 'warn')
    assert_(err['invalid'] == 'warn')
    assert_(err['under'] == 'ignore')

Added.

Merged.