lib.py

def myadd(a, b):
    print("Now when we drop into pdb, backspace will not work")
    
    import pdb
    pdb.set_trace()
    return a + b

requirements.txt

invoke==0.22.1
nose==1.3.7

tasks.py

from invoke import task

@task

def test(ctx, pty=True):    
    """ Run a unit test """

    cmd = "nosetests --nocapture" 
    print(cmd)
    ctx.run(cmd)
    

test.py

from lib import myadd

def test_myadd():
    assert myadd(1,1) == 2