coverage.py exec

impl.py

def foo():
    print "foo"

def bar():
    print "bar"

impl2.py

print "the answer to life, the universe and everything is: {}".format(undeclared_var)

test.py

from impl import foo

foo()

namespace = {
    'undeclared_var': 42
}

with open('impl2.py') as f:
    code = compile(f.read(), 'impl2.py', 'exec')
    exec(code, globals(), namespace)

$ coverage run --source . test.py
foo
the answer to life, the universe and everything is: 42

$ coverage report
Name    Stmts   Miss  Cover
---------------------------
impl        4      1    75%
impl2       1      1     0%
test        6      0   100%
---------------------------
TOTAL      11      2    82%