<s>
Software	B-Application
testability	I-Application
is	O
the	O
degree	O
to	O
which	O
a	O
software	O
artifact	O
(	O
i.e.	O
</s>
<s>
A	O
lower	O
degree	O
of	O
testability	O
results	O
in	O
increased	O
test	B-Application
effort	I-Application
.	O
</s>
<s>
In	O
extreme	O
cases	O
a	O
lack	O
of	O
testability	O
may	O
hinder	O
testing	O
parts	O
of	O
the	O
software	O
or	O
software	B-General_Concept
requirements	I-General_Concept
at	O
all	O
.	O
</s>
<s>
For	O
instance	O
,	O
testing	O
when	O
we	O
assume	O
that	O
the	O
behavior	O
of	O
the	O
implementation	O
under	O
test	O
can	O
be	O
denoted	O
by	O
a	O
deterministic	O
finite-state	B-Architecture
machine	I-Architecture
for	O
some	O
known	O
finite	O
sets	O
of	O
inputs	O
and	O
outputs	O
and	O
with	O
some	O
known	O
number	O
of	O
states	O
belongs	O
to	O
Class	O
I	O
(	O
and	O
all	O
subsequent	O
classes	O
)	O
.	O
</s>
<s>
If	O
the	O
implementation	O
under	O
test	O
must	O
be	O
a	O
deterministic	O
finite-state	B-Architecture
machine	I-Architecture
failing	O
the	O
specification	O
for	O
a	O
single	O
trace	O
(	O
and	O
its	O
continuations	O
)	O
,	O
and	O
its	O
number	O
of	O
states	O
is	O
unknown	O
,	O
then	O
it	O
only	O
belongs	O
to	O
classes	O
from	O
Class	O
III	O
on	O
.	O
</s>
