<s>
In	O
computer	B-General_Concept
programming	I-General_Concept
,	O
a	O
characterization	B-General_Concept
test	I-General_Concept
(	O
also	O
known	O
as	O
Golden	B-General_Concept
Master	I-General_Concept
Testing	I-General_Concept
)	O
is	O
a	O
means	O
to	O
describe	O
(	O
characterize	O
)	O
the	O
actual	O
behavior	O
of	O
an	O
existing	O
piece	O
of	O
software	O
,	O
and	O
therefore	O
protect	O
existing	O
behavior	O
of	O
legacy	B-Device
code	I-Device
against	O
unintended	O
changes	O
via	O
automated	B-Application
testing	I-Application
.	O
</s>
<s>
The	O
goal	O
of	O
characterization	B-General_Concept
tests	I-General_Concept
is	O
to	O
help	O
developers	O
verify	O
that	O
the	O
modifications	O
made	O
to	O
a	O
reference	O
version	O
of	O
a	O
software	O
system	O
did	O
not	O
modify	O
its	O
behavior	O
in	O
unwanted	O
or	O
undesirable	O
ways	O
.	O
</s>
<s>
In	O
James	O
Bach	O
's	O
and	O
Michael	O
Bolton	O
's	O
classification	O
of	O
test	O
oracles	O
,	O
this	O
kind	O
of	O
testing	O
corresponds	O
to	O
the	O
historical	B-General_Concept
oracle	I-General_Concept
.	O
</s>
<s>
When	O
creating	O
a	O
characterization	B-General_Concept
test	I-General_Concept
,	O
one	O
must	O
observe	O
what	O
outputs	O
occur	O
for	O
a	O
given	O
set	O
of	O
inputs	O
.	O
</s>
<s>
Given	O
an	O
observation	O
that	O
the	O
legacy	B-Device
code	I-Device
gives	O
a	O
certain	O
output	O
based	O
on	O
given	O
inputs	O
,	O
then	O
a	O
test	O
can	O
be	O
written	O
that	O
asserts	O
that	O
the	O
output	O
of	O
the	O
legacy	B-Device
code	I-Device
matches	O
the	O
observed	O
result	O
for	O
the	O
given	O
inputs	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
one	O
observes	O
that	O
f( 	O
3.14	O
)	O
==	O
42	O
,	O
then	O
this	O
could	O
be	O
created	O
as	O
a	O
characterization	B-General_Concept
test	I-General_Concept
.	O
</s>
<s>
Unfortunately	O
,	O
as	O
with	O
any	O
testing	O
,	O
it	O
is	O
generally	O
not	O
possible	O
to	O
create	O
a	O
characterization	B-General_Concept
test	I-General_Concept
for	O
every	O
possible	O
input	O
and	O
output	O
.	O
</s>
<s>
It	O
is	O
often	O
sufficient	O
to	O
write	O
characterization	B-General_Concept
tests	I-General_Concept
that	O
only	O
cover	O
the	O
specific	O
inputs	O
and	O
outputs	O
that	O
are	O
known	O
to	O
occur	O
,	O
paying	O
special	O
attention	O
to	O
edge	O
cases	O
.	O
</s>
<s>
Unlike	O
regression	O
tests	O
,	O
to	O
which	O
they	O
are	O
very	O
similar	O
,	O
characterization	B-General_Concept
tests	I-General_Concept
do	O
not	O
verify	O
the	O
correct	O
behavior	O
of	O
the	O
code	O
,	O
which	O
can	O
be	O
impossible	O
to	O
determine	O
.	O
</s>
<s>
Often	O
no	O
specification	O
or	O
test	O
suite	O
is	O
available	O
,	O
leaving	O
only	O
characterization	B-General_Concept
tests	I-General_Concept
as	O
an	O
option	O
,	O
since	O
the	O
conservative	O
path	O
is	O
to	O
assume	O
that	O
the	O
old	O
behavior	O
is	O
the	O
required	O
behavior	O
.	O
</s>
<s>
Characterization	B-General_Concept
tests	I-General_Concept
are	O
,	O
essentially	O
,	O
change	O
detectors	O
.	O
</s>
<s>
One	O
of	O
the	O
interesting	O
aspects	O
of	O
characterization	B-General_Concept
tests	I-General_Concept
is	O
that	O
,	O
since	O
they	O
are	O
based	O
on	O
existing	O
code	O
,	O
it	O
's	O
possible	O
to	O
generate	O
some	O
characterization	B-General_Concept
tests	I-General_Concept
automatically	O
.	O
</s>
<s>
An	O
automated	O
characterization	B-General_Concept
test	I-General_Concept
tool	O
will	O
exercise	O
existing	O
code	O
with	O
a	O
wide	O
range	O
of	O
relevant	O
and/or	O
random	O
input	O
values	O
,	O
record	O
the	O
output	O
values	O
(	O
or	O
state	O
changes	O
)	O
and	O
generate	O
a	O
set	O
of	O
characterization	B-General_Concept
tests	I-General_Concept
.	O
</s>
<s>
When	O
testing	O
on	O
the	O
GUI	B-Application
level	O
,	O
characterization	O
testing	O
can	O
be	O
combined	O
with	O
intelligent	O
monkey	O
testing	O
to	O
create	O
complex	O
test	O
cases	O
that	O
capture	O
use	O
cases	O
and	O
special	O
cases	O
thereof	O
.	O
</s>
<s>
Golden	B-General_Concept
Master	I-General_Concept
testing	I-General_Concept
has	O
the	O
following	O
advantages	O
over	O
the	O
traditional	O
assertions-based	O
software	O
testing	O
:	O
</s>
<s>
It	O
is	O
relatively	O
easy	O
to	O
implement	O
for	O
complex	O
legacy	B-Device
systems	I-Device
.	O
</s>
<s>
It	O
is	O
generally	O
a	O
sensible	O
approach	O
for	O
complex	O
results	O
such	O
as	O
PDFs	B-Application
,	O
XML	B-Protocol
,	O
images	O
,	O
etc	O
.	O
</s>
<s>
Golden	B-General_Concept
Master	I-General_Concept
testing	I-General_Concept
has	O
the	O
following	O
disadvantages	O
over	O
traditional	O
assertions-based	O
software	O
testing	O
:	O
</s>
<s>
If	O
too	O
many	O
elements	O
need	O
to	O
be	O
removed	O
or	O
removing	O
them	O
is	O
too	O
complex	O
,	O
it	O
can	O
render	O
Golden	B-General_Concept
Master	I-General_Concept
testing	I-General_Concept
impractical	O
.	O
</s>
<s>
Golden	B-General_Concept
Master	I-General_Concept
testing	I-General_Concept
does	O
not	O
infer	O
correctness	O
of	O
the	O
results	O
.	O
</s>
