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Test methods voorbeeld

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Joshua Moerman 2018-12-21 14:04:03 +01:00
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65
content/introduction.tex
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@ -229,16 +229,16 @@ More background and other related problems, as well as their complexity results,
In the following example we model a record player as a finite state machine. In the following example we model a record player as a finite state machine.
We will not model the audible output -- that would depend not only on the device, but also the record one chooses to play. We will not model the audible output -- that would depend not only on the device, but also the record one chooses to play.
Instead, we the only observation we can make is seeing how fast the turntable spins. Instead, the only observation we can make is looking how fast the turntable spins.
The device has two buttons: a start-stop button (\playstop) and a speed toggle (\spin) which chooses between $33 \frac{1}{3}$ rpm and $45$ rpm. The device has two buttons: a start-stop button (\playstop) and a speed button (\spin) which toggles between $33 \frac{1}{3}$ rpm and $45$ rpm.
When turned on, the system should start playing immediately at $33 \frac{1}{3}$ rpm -- this is useful for DJing. When turned on, the system starts playing immediately at $33 \frac{1}{3}$ rpm -- this is useful for DJing.
The system has four states as depicted in \in{Figure}[fig:record-player]. The intended behaviour of the records player has four states as depicted in \in{Figure}[fig:record-player].
\startplacefigure \startplacefigure
[title={Behaviour of a record player modelled as a finite state machine.}, [title={Behaviour of a record player modelled as a finite state machine.},
reference=fig:record-player] reference=fig:record-player]
\hbox{\starttikzpicture[node distance=4cm, bend angle=10] \hbox{\starttikzpicture[node distance=4cm, bend angle=10]
\node[state, initial, align=center] (tl) {slow\\spinning}; \node[state, initial above, align=center] (tl) {slow\\spinning};
\node[state, right of=tl, align=center] (tr) {fast\\spinning}; \node[state, right of=tl, align=center] (tr) {fast\\spinning};
\node[state, below of=tl, align=center] (bl) {no\\spinning}; \node[state, below of=tl, align=center] (bl) {no\\spinning};
\node[state, right of=bl, align=center] (br) {no\\spinning}; \node[state, right of=bl, align=center] (br) {no\\spinning};
@ -255,7 +255,60 @@ The system has four states as depicted in \in{Figure}[fig:record-player].
\stoptikzpicture} \stoptikzpicture}
\stopplacefigure \stopplacefigure
\todo{I want to give an example (by giving a state machine) of why black box testing is hard.} Let us consider some faults which could be present in an implementation with four states.
In \in{Figure}[fig:faulty-record-players] two flawed records players are given.
In the first (\in{Figure}{a}[fig:faulty-record-players]) the sequence \playstop\,\spin\,\spin\, leads us to the wrong state.
However, this is not immediately observable, the turntable is in a non-spinning state as it should be.
The fault is only visible when we press \playstop\, once more: now the turntable is spinning fast instead of slow.
The sequence \playstop\,\spin\,\spin\,\playstop\, is a counterexample.
In the second example (\in{Figure}{b}[fig:faulty-record-players]), the fault is again not immediately obvious: after pressing \spin\,\playstop\, we are in the wrong state as observably by pressing \playstop.
Here, the counterexample is \spin\,\playstop\,\playstop.
When a model of the implementation is given, it is not hard to find counterexamples.
However, in a black box setting we do not have such a model.
In order test whether a black box system is equivalent to a model, we somehow need to test all possible counterexamples.
In this example, a test suite should at least include the sequences \playstop\,\spin\,\spin\,\playstop\, and \spin\,\playstop\,\playstop.
\startplacefigure
[title={Two faulty record players.},
reference=fig:faulty-record-players]
\startcombination[nx=2, ny=1, location=top, distance=1.5cm]
{\hbox{\starttikzpicture[node distance=3cm, bend angle=10]
\node[state, initial above, align=center] (tl) {slow\\spinning};
\node[state, right of=tl, align=center] (tr) {fast\\spinning};
\node[state, below of=tl, align=center] (bl) {no\\spinning};
\node[state, right of=bl, align=center] (br) {no\\spinning};
\path[->]
(tl) edge [bend right] node [left] {\playstop} (bl)
(tl) edge [bend right] node [below] {\spin} (tr)
(bl) edge [bend right] node [right] {\playstop} (tl)
(bl) edge [bend right] node [below] {\spin} (br)
(tr) edge [bend right] node [above] {\spin} (tl)
(tr) edge [bend right] node [left] {\playstop} (br)
(br) edge [bend right] node [right] {\playstop} (tr)
(br) edge [loop below, color=red] node [above] {\spin} (br);
\stoptikzpicture}}{a}
{\hbox{\starttikzpicture[node distance=3cm, bend angle=10]
\node[state, initial above, align=center] (tl) {slow\\spinning};
\node[state, right of=tl, align=center] (tr) {fast\\spinning};
\node[state, below of=tl, align=center] (bl) {no\\spinning};
\node[state, right of=bl, align=center] (br) {no\\spinning};
\path[->]
(tl) edge [bend right] node [left] {\playstop} (bl)
(tl) edge [bend right] node [below] {\spin} (tr)
(bl) edge [bend right] node [right] {\playstop} (tl)
(bl) edge [bend right] node [below] {\spin} (br)
(tr) edge [bend right] node [above] {\spin} (tl)
(tr) edge [color=red] node [below right] {\playstop} (bl)
(br) edge [bend right] node [right] {\playstop} (tr)
(br) edge [bend right] node [above] {\spin} (bl);
\stoptikzpicture}}{b}
\stopcombination
\stopplacefigure
\todo{I want to move some related work from the second chapter to here}. \todo{I want to move some related work from the second chapter to here}.

2
environment/notation.tex
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@ -13,7 +13,7 @@
\define\bomb{\!\scale[height=.65em]{\symbol[fontawesome][]}} % bomb \define\bomb{\!\scale[height=.65em]{\symbol[fontawesome][]}} % bomb
\define\money{\scale[height=.6em]{\symbol[fontawesome][eur]}\,} % euro sign + space \define\money{\scale[height=.6em]{\symbol[fontawesome][eur]}\,} % euro sign + space
\define\playstop{\scale[height=.5em]{\symbol[fontawesome][play]}\scale[height=.5em]{\symbol[fontawesome][pause]}} % play / stop symbol \define\playstop{\scale[height=.5em]{\raise.15ex\hbox{\symbol[fontawesome][play]\symbol[fontawesome][pause]}}} % play / stop symbol
\define\spin{\scale[height=.6em]{\symbol[fontawesome][repeat]}} % spinning symbol \define\spin{\scale[height=.6em]{\symbol[fontawesome][repeat]}} % spinning symbol
%\define\spin{\kw{spd}} % spinning symbol %\define\spin{\kw{spd}} % spinning symbol