a1/2approach.tex

   1 The test process consists of several stages. The results of the first stage,
   2 planning, are descibed in this document. On the basis of this document actual
   3 test cases will be designed. Afterwards the actual tests will be implemented
   4 and executed. The results of these tests will then be evaluated against the
   5 exit criteria found in Section~\ref{sec:exitcriteria} and depending on the
   6 outcome of these evaluations further tests might be deemed necessary.
   7
   8 \subsection{Quality Characteristics}
   9 The quality characteristics that are to be tested are described using the
  10 ISO/IEC 25010~\cite{iso25010} as a guideline. In the following sections we will
  11 discuss the relevant \textit{product quality} and \textit{quality in use}
  12 characteristics.
  13
  14 \subsubsection{Product quality}
  15 Product quality is divided into eight main categories which are divided into
  16 several subcategories. Below we will discuss the qualities which are relevant
  17 to the SUT.
  18 \begin{itemize}
  19         \item \textbf{Functional suitability}\\
  20         As described in Section~\ref{sec:risks} the SUT is core functionality of
  21         the networking capable system. Because many other systems running on the
  22         system could rely on it it is very important that the SUT is functionality
  23         suitable. Therefore all three sub characteristics of Functional
  24         Suitability (\textit{Functional completeness, Functional correctness,
  25         Functional appropriateness}) are of vital importance. As was previously
  26         mentioned in Section~\ref{sec:risks} extra emphasis should be placed on
  27         testing \emph{Functional Correctness} as recovery from Failures in
  28         computer-to-computer systems is problematic.
  29         \item \textbf{Performance efficiency} \label{sec:perf_eff}\\
  30         As the SUT runs as a service on a system with other programs it must have
  31         efficient \emph{resource utilisation}. It can not contain any memory leaks
  32         or use other resources more than necessary.
  33         \item \textbf{Compatibility}\\
  34         \emph{Interoperability} is the key feature of the SUT as it's purpose is to
  35         communicate with other systems implementing the TCP protocol. Therefore it
  36         is of vital importance that the SUT implements the TCP protocol correctly.
  37         Furthermore it is very important that the SUT can \emph{co-exist} with
  38         other programs on the system it runs on, since it is used as a service by
  39         those programs. This means that the SUT has to handle preemption as well as
  40         having multiple programs requesting it's services at once.
  41         \item \textbf{Reliability}\\
  42         As stated before, the SUT is used as a core service, this means it has to
  43         be very \emph{mature}. It needs to behave as expected under normal working
  44         conditions. As it can continually be requested the SUT needs to have
  45         constant
  46         \emph{availability}. As the SUT relies on a potentially unreliable channel
  47         to send and receive data it needs to be \emph{fault tolerant}. The SUT
  48         needs to properly handle errors in received data or complete unavailability
  49         of the underlying channel.
  50 \end{itemize}
  51 This leaves four categories which are not relevant the SUT. Below we will
  52 shortly discuss per category why these are not relevant. \emph{Maintainability}
  53 is an important aspect of any software system, however for the SUT it is not a
  54 core aspect, as it is first and foremost of importance that the implementation
  55 is correct, furthermore TCP does not change often. \emph{Usability} isn't a
  56 core aspect either, as the SUT is not used directly by humans, but is a service
  57 which is addressed when another program needs it. \emph{Portability} isn't
  58 either as the SUT is installed on a system once and intended to work on that
  59 system. \emph{Security} isn't a feature of the SUT either, systems using the
  60 SUT can add their own security mechanisms on top of it.
  61
  62
  63 \subsubsection{Quality in use}
  64 Quality in use is dived into five subcategories. Below we will discuss the
  65 categories which are relevant to the SUT.
  66 \begin{itemize}
  67         \item \textbf{Effectiveness}\\
  68         This is the core aspect of the SUT, users (other programs) need to be able
  69         to effectively use the SUT to send and receive data.
  70         \item \textbf{Efficiency}\\
  71         This issue has already been covered above under
  72         ``performance efficiency''~\ref{sec:perf_eff}.
  73         \item \textbf{Satisfaction}\\
  74         It is important that programs using the SUT can \emph{trust} that the SUT
  75         provides the promised services. This means that data is send and received
  76         reliably and the SUT provides clear and unambiguous errors when this
  77         service
  78         can not be provided.
  79         \item \textbf{Context Coverage}\\
  80         The SUT needs to behave as expected in all specified contexts
  81         (\emph{context completeness}).
  82 \end{itemize}
  83 This leaves \emph{freedom from risk}, which we consider not relevant as the SUT
  84 itself does not pose any risks, and correct implementation (which is covered in
  85 the other categories) gives clear guarantees to programs using the services of
  86 the SUT.
  87
  88 \subsection{Levels and types of testing} \label{section:levels}
  89 The client will deliver a product for certification. This means our team will
  90 only conduct \emph{acceptance testing} and assume that the client who requested
  91 certification has conducted \emph{unit}, \emph{module} and \emph{integration
  92 testing}. We will only be conducting \emph{black-box testing} and the client
  93 is not required to handover any source-code.
  94
  95 Initially we will conduct a few basic \emph{manual tests} based on experience
  96 acquired from previous certification requests (\emph{error guessing}). If the
  97 product fails these basic tests we immediately reject it and seize all further
  98 activities.
  99
 100 If the product is not rejected after the basic \emph{manual tests} we will
 101 proceed with the second stage of testing. For these follow-up tests we will use
 102 \emph{equivalence partitioning} to reduce the number of test cases. Every test
 103 case will result in a test report. If any of the test cases fail the product
 104 is rejected. In order to deliver usable feedback to the client we will still
 105 produce a test report.
 106
 107 \subsubsection{Manual tests}
 108
 109 The basic tests mentioned in Section~\ref{section:levels} are conducted using a
 110 checklist. If any of the checks fail we immediately reject the product.
 111
 112 \begin{enumerate}
 113         \item Is the product complete?
 114         \item Does the product come with a manual or quick start guide?
 115         \item Is it possible to get the product in a usable state?
 116         \item Can we use the product to initiate a connection in a corruption
 117         free
 118         environment?
 119 \end{enumerate}
 120
 121 These\emph{ manual tests} are performed in order to ensure that the client has
 122 delivered a usable product.
 123
 124 \subsubsection{Test generation}
 125
 126 For the second state of testing we first use \emph{equivalence partitioning} to
 127 reduce the overall number of test cases as mentioned in
 128 Section~\ref{section:levels}. At the highest level we can define the following
 129 equivalent \emph{input classes} for the SUT.
 130
 131 \begin{enumerate}
 132         \item Valid requests:
 133                 \begin{enumerate}
 134                         \item Single request.
 135                         \item Multiple requests.
 136                 \end{enumerate}
 137         \item Invalid requests:
 138                 \begin{enumerate}
 139                         \item Single request.
 140                         \item Multiple requests.
 141                 \end{enumerate}
 142 \end{enumerate}
 143
 144 For these requests we can introduce more cases by applying \emph{equivalence
 145 partitioning} to the different packets that are sent during one request.
 146
 147 \begin{enumerate}
 148         \item Packets received in order.
 149         \item Packets received out of order.
 150 \end{enumerate}
 151
 152 For each individual packet we can specify the follow \emph{equivalent classes}.
 153
 154 \begin{enumerate}
 155         \item Valid packet.
 156         \item Corrupted packet.
 157         \item Missing packets.
 158 \end{enumerate}
 159
 160 A \emph{decision table} is used in order to ensure all different equivalent
 161 classes are covered in our tests. Valid packets can only exist in one form,
 162 the valid form and there is no need to divide these into additional classes.
 163 For the invalid packets we will construct a test case where only one parameter
 164 is made invalid. For the invalid value of this parameter we use \emph{boundary
 165 value analysis} to reduce the total number of test cases. The SUT input
 166 parameters correspond to different fields in the network packets. The
 167 following fields and there boundary values are considered during the testing.
 168
 169 \begin{enumerate}
 170         \item Checksum: valid, invalid.
 171         \item Header: valid, even or odd number of bits corrupted.
 172         \item Payload: valid, even or odd number of bits corrupted.
 173 \end{enumerate}
 174
 175 \subsubsection{Test environment and automatization}
 176 \label{section:testenv}
 177 All the tools we are going to use together with the SUT gives us the following
 178 collection of software
 179
 180 \begin{itemize}
 181         \item Windows\footnote{\url{http://www.microsoft.com/en-us/windows}}, used
 182                         as a host OS.
 183         \item Ubuntu\footnote{\url{http://www.ubuntu.com}}, used as the guest OS
 184                         running the SUT.
 185         \item VirtualBox\footnote{\url{https://www.virtualbox.org/}}, used to run
 186                         the guest OS containing the SUT.
 187         \item Wireshark\footnote{\url{https://www.wireshark.org/}}, used on the
 188                         guest OS in order to capture and analyze network traffic.
 189         \item Bit-Twist\footnote{\url{http://bittwist.sourceforge.net/}}, used to
 190                         prepare network packets.
 191         \item Java\footnote{\url{http://www.java.com}} TCP driven echo server.
 192 \end{itemize}
 193
 194 \begin{figure}[H]
 195                 \label{fig:sut}
 196                 \centering
 197                 \includegraphics[width=0.5\linewidth]{SUTsetup.eps}
 198                 \caption{Test environment}
 199 \end{figure}
 200
 201
 202 All test will be conducted in a virtual environment. We will use VirtualBox to
 203 run a Linux distribution with the product installed. The Linux distribution in
 204 question is Ubuntu. All the tests are performed from within the VirtualBox
 205 environment. When testing network transmissions we will only analyze the
 206 packets sent/received to/from the SUT. The host system is disconnected from the
 207 Internet or any other network in order to prevent unnecessary traffic.
 208 % Dit is niet nodig omdat het via loopback gaat
 209 %       Zeker weten? de SUT ontvangt ook niet loopback packets toch?
 210 %               Ja maar we geven de host gewoon geen interface?
 211
 212 For each test case (except for the \emph{manual tests}) a file containing
 213 previously captured network traffic will be replayed using Wireshark and sent
 214 to the \emph{Java TCP driven echo server}. We will use Bit-Twist to update the
 215 prepared packets with the MAC address of the guest network adapter and provide
 216 them with a valid source address. This updating step is needed because the
 217 kernel would otherwise reject the packets and prevent them from reaching the
 218 SUT. The response packets sent by the \emph{Java TCP driven echo server} and
 219 passing trough the SUT will be recorded, analyzed and validated according to
 220 the \textit{RFC793} specification. The valid packets are build manually from
 221 the \textit{RFC793} specification. Invalid packets are generated from this
 222 valid traffic using Bit-Twist. The boundary values for the different
 223 parameters (fields in packets) are determined by hand. Automated scripts are
 224 used in order to generate packets with some fields replaced with these
 225 \emph{boundary values}.