Ch. 14 System Testing (with new slides 4/18) Earlier we have stated the 2 views of testing: To show that the software works (according to specification) To detect as many defects (and have them fixed prior to releasing to the users) as possible In system testing we are more interested in showing that the system, as a whole with all the “major” specifications – especially cross-component, is working. Still Interested in knowing which “major” function is not working. (But this should be rare if we completed functional and component test properly.) We are not focused on all types of exception during systems test, but want to make sure that when multiple paths (threads) are executed, it still works according to the requirements. System testing is a blend of functional (black-box) and structural (white-box) testing - - - testing mostly “main” threads of system behavior. 4/11 PP1 Verification 4/13 PP1 Book says: ? System Testing

4/13 PP2 Define DD path; DU path; amd MM path. Threads A thread is a sequence of activities that are observable. There are many levels of granularity for a thread: A sequence of instructions as in a DU-path for unit test (DU is Define/Use Testing) A flow of control among a set of related modules as in a MM-path in an integration path. (MM is module-message or method-message) A sequence of “atomic” functions that contributes to the accomplishment of a major functionality as described in a requirements specification. In system testing, we are interested in the a) high-level (cross-functional) threads and b) “multiple” threads. 4/13 PP2 Define DD path; DU path; amd MM path. Threads A scenario of normal usage A system-level test case A stimulus/response pair Behavior that results from a sequence of system-level inputs An interleaved seq. of port input and output events ……. A seq. of ASFs PP3 Explain in your own words the interleaved seq of… events. System Testing

Examples of threads from the ATM Problem (Section 2.5 p27 of the text) Unit Testing Entry of a digit: (port entry of a numerical digit keystroke and a port out of a digit echo on the screen. This is a minimal “atomic system function” and qualifies as a thread of interest at the unit test level. Entry of a PIN number: (this entails a set of activities from screen request of a PIN with interleaved sequence of digit entry until completion - - - possibly including cancellation and up to three re-tries). This is a sequence of atomic system functions that also qualifies as a thread, probably fit for integration testing or unit testing levels. A simple ATM transaction: (this includes a set of functions such as 1) Card entry, 2) PIN entry, 3) choice of transaction type (deposit, withdraw, account detail processing, etc.) This is a sequence of atomic system functions that is a thread & accomplishes a major function, fit for integration testing or system testing levels . Multiple ATM transactions: (this includes a complete user session where several different transactions- - - query, withdraw, deposit of different accounts - - - may transpire.) This is a sequence of different/multiple threads and is definitely in the domain of system testing. System Testing System Testing

Some definitions related to thread An atomic system function (ASF) is an action that is observable at the system level in terms of port entry and port output. An ASF graph is a directed graph of a ASF represented system where the nodes are the ASF’s and the edges represent the sequential flow. A source ASF is an ASF that is a source node in an ASF graph. A sink ASF is an ASF that is a sink node in an ASF graph. A system thread is a path from a source ASF to a sink ASF in the ASF graph of the system. The thread graph of a system is a directed graph where the a) nodes are the threads of the system and b) the edges represent the sequential execution flow from one thread to another. 4/13 PP4 – Explain the source and sink nodes. System Testing

Requirements Specification for System Testing Requirements specification served as a tool (input) for, mainly black-box testing, but also white-box testing even at the unit testing level; it is even more important as a source of developing test cases for system testing. There are many ways to express requirements and many ways to view the specification. As a whole the requirements specification may be viewed a set of inter-related elements (“basis” for requirements): Data (information and information structure) Actions (functional tasks) Devices (for input, output, and storage) Events (triggers and combination of action and data) Threads (business flow or process flow, involving events) System Testing Only thing missing is the non-functional attribute such as quality, performance, etc.

Multiple Ways of Viewing Specification “Basis” elements Used mostly for early spec and development of system devices Data Contextual model Actions Behavior model Devices Often used for requirements specifications Events Structural model Threads Used mostly for development There are many tools for expressing these models: (e.g.) - state transition diagram ( or Finite State Machine) - E-R diagram - Petri net System Testing

Using Finite State Machine or State Transition Diagram Welcome Card entry (state A) State Input Next State Output A correct card B screen 2 A bad card A screen 1; card B good pin # C screen 5 B failed pin # A screen 4 wrong card Display screen 1; Eject card Correct card Display screen 2 Pin Entry (state B) Failed Pin Process Display screen 4 Successful Pin Process Tabular form Display screen 5 Choosing Transaction (state C) Graphical form System Testing

Finite State Machine at a “deeper” level for PIN processing Welcome Card entry (state A) Incorrect Pin/ cancel wrong card Display screen 4, 1 Display screen 1; Eject card Correct card Display screen 2 1st Pin Entry (state B) Incorrect Pin/ cancel 2nd Pin Entry (state D) Incorrect Pin/ cancel 3rd Pin Entry (state E) Display screen 3, 2 Successful Pin Process Display screen 3, 2 Correct Pin Display screen 5 Choosing Transaction (state C) Display screen 5 Correct Pin System Testing Display screen 5

4/18 Details of PIN Entry as a Thread A screen requesting PIN digits. An interleaved sequence of digit keystrokes and screen responses. The possibility of cancellation by the customer before the full PIN is entered. A system disposition: A customer has three chances to enter the correct PIN. Once a correct PIN has been entered, the user sees a screen requesting the transaction type. After three failed PIN Entry attempts, a screen advises the customer that the ATM card will not be returned, and no access to ATM functions is provided.

4/18 Definition: Atomic System Function Definition: An Atomic System Function (ASF) is an action that is observable at the system level in terms of port input and output events. About ASFs characterized by a sequence of port level inputs and outputs could be just a simple stimulus/response pair (e.g. digit entry) Sample ASFs in our ATM example card entry PIN entry Transaction selection session termination

4/18 More Definitions… Given a system defined in terms of atomic system functions, the ASF Graph of the system is the directed graph in which nodes are ASFs and edges represent sequential flow. A source ASF is an Atomic System Function that appears as a source node in the ASF graph of a system. A sink ASF is an Atomic System Function that appears as a sink node in the ASF graph. A system thread is a path from a source ASF to a sink ASF in the ASF graph of a system.

4/18 Basis Concepts for Requirements Specification All of requirements specification models are developed on these basis concepts. Data Inputs to actions Outputs of actions Events Actions Threads (sequences of actions) Devices

4/18 E/R Model of Basis Concepts

4/18 SATM System User Interface

4/18 SATM System Screens

4/18 Uppermost Level of the SATM Finite State Machine

4/18 Details of SATM PIN Entry State

4/18 Details of SATM PIN Try State

4/18 Paths in the SATM PIN Try State Correct PIN on first try state sequence <S2.n.0, S2.n.1, S2.n.2, S2.n.3, S2.n.4, S3> Port Event Sequence 1st digit, echo “- - - *” 2nd digit, echo “- - * *” 3rd digit, echo “- * * *” 4th digit, echo “* * * *” Enter Failed PIN on first try state Sequences <S2.n.0, S2.n.6> <S2.n.0, S2.n.1, S2.n.6> <S2.n.0, S2.n.1, S2.n.2, S2.n.6> <S2.n.0, S2.n.1, S2.n.2, S2.n.3, S2.n.6> <S2.n.0, S2.n.1, S2.n.2, S2.n.3, S2.n.4, S2.n.6>

4/18 How Many Paths in the PIN Try State? 1st try: 1 correct + 5 failed attempts 2nd try: 5 failed 1st attempts * 6 second attempts 3rd try: 25 failed 1st and 2nd attempts * six third attempts Do we really want to test all of these? This foreshadows the question of “long” versus “short” use cases.

4/18 Port Event Sequence: Correct PIN on 1st Try Port Input Event Port Output Event Screen 2 displayed with ‘- - - -’ 1st digit Screen 2 displayed with ‘- - - *’ 2nd digit Screen 2 displayed with ‘- - * *’ 3rd digit Screen 2 displayed with ‘- * * *’ 4th digit Screen 2 displayed with ‘* * * *’ (valid PIN) Screen 5 displayed 4/20 PP – This event sequence would have a Use case ID and description. Why?

4/18 Use Case: Correct PIN on 1st Try Use Case Name Correct PIN entry on first try Use Case ID EEUC-1 Description A customer enters the PIN number correctly on the first attempt. Pre-Conditions 1. The expected PIN is known 2. Screen 2 is displayed Event Sequence Input events Output events   1. Screen 2 shows '- - - - ' 2. Customer touches 1st digit 3. Screen 2 shows '- - - * ' 4. Customer touches 2nd digit 5. Screen 2 shows '- - * * ' 6. Customer touches 3rd digit 7. Screen 2 shows '- * * * ' 8. Customer touches 4th digit 9. Screen 2 shows '* * * * ' 10. Customer touches Enter 11. Screen 5 is displayed Post conditions  Select Transaction screen is active PP 4/20 – Do you see the information asked about in the last slide?

System Test Case: Correct PIN on 1st Try Test Case Name, ID Correct PIN entry on first try, TC-1 Description A customer enters the PIN number correctly on the first attempt. Pre-Conditions 1. The expected PIN is ‘2468’ 2. Screen 2 is displayed Event Sequence Input events Output events   1. Screen 2 shows '- - - - ' 2. Customer touches digit 2 3. Screen 2 shows '- - - * ' 4. Customer touches digit 4 5. Screen 2 shows '- - * * ' 6. Customer touches digit 6 7. Screen 2 shows '- * * * ' 8. Customer touches digit 8 9. Screen 2 shows '* * * * ' 10. Customer touches Enter 11. Screen 5 is displayed Post conditions  Select Transaction screen is active Test Result, Run by Pass, Paul Jorgensen

4/18 Event-Driven Petri Net of Correct PIN on First Try Physical connection require a harness that connects the PC with prototype ports. The test case language consists of the CAUSE and VERIFY verbs, names for port I/O events and device names.

4/18 Automated Test Case Execution Basic architecture: Use cases interpretively executed CAUSE inputs VERIFY outputs Check observed versus expected outputs via a harness connected to the System Under Test

4/18 Executable Test Case for Correct PIN on First Try Set up requirements: Screen 2 is displayed CAUSE TouchDigit(2) VERIFY Screen 2 shows ‘---*’ CAUSE TouchDigit(4) VERIFY Screen 2 shows ‘--**’ CAUSE TouchDigit(6) VERIFY Screen 2 shows ‘-***’ CAUSE TouchDigit(8) VERIFY Screen 2 shows ‘****’ VERIFY Screen 5 is displayed

4/18 Long versus Short Use Cases A “Long” use case is typically an end-to-end transaction. SATM example: A full traversal of the high level finite state machine, from the Welcome screen to the End Session screen: <s1, s2, s3, s4, s5> A “Short” use case is at the level on an atomic system function. Examples PIN Entry Transaction selection Session closing

4/18 Short Use Cases A “Short” use case is at the level on an atomic system function (ASF). In the directed graph of ASFs, nodes are ASFs edges signify possible sequential execution of ASFs Consider an ASF as a “Short” use case, with pre-conditions post-conditions Short use case (ASF) B can follow short use case (ASF) A if the pre-conditions of B are consistent with the post-conditions of A, that is... Short use cases “connect” at their pre- and post condition boundaries.

4/18 Short Use Cases for the SATM System Description SUC1 Valid ATM card swipe SUC2 Invalid ATM card swipe SUC3 Correct PIN attempt SUC4 Failed PIN attempt SUC5 Choose Balance SUC6 Choose Deposit SUC7 Choose Withdrawal: valid withdrawal amount SUC8 Choose Withdrawal: amount not a multiple of $20 SUC9 Choose Withdrawal: amount greater than account balance SUC10 Choose Withdrawal: amount greater than daily limit SUC11 Chose no other transaction SUC12 Chose another transaction

4/18 Short Use Cases for Failed PIN Attempts Description SUC13 Digit 1 entered SUC14 Digit 2 entered SUC15 Digit 3 entered SUC16 Digit 4 entered SUC17 Enter with valid PIN SUC18 Cancel before digit 1 SUC19 Cancel after digit 1 SUC20 Cancel after digit 2 SUC21 Cancel after digit 3 SUC22 Cancel after digit 4 SUC23 Enter with invalid PIN SUC24 Next PIN try SUC25 Last PIN try

4/18 How Many Use Cases? 1909 “long” use cases 25 “short” use cases Ways to determine “how many? Incidence with input events (cover every input event) Incidence with output events (cover every output event) Incidence with classes (need a use case/class incidence matrix) These lead directly to system testing coverage metrics.

4/18 Short Use Cases for the SATM System

4/18 System Testing with Short Use Cases Basic idea: a short use case is an atomic system function (ASF) ASFs ... begin with a port input event end is one of possibly several port output events ASFs can be identified in source code in executable models from short use cases Example: the integration version of NextDate (see text)

Using Operational Profile when interested in “Effectiveness” The effectiveness of testing is often measured in terms of problems found versus effort spent or (# of defects found) / person hours spent (# of defects found) / number of test cases Historically, most of the failures also tend to fall in small parts of the system (80% failures occur in 20% of the system - - - e.g. the most heavily traversed threads). Thus if we can collect the operational profiles of the users, we can identify the most heavily used threads. This strategy of system testing with operational profile can improve our test efficiency. Not just the number of problems found

Threads with Finite State Machine If we can model the requirements specifications with the finite state machine model, then: A set of transitions (with inputs and outputs) can be a source of threads for system test because it covers: Events ( state and input) Action (state transition and output) Data (inputs and outputs) Thread (series of state transitions) The drawbacks are: that not all specifications “easily” fit this model that the determination of what depth level should the finite state machine be for system test; very low a level is more appropriate for unit or integration test System Testing

Test Coverage Metrics with Finite State Machine Every node (state) is covered. This is a very minimal coverage, much like every statement is covered (recall this from structural path testing) In our 1st state transition chart - - - this is equivalent to covering states A, B, and C with correct card and successful PIN processing. Every node and edge (transition) is covered This is a more complete coverage if the finite state machine is carried to deep enough level. System Testing

Strategies for Thread Testing Finite State Machine modeled systems Event based (state-input based): Each input event occurs A “typical” or “common” sequence of input events occur Each input event occurs in every “relevant” data context For a given context, all “inappropriate” input events occur For a given context, all possible (both appropriate & inappropriate) inputs events occur Event based (state-output based): Each output event occurs Each output event occurs for every “cause” Port-based (both input and output): Cover all input and out ports System Testing

Strategies for thread Testing Data Represented Systems Some software system requirements are better represented with E-R diagram. For E-R modeling used for specifications, the threads may be identified via: Looking at the cardinality of every relationship One-one One-many Many-one Many - many Looking at the participation factor of every relationship Looking at functional dependencies among relationships e.g. loaning a book that’s not available More importantly --- we want to make sure that the DB “access” is tested, along with threads such as a) shutdown -restart b) backup-recovery c) multiple access threads System Testing

Using Operational Profile when interested in “Effectiveness” The effectiveness of testing is often measured in terms of problems found versus effort spent or (# of defects found) / person hours spent (# of defects found) / number of test cases Historically, most of the failures also tend to fall in small parts of the system (80% failures occur in 20% of the system - - - e.g. the most heavily traversed threads). Thus if we can collect the operational profiles of the users, we can identify the most heavily used threads. This strategy of system testing with operational profile can improve our test efficiency. Not just the number of problems found System Testing

User-Operational Profile Example (naïve user versus experienced user) (20/20) (20/20) prob = .25 √ term naïve users (20/80) default f1 f4 (5/5) prob = .063 (5/10) f4 term Start (80 users) (5/10) (5/5) prob = .063 (10/60) f1 f6 term experienced users (60/80) (40/40) (40/40) (40/60) prob = .50√√ term f7 f2 Choice of f1,f2,f3 (10/60) (3/10) (3/3) prob = .037 term f4 f3 (7/10) (7/7) prob = .087 f5 Note that 2 usage cases take up 75% of operational profile ! term System Testing

Software changes and Regression Test In the life span of a software, we can anticipate changes that result in multiple cycles of fixes and release. Thus it needs to be retested to ensure that what worked before still works (did not get regressed). A common strategy is to re-run the complete system test over as the regression test A more economical strategy for regression test is to develop (1) new threads for the new areas and (2) only include those old threads that are affected by the new release. (Yes, there may be an element of risk) Think about the “neighborhood” testing strategy-last lecture System Testing