Software testing - EXAMPLE

SOFTWARE TESTING Prepared by Ms. S. Shanmuga Priya Sr. AP/CSE, New Horizon College of Engineering Bangalore Karnataka India

CONCEPTS DISCUSSED • Fundamentals of testing: Basic Definitions, Test Cases, Identifying Test Cases, Fault Taxonomies, Levels of Testing, Generalized Pseudocode, The Triangle Problem, The NextDate Function, The Commission Problem, The SATM System, The Currency Converter, Saturn Windshield Wiper Controller, Garage Door Opener

SAMPLE TEST CASE FOR A CALCULATOR

SAMPLE QUESTION(s) • Explain about the various terminologies involved in understanding the basic testing concepts. • List out the various testing terminologies and explain it. • Describe the life cycle of software testing with suitable diagram.

INSIGHT FROM A VENN DIAGRAM • Software view – Code-based view  Considers what it is – Behavioral view  Considers what it does • Testing is fundamentally concerned with behavior • Difficulty for tester – the base documents are usually written by and for developers – the emphasis is therefore on code-based, instead of behavioral, information

• Consider a universe of program behaviors • Given a program and its specification, consider – set S  specified behaviors and – set P  programmed behaviors • PROBLEMS FACED BY TESTER What if certain specified behaviors have not been programmed? – Faults of omission What if certain programmed (implemented) behaviors have not been specified? –Faults of commission

CORRECT PORTION “Correct” portion  Behaviors that are both specified and implemented How to identify the test cases?

IDENTIFYING TEST CASES • Two fundamental approaches aka traditional testing methods are used to identify test cases 1. Functional Testing aka Specification-based Testing aka Black Box Testing 2. Structural Testing aka Code-based Testing aka White Box Testing

• Specification-based Testing –program can be considered to be a function that maps values from its input domain to values in its output range • How test cases are identified? –With the information used is the specification of the software

• Advantage of this approach / method: – Independent of how the software is implemented, so if the implementation changes, the test cases are still useful; and – test case development can occur in parallel with the implementation thereby reducing the overall project development interval • Disadvantages – significant redundancies may exist among test cases – Possibility of gaps of untested software

• Code-based Testing – Lends itself to the definition and use of test coverage metrics – Test coverage metrics provide a way to explicitly state the extent to which a software item has been tested

SAMPLE QUESTION(S) Classify the errors and faults based on the anomalies. Explain IEEE fault and error taxonomy.

• Process  refers to how we do something • Product  end result of a process • The point at which testing and Software Quality Assurance (SQA) meet is that SQA typically tries to improve the product by improving the process. • In that sense, testing is clearly more product oriented.

• Faults can be classified in several ways: –the development phase in which the corresponding • error occurred, • the consequences of corresponding failures, • difficulty to resolve, • risk of no resolution, and so on. • Software Anomalies  “a departure from the expected” (IEEE)

• Explain the various levels of testing with a neat diagram. SAMPLE QUESTION(S)

• Draw the dataflow diagram for a structured triangle program implementation. • With a neat diagram, explain the currency converter system. • With a neat diagram, explain the SATM system. SAMPLE QUESTION(S)

• The Triangle problem • The NextDate function • The Commission problem • The Automated Teller Machine • The Currency Converter • The Windshield-Wiper Controller • Garage Door Opener

TRIANGLE PROBLEM – PROBLEM STATEMENT • Simple Version: The triangle program accepts three integers, a, b, and c, as input. These are taken to be sides of a triangle. The output of the program is the type of triangle determined by the three sides: Equilateral, Isosceles, Scalene, or Not A Triangle

• Improved Version: “Simple version” plus better definition of inputs: The integers a, b and c must satisfy the following conditions: c1: 1<=a<=200 c4: a<=b+c c2: 1<=b<=200 c5: b<=a+c c3: 1<=c<=200 c6: c<=a+b

Program triangle1 ‘Fortran-like version Dim a, b, c, match As INTEGER

FLOWCHART FOR TRIANGLE PROBLEM

TRIANGLE PROBLEM CONT… Final Version: “Improved version” plus better definition of outputs: If an input value fails any of conditions c1, c2, or c3, the program notes this with an output message. For example: – “Value of a is not in the range of permitted values.” – “Value of b is not in the range of permitted values.” – “Value of c is not in the range of permitted values.” If values of a, b, and c satisfy conditions c1, c2, and c3, one of four mutually exclusive outputs is given: 1. If all three sides are equal, the program output is Equilateral. 2. If exactly one pair of sides is equal, the program output is Isosceles. 3. If no pair of sides is equal, the program output is Scalene. 4. If any of conditions c4, c5, and c6 is not met, the program output is NotATriangle.

PROBLEM STATEMENT NextDate is a function of three variables: month, date, and year. It returns the date of the day after the input date. The month, date, and year variables have integer values subject to these conditions: c1: 1<= month <=12 c2: 1<=day<=31 c3: 1812<=year<=2012

NEXTDATE FUNCTION – PROBLEM STATEMENT CONT… • If any of conditions c1, c2, or c3 fails, NextDate produces an output indicating the corresponding variable has an out-of-range value. • For example: – “Value of month not in the range 1..12”. – Because numerous invalid day–month–year combinations exist, NextDate collapses these into one message: “Invalid Input Date.”

An example for relationship among the variables

LEAP YEAR • Any year that is evenly divisible by 4 is a leap year. For example: 1988, 1992, and 1996 However, there is still a small error that must be accounted for. To eliminate this error, the Gregorian calendar stipulates that a year that is evenly divisible by 100 (for example, 1900) is a leap year only if it is also evenly divisible by 400. For this reason, the following years are not leap years: 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600 • This is because they are evenly divisible by 100 but not by 400 The following years are leap years:1600, 2000, 2400 • This is because they are evenly divisible by both 100 and 400

12 MONTHS OF THE YEAR • The Gregorian calendar and the Julian calendar both consist of the following twelve months: 1. January - 31 days 2. February - 28 days; 29 days in Leap Years 3. March - 31 days 4. April - 30 days 5. May - 31 days 6. June - 30 days 7. July - 31 days 8. August - 31 days 9. September - 30 days 10. October - 31 days 11. November - 30 days 12. December - 31 days How many have 28, 30 or 31 days? The Gregorian calendar has: 4 months with a length of 30 days 7 months that are 31 days long February is the only month that is 28 days long in common years and 29 days long in leap years

Case 4: month is 2: 'February If day < 28 Then tomorrowDay = day +1 Else If day = 28 Then If ((year is a leap year) Then tomorrowDay = 29 'leap year Else ‘not a leap year tomorrowDay = 1 tomorrowMonth = 3 Endif Else if day = 29 Then tomorrowDay = 1 tomorrowMonth = 3 Else Output (“Cannot have Feb”, day) EndIf EndIf EndCase Output (“Tomorrow’s date is “, tomorrowMonth, tomorrowDay, TomorrowYear) End NextDate

THE COMMISSION PROBLEM PROBLEM STATEMENT A rifle salesperson in the former Arizona Territory sold rifle locks, stocks, and barrels made by a gunsmith in Missouri. Locks cost $45, stocks cost $30, and barrels cost $25. The salesperson had to sell at least one complete rifle per month, and production limits were such that most of the salesperson could sell in a month was 70 locks, 80 stocks, and 90 barrels.

THE COMMISSION PROBLEM STATEMENT CONT… After each town visit, the salesperson sent a telegram to the Missouri gunsmith with the number of locks, stocks, and barrels sold in that town. At the end of a month, the salesperson sent a very short telegram showing –1 locks sold. The gunsmith then knew the sales for the month were complete and computed the salesperson’s commission as follows: 10% on sales up to (and including) $1000, 15% on the next $800, and 20% on any sales in excess of $1800 The commission program produced a monthly sales report that gave the total number of locks, stocks, and barrels sold, the salesperson’s total dollar sales, and, finally, the commission.

10% on sales up to (and including) $1000, 15% on the next $800, and 20% on any sales in excess of $1800 Locks cost $45, stocks cost $30, and barrels cost $25.

End Commission 10% on sales up to (and including) $1000, 15% on the next $800, and 20% on any sales in excess of $1800

THE SIMPLE AUTOMATIC TELLER MACHINE (SATM) THE SATM TERMINAL

SATM PROBLEM STATEMENT CONT… • Using a terminal with features, SATM customers can select any of the transaction types: deposits, withdrawals, and balance inquiries • These transactions can be done on two types of accounts: checking and savings • The SATM system communicates with bank customers via 15 screens (shown in figure)

SCREEN 1 – WELCOME SCREEN • When the bank customer arrives at an SATM station, SCREEN 1 is displayed

SCREEN 2 and SCREEN 4 • Bank customer accesses the SATM system with a plastic card encoded with a Personal Account Number (PAN) which is a key to an internal customer account file, containing, among other things, the customer account name and account information • If the customers’ PAN matches the information in the customer account file, the system presents screen 2 to the customer. • If the customer’s PAN is not found, screen 4 is displayed, and the card is kept.

SCREEN 3 and SCREEN 5 • At Screen 2, the customer is prompted to enter his or her Personal Identification Number (PIN) • If the PIN is correct, the system displays Screen 5; otherwise Screen 3 is displayed

SCREEN 4 • The customer has 3 chances to get the PIN correct; after three failures, Screen 4 is displayed, and the card is kept

SCREEN 6 • On entry to screen 5, the system adds two pieces of information to the customer’s account file, the current date and an increment to the number of ATM sessions • The customer selects the desired transaction from the option shown on screen 5; then the system immediately displays screen 6, where the customer chooses the account to which the selected transaction will be applied

• If balance is requested, the system checks the local ATM file for any unposted transactions and reconciles these with the beginning balance for that day from the customer account file. • Screen 14 is then displayed

PROBLEM STATEMENT • The application converts US dollars to any of four currencies: – Brazilian Reals, – Canadian Dollars, – European Union Euros – Japanese Yen • Currency selection is governed by the radio buttons which are mutually exclusive • When a country is selected, the system responds by completing the label; for examples, “Equivalent in…” becomes “Equivalent in Canadian dollars” if the Canada button is clicked • Also, a small Canadian flag appears next to the output position for the equivalent currency amount

PROBLEM STATEMENT CONT… • Either before or after currency selection, the user inputs an amount in US dollars • Once both tasks are accomplished, the user can click on the Compute button, the Clear button or Quit button • Clicking on Compute button results in the conversion of the US dollar amount to the equivalent amount in the selected currency • Clicking on the Clear button resets the currency selection, the US dollar amount and the equivalent currency amount and the associated label • Clicking on the Quit button ends the application

THE WINDSHIELD WIPER CONTROLLER

• Windshield wiper is controlled by a lever with a dial • The lever has four positions – OFF, INT (for intermittent), LOW, and HIGH • The dial has three positions, numbered simply 1, 2, and 3 • The dial position indicate three intermittent speeds, and dial position is relevant only when the lever is at the INT position The decision table wiper speeds (in wipes per minute) for the lever and dial positions

PROBLEM STATEMENT CONT… • The decision table below shows the windshield wiper speeds (in wipes per minute) for the lever and dial positions

Components : A drive motor, A drive chain, The garage door wheel tracks, A lamp, and An electronic controller

A system to open a garage door is composed of several components: a drive motor, a drive chain, the garage door wheel tracks, a lamp, and an electronic controller. This much of the system is powered by commercial 110 V electricity. Several devices communicate with the garage door controller—a wireless keypad (usually in an automobile), a digit keypad on the outside of the garage door, and a wall-mounted button. In addition, there are two safety features, a laser beam near the floor and an obstacle sensor. These latter two devices operate only when the garage door is closing. If the light beam is interrupted (possibly by a pet), the door immediately stops, and then reverses direction until the door is fully open. If the door encounters an obstacle while it is closing (say a child’s tricycle left in the path of the door), the door stops and reverses direction until it is fully open. There is a third way to stop a door in motion, either when it is closing or opening. A signal from any of the three devices (wireless keypad, digit keypad, or wall-mounted control button). The response to any of these signals is different—the door stops in place. A subsequent signal from any of the devices starts the door in the same direction as when it was stopped. Finally, there are sensors that detect when the door has moved to one of the extreme positions, either fully open or fully closed. When the door is in motion, the lamp is lit, and remains lit for approximately 30 seconds after the door reaches one of the extreme positions.

REFERENCE • Paul C. Jorgensen: Software Testing, A Craftsman’s Approach, 4th Edition, Auerbach Publications, 2013.

Software testing - EXAMPLE

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