Exercises Software Development I. 02 Algorithm Testing & Language Description Manual inspection, test plan, grammar, metasyntax notations (BNF, EBNF)

Transcription

1 Exercises Software Development I 02 Algorithm Testing & Language Description Manual inspection, test plan, grammar, metasyntax notations (BNF, EBNF) October 15th, 2014 Software Development I Winter term 2014/2015 Priv.-Doz. Dipl.-Ing. Dr. Andreas Riener Institute for Pervasive Computing Johannes Kepler University Linz riener@pervasive.jku.at

2 I Remember: Slides marked this way contain important concepts and should be carefully reviewed! Algorithm Testing: Manual Inspection In order to understand an algorithm (especially one written by another person), it is necessary to understand how it works. To get an idea of its structure, operation sequences, etc. (i.e., what it does ), manual inspection is a reasonable approach Code review Dry run ( Schreibtischtest ) Procedure Put yourself in the place of a computer and pass through the algorithm in a gradual manner (step by step) Examine all important variables and note down their values on specific, neuralgic code positions (e.g., before a branch, in the body of a loop, etc.) Software Development I // Exercises // 02 Testing and Language Description // 2

3 I Example: Manual Inspection of Algorithm Sum Sum() Input: 1, 9, 6, 8, 0 sum = 0 read( number) while number > 0 sum = sum + number read( number) write( sum) Position 0 Position 1 Position 2 Variables: sum, number Neuralgic code positions Result: Position sum number 0 0??? Software Development I // Exercises // 02 Testing and Language Description // 3

4 Manual Code Inspection: Advantages and Disadvantages Advantages Accurate Warranty to find and identify all errors ( bugs ) Disadvantages Time consuming Not feasable as it comes to complex algorithms (e.g., deep recursions, nested loops, etc.) advice: simulate only central parts of an algorithm manually/by hand Software Development I // Exercises // 02 Testing and Language Description // 4

5 Algorithm Testing: Automatic Inspection Source-level debuggers can be used for assisted or automatic inspection of algorithms Step by step execution Variable inspection Flow control Breakpoint toggling etc. Live Demo Debugging of Sum.java Debug view of Sum.java in the Eclipse framework Software Development I // Exercises // 02 Testing and Language Description // 5

6 Algorithm Testing: Test Plan for Sum Quite simple to generate: Input Expected Output Program Results any integers sum of the integers up to the first nonpositive value 24. Text as input, for example characters Non integer numbers Tell the user this is an invalid input and ask them to re-enter a valid integer: e.g., Value not valid, re-enter: Tell the user this is an invalid input and ask them to re-enter a valid integer: e.g., Value not valid, re-enter: Software Development I // Exercises // 02 Testing and Language Description // 6

7 Algorithm Testing: Test Plan for Sum Quite simple to generate: Input Expected Output Program Results any integers Text as input, for example characters Non integer numbers sum of the integers up to the first nonpositive value 24 Why? Should this not cause a These errors are covered by the Input class. If you crash, use program error, etc.? System.in.* to read-in variable 10 values, you have to 10 take. care of input errors by yourself. For that reason, you are requested to cover all possible input errors already now in your programs! Tell the user this is an invalid input and ask them to re-enter a valid integer: e.g., Value not valid, re-enter: Tell the user this is an invalid input and ask them to re-enter a valid integer: e.g., Value not valid, re-enter: Not a valid int, please try again: Not a valid int, please try again: Software Development I // Exercises // 02 Testing and Language Description // 7

8 I SWE1 UE02 PrimeFact.zip Algorithm Testing: Prime Factor Decomposition (PrimeFact.java) Algorithm We are looking for an algorithm that determines and displays the prime factors of a number entered by the user. For more details on the prime factor decomposition see Input: positive integer numbers Output: prime factors of the entered number, in ascending order Examples Input: 2 Output: 2 Input: 6 Output: 2 * 3 (2x3) Ask yourself What are special cases of this algorithm? Try to generate a complete table Based on this table, create the test plan for the algorithm Software Development I // Exercises // 02 Testing and Language Description // 8

9 I Algorithm Testing: Prime Factor Decomposition (PrimeFact.java) Group 1: Special cases, boundary values -1 invalid input (only positive integers); has no prime factors 0 has no prime factors 1 has no prime factors 2 smallest value with prime factors (only one) 3 number with one prime factor 4 smallest input with two prime factors (same) 6 smallest value with two different prime factors 8 smallest value with more than 2 prime factors 256 multiple, same prime factors 8085 multiple prime factors, different size 1031 greater number with only one prime factor (= prime number) Group 2: Illegal inputs -1 invalid (negativ) hallo not a number 123hallo not a number 1.12 not integer exceeds max. input number Software Development I // Exercises // 02 Testing and Language Description // 9

10 I Algorithm Testing: Test Plan for PrimeFact.java Aim (Group 1) Input Expected output Program output smallest number w/o prime factor 0 0 has no prime factors? first number >0 with no prime factors 1 1 has no prime factors? smallest value with one prime factor 2 2? second value with one prime factor 3 3? smallest value with two prime factors 4 2 * 2? smallest value with two different prime factors 6 2 * 3? smallest value with more than 2 prime factors 8 2 * 2 * 2? smallest value with more than two prime factors (> 2) 27 3 * 3 * 3? number with multiple (equal) prime factors * 2 * 2 * 2 * 2 * 2 * 2 * 2? number with mutiple different prime factors * 5 * 7 * 7 * 11? larger number with only one prime factor ? Software Development I // Exercises // 02 Testing and Language Description // 10

11 I Algorithm Testing: Test Plan for PrimeFact.java (2) Aim (Group 1, cont.) Input Expected output Program output common case 10 2 * 5? common case * 3 * 3 * 3 * 11 * 11? common case * 2 * 3 * 11 * 101? Aim (Group 2) Input Expected output Program output negative number (smallest) -1 invalid, no prime factors? invalid, text instead of integer hallo valid number required? invalid, valid number folllowed by text 123hallo valid number required? invalid, float value valid number required? no/empty input (finalized with \n) valid number required? largest integer number ? largest integer number valid number required? largest negative integer number invalid, no prime factors? Software Development I // Exercises // 02 Testing and Language Description // 11

12 I Algorithm Testing: Test Plan...highly relevant for assignments in most of the exercise sheets we call for the inclusion of a test plan. Before actually testing your program (i.e., implementation of an algorithm) you have to think about WHICH behavior, what special cases should be tested? HOW to reach these cases in the program (input values)? WHAT is the expected result (i.e., output values)? Testplan (tabular form) should contain Case, input, expected result, program output for some normal cases all (!) special cases and boundary values (over-/underflow, division by zero, infinity, etc.) illegal input configurations For additional information see (German language only) Software Development I // Exercises // 02 Testing and Language Description // 12

13 (Programming) Language Description: Metasyntax

14 Programming Languages: Representation / Description Notation of algorithms (see last week!) Textual form (prose) Graphical representation (Nassi-Shneiderman diagram) flow chart structure chart Programming language The programming language itself calls also for a representation/description Grammar = syntactical rules of a (programming) language Syntax = sentence structure, order of symbols, instructions Semantics = the meaning of a program, code fragment, expression Such a rule base enables the compiler to detect and announce programming errors/mistakes already at compile time Software Development I // Exercises // 02 Testing and Language Description // 14

15 I Language Descriptions: Types of Notations Metasyntax notations Backus-Naur-Form (BNF) Extended Backus-Naur-Form (EBNF) BNF vs. EBNF BNF is a formal, mathematical oriented notation form to describe the syntax of the programming language ALGOL60 BNF only defines terminal symbols, nonterminal symbols (production rules) and alternatives EBNF is an extension of BNF to better (easier) define complex syntax (take use of e.g. recursive definitions) - EBNF extends BNF by adding additional constructs (see next slide) - readability of EBNF as apposed to BNF is much improved as well - functional range of BNF is similar to EBNF (each EBNF description can also be represented with BNF) Syntax diagram Finite-state machine more details on Turing machines etc. in other lectures Software Development I // Exercises // 02 Testing and Language Description // 15

16 I Metasyntax Notation: Example Positive Integers in BNF A positive Integer number is represented by at least one, but in general an arbitrary number of digits; no leading sign; zero (0) number included, e.g Nonterminal symbols Alternative RECURSION PosIntBNF = number number PosIntBNF number = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" Terminal symbols Software Development I // Exercises // 02 Testing and Language Description // 16

17 I Metasyntax Notation: Extended Backus-Naur-Form (EBNF) Terminal symbols are literal, final characters that cannot be broken down into smaller units (also called tokens ) if, while, for, int, class, etc. special characters, such as ;,. - % = " + Nonterminal symbols. Using production rules, nonterminal symbols can be refined by different combinations of terminal symbols, further nonterminal symbols and by using meta-symbols, e.g. Paragraph = Sentence { Sentence } Sentence = Subject Predicate Object EBNF defines several meta symbols also called control symbols : =,., [], {},, () (as opposed to BNF, which only defines the alternative or ) = Production rule. End of production rule [] occurrence: one time or never {} occurrence: optional (0, 1,, ) alternative (left or right side) () precedence (group for priority) Software Development I // Exercises // 02 Testing and Language Description // 17 Valid meta symbols in EBNF.

18 I Metasyntax Notation: Example Positive Integers in EBNF A positive Integer number is represented by at least one, but in general an arbitrary number of digits; no leading sign; zero (0) number included, e.g altered representation of the recursion production rules are terminated by a period PosIntEBNF = number {number}. number = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9". Software Development I // Exercises // 02 Testing and Language Description // 18

19 Derivation Tree (BNF): Example Positive Integers PosIntBNF = number number PosIntBNF number = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" Wanted: Derivation tree for the number 3140 PosIntBNF number PosIntBNF 3 number PosIntBNF 3 1 number PosIntBNF number Software Development I // Exercises // 02 Testing and Language Description // 19

20 Metasyntax Notation: Examples for BNF, EBNF Representation Example 1: Decimal numbers A decimal number is positive or negative has a leading minus sign or is unsigned has any number of pre-decimal places (but at least 1) has an optional decimal symbol (".") followed by any number of decimal places (again at least one digit) Examples Software Development I // Exercises // 02 Testing and Language Description // 20

21 Metasyntax Notation: Examples for BNF, EBNF Representation BNF representation: Decimal number BNFDec = "-" Decnumber Decnumber Decnumber = Digitlist Digitlist "." Digitlist Digitlist = Digit Digit Digitlist Digit = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" Software Development I // Exercises // 02 Testing and Language Description // 21

22 Metasyntax Notation: Examples for BNF, EBNF Representation EBNF representation: Decimal number EBNFDec = ["-"] Digitlist ["." Digitlist]. Digitlist = Digit {Digit}. Digit = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9". Software Development I // Exercises // 02 Testing and Language Description // 22

23 Derivation Tree (BNF, EBNF): Example Decimal Numbers BNFDec = "-" Decnumber Decnumber Decnumber = Digitlist Digitlist "." Digitlist Digitlist = Digit Digit Digitlist Digit = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" EBNFDec = ["-"] Digitlist ["." Digitlist]. Digitlist = Digit {Digit}. Digit = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9". Try on your own: Derivation tree for the number PI (3.1415) in BNF or EBNF Software Development I // Exercises // 02 Testing and Language Description // 23

24 Derivation Tree (BNF, EBNF): Example Decimal Numbers BNF representation: Software Development I // Exercises // 02 Testing and Language Description // 24

25 Derivation Tree (BNF, EBNF): Example Decimal Numbers EBNF representation: Software Development I // Exercises // 02 Testing and Language Description // 25

26 Metasyntax Notation: Examples for BNF, EBNF Representation Example 2: Date formats (Prose) Two date formats: (a) short form, (b) extensive version Short form: Day (numeric) followed by the month (numeric), and finally the year (numeric, last two digits only); the three values are separated by a. or / symbol (mixed usage not allowed) Extensive version: Identifier of the day of the week (English language) followed by a comma; after that, the date is continued with a month identifier (English language) and the day of the month in numeric format; after another comma the year (numeric, last two digits only) concludes a date In both notations it is allowed to insert any number of spaces ( ) between the individual values and symbols Examples short: , 15/ 10/ 14 long: Wednesday, October 15, 14 Software Development I // Exercises // 02 Testing and Language Description // 26

27 Metasyntax Notation: Examples for BNF, EBNF Representation EBNF representation: Date formats Date = ShortDate LongDate. ShortDate = Space Number Space ( "." Space Number Space "." "/" Space Number Space "/" ) Space YearNumber. LongDate = Day Space "," Space Month Space Number Space "," Space YearNumber. Day = "Monday" "Tuesday" "Wednesday" "Thursday" "Friday" "Saturday" "Sunday". Month = "January" "February" "March" "April" "May" "June" "July" "August" "September" "October "November" "December". Number = Digit [ Digit ]. YearNumber = Digit Digit. Digit = "0" "1" "2" "3" "4" "5" "6" "7" "8" "9". Space = {" "}. Software Development I // Exercises // 02 Testing and Language Description // 27

28 Language Descriptions: Types of Notations Syntax diagram Terminal symbols circles or ovals Nonterminal symbols rectangles '/' 'Monday' LongDate Alternatives illustrated as branches, T-junctions Software Development I // Exercises // 02 Testing and Language Description // 28

29 Syntax Diagram: Date Formats Date ShortDate Space Number Digit Digit LongDate YearNumber Digit Digit ShortDate Space Number Space 9. Space Number Space. / Space Number Space / Digit 8... Space YearNumber 0 Software Development I // Exercises // 02 Testing and Language Description // 29

30 Syntax Diagram: Date Formats (continued) LongDate Space Day Space, Space Month Space Number Space, Space YearNumber Monday January Day Tuesday... Month February... Sunday December Software Development I // Exercises // 02 Testing and Language Description // 30

31 Exercises Software Development I 02 Algorithm Testing & Language Description Manual inspection, test plan, grammar, metasyntax notations (BNF, EBNF) October 15th, 2014 Software Development I Winter term 2014/2015 Priv.-Doz. Dipl.-Ing. Dr. Andreas Riener Institute for Pervasive Computing Johannes Kepler University Linz riener@pervasive.jku.at