1. CS 406 Software Testing Fall 98 Part II : Functional Testing Aditya P. Mathur Purdue University Last update: July 19, 1998

2. Functional testing2 Part II: Functional testing 4 Learning objectives- –What is functional testing? –How to perform functional testing? What are clues, test requirements, and test specifications? How to generate test inputs? –What are equivalence partitioning, boundary value testing, domain testing, state testing, and decision table testing?

3. Functional testing3 What is functional testing? 4 When test inputs are generated using program specifications, we say that we are doing functional testing. 4 Functional testing tests how well a program meets the functionality requirements.

4. Functional testing4 The methodology 4 The derivation of test inputs is based on program specifications. 4 Clues are obtained from the specifications. 4 Clues lead to test requirements. 4 Test requirements lead to test specifications. 4 Test specifications are then used to actually execute the program under test.

5. Functional testing5 Test methodology Specifications Clues Test requirements Test specifications Test driver Program Oracle Expected behavior Actual behavior Program output is correct Program has failed; make a note and proceed with testing or get into the debug mode. or Until specs. Exhausted.

6. Functional testing6 Specifications 4 Inputs and tasks: –Given inputs –Perform tasks

7. Functional testing7 Specifications-continued 4 Input properties –Input –must satisfy 4 Function f is a pre-condition on input

8. Functional testing8 Specifications-continued 4 Two types of pre-conditions are considered: –Validated: those that are required to be validated by the program under test and an error action is required to be performed if the condition is not true. –Assumed: those that are assumed to be true and not checked by the program under test.

9. Functional testing9 Specification: example 4 For the sort program: –Inputs are: N pointer to a sequence of length N pointer to an area in memory where the output sequence is to be placed.

10. Functional testing10 Specification: example..continued –Tasks to be performed: Sort the sequence in ascending order Return the sorted sequence in an area provided. Return 1 if sorting is successful, -1 otherwise.

11. Functional testing11 Preconditions for sort 4 Validated: –N>0 –On failure return -1; sorting considered unsuccessful. 4 Assumed: –The input sequence contains N integers. –The output area has space for at least N integers.

12. Functional testing12 Deriving pre-conditions 4 Pre-conditions result from properties of inputs. 4 Example: –alpha_sequence(name) alpha_sequence is the string obtained from name by removing all characters other then A- Z, and a-z. Thus, if name is “A12C” then alpha_name is “AC”.

13. Functional testing13 Deriving pre-conditions-continued 4 This leads to the following pre-condition: –Validated: the string alpha_sequence(name) is shorter than name. –On failure: print “invalid name”. 4 This property could also lead to the pre- condition: –Assumed: the string alpha_ sequence(name) is shorter than name.

14. Functional testing14 Post-conditions 4 A post-condition specifies a property of the output of a program. 4 The general format of a post-condition is: –if condition then effect-1 {else effect-2} 4 Example: –For the sort program a post-condition is: if N>0 then {the output sequence has the same elements as in the input sequence and in ascending order.}

15. Functional testing15 Post-condition-continued –This could be stated more formally as: if N>0 then { and each is a member of the input sequence and sort returns 1. } else {the output sequence is undefined and sort returns -1. }

16. Functional testing16 Post-condition-continued 4 Another example: –if (A=B) and (B=C) then return “equilateral”; 4 Can you complete the above post-condition for a program that is required to classify a triangle given the length of three sides? 4 Convention: We will not nest if-then-else statements while specifying a post- condition.

17. Functional testing17 Incompleteness of specifications 4 Specifications may be incomplete or ambiguous. 4 Example post-condition: if user places cursor on the name field then read a string –This post-condition does not specify any limit on the length of the input string hence is incomplete.

18. Functional testing18 Ambiguous specifications 4 It also does not make it clear as to –whether a string should be input only after the user has placed the cursor on the name field and clicked the mouse or simply placed the cursor on the name field. and hence is ambiguous.

19. Functional testing19 Clues: summary 4 Clues are: –Pre-conditions –Post-conditions –Variables, e.g. A is a length implying thereby that its value cannot be negative. –Operations, e.g. “search a list of names” or “find the average of total scores” –Definitions, e.g. “filename(name) is a name is no spaces.”

20. Functional testing20 Clues-continued 4 Ideally variables, operations and definitions should be a part of at least one pre- or post- condition. 4 However, this may not be the case as specifications are not always written formally. 4 Hence look out for variables, operations, and definitions within a specification!

21. Functional testing21 Test requirements 4 A test requirement is a description of how to test the program that is under test. 4 Here is a sample test requirement for a program that classifies a triangle given the length of three sides. –A, B, C are non-zero and positive. –One of A, B, C is negative; error condition. –One of A, B, C is zero; error condition.

22. Functional testing22 Test requirements-derivation 4 Test requirements are derived from clues. 4 For example, consider the following pre- conditions (clues): Assumed: A, B, and C are lengths Validated: A>0, B>0, C>0 4 These pre-conditions on A, B, and C lead to the test requirement given above.

23. Functional testing23 Test requirements-derivation 4 Note that we have clumped pre-condition for each input variable into one condition. This is being done only for inconvenience. 4 It is recommended that pre-conditions be separated for each variable.

24. Functional testing24 Test requirements-derivation 4 Note also that each validated pre-condition results in at least two requirements: one for the validated part and the other for the failure part. 4 In our example above we did not list all requirements. For example, we are content with testing “one of A, B, C is negative; error condition.”

25. Functional testing25 Test requirements-derivation 4 Post-conditions also lead to test requirements. 4 For example, the partial post-condition: if (A=B) and (B=C) then return “equilateral” leads to the following test requirement: A=B and B=C.

26. Functional testing26 Compound validated pre-conditions 4 Compound pre-conditions are ones that use the and or or connectors. 4 Examples: validated compound pre- conditions: –Pre-condition: A and B –Pre-condition: user places the mouse over the name field and clicks it.

27. Functional testing27 Compound validated pre-conditions 4 The first of the above pre-conditions leads to four requirements: A true, B true(This is the validated part) A false, B true(This and the rest are failures) A true, B false A false, B false 4 You may work out the requirements for compound pre-condition with the or connector.

28. Functional testing28 Compound validated pre-conditions 4 Compound validated pre-conditions could become quite complex. 4 Example: (A and (B or C)) 4 Brute force method will lead to 8 test requirements.

29. Functional testing29 Compound validated pre-conditions 4 In general this will lead to too many test requirements. 4 We can prune them by leaving out those requirements that are unlikely to reveal a program error. 4 For example, consider the validated pre- condition: A or B.

30. Functional testing30 Pruning test requirements 4 There are four possible test requirements: A true, B true A false, B true A true, B false A false, B false 4 Consider a correct C implementation: if (!(A || B)) exit_with_error(“Error: A is %d, B is %d”, A, B); else.. {/* the validated code comes here.*/}

31. Functional testing31 Possible errors 4 Programmer forgets to check for one of the two cases resulting in the code: if (!A) exit_with_error(“Error: A is %d, B is %d”, A, B); or if (!B) exit_with_error(“Error: A is %d, B is %d”, A, B);

32. Functional testing32 Possible errors-continued 4 Or use a wrong logical operator as in: if (!(A && B)) exit_with_error(“Error: A is %d, B is %d”, A, B); 4 Let us analyze how the four different tests will perform in each of the four implementations: one correct, and three incorrect ones.

33. Functional testing33 Truth table: or condition A B!(A || B)!(A&&B) !A!B TFFTFT FTFTTF FFTTTT TTFFFF InputsCorrect implementation Incorrect implementations Notice this one: will it help find any of the three possible errors?

34. Functional testing34 Truth table analysis Case 1: –A test input with A=true and B=false will cause the correct program to evaluate the condition to false. –The two incorrect implementations, !(A&&B) and (!B) will evaluate the condition to true.

35. Functional testing35 Truth table analysis-continued –Both incorrect implementations will print the error message. –The oracle will observe that the correct and the incorrect implementations behave differently. –It will therefore announce failure for each incorrect implementation thereby pointing to an error. End of Case 1.

36. Functional testing36 Truth table analysis-continued Case 2: –Test input A=false and B=true will reveal the error in the two incorrect implementations, !(A&&B) and (!A). Case 3: –Test input A=false and B=false might find a fault in the then branch of the if condition.

37. Functional testing37 Truth table analysis-continued Case 4: –Test input A=true and B=true might find a fault in the else branch of the if condition. 4 Thus, all four test inputs are likely to be useful.

38. Functional testing38 Truth table analysis-continued 4 However, if we were to check for the correct implementation of the condition A or B, then only the first two inputs are necessary. 4 In this example, reducing the number of test specifications from 4 to 2 does not lead to any significant savings. When will the savings be significant?

39. Functional testing39 Assumed pre-conditions 4 Each assumed pre-condition is likely to result in a test requirement. 4 Example: –Assumed: MODE is “on ground” or “flying” –This leads to two requirements: MODE is “on ground”, MODE is not “flying” MODE is not “on ground”, MODE is “flying”

40. Functional testing40 Assumed pre-conditions –These can be simplified to: MODE is “on ground” MODE is “flying”

41. Functional testing41 Test requirements checklist 4 Obtaining clues and deriving test requirements can become a tedious task. 4 To keep it from overwhelming us it is a good idea to make a checklist of clues. 4 This checklist is then transformed into a checklist of test requirements by going through each clue and deriving test requirements from it.

42. Functional testing42 Test specifications 4 A test requirements indicates “how” to test a program. But it does not provide exact values of inputs. 4 A test requirement is used to derive test specification, which is the exact specification of values of input and environment variables.

43. Functional testing43 Test specifications-continued 4 There may not be a one-to-one correspondence between test requirements and test specifications. 4 A test requirement checklist might contain 50 entries. These might result in only 22 test specifications. 4 The fewer the tests the better but only if these tests are of good quality!

44. Functional testing44 Test specifications-continued 4 We will discuss test quality when discussing test assessment. 4 A test specification looks like this: –Test 2: global variable all_files is initially false. next_record is set to 1. –Upon return expect: all_files to be true next_record is last_record+1

45. Functional testing45 Test specifications-continued 4 Notice the format of a test specification: –Each test is given a number which serves as its identifier. –There is a set of input values. –There is a set of expected values upon return from execution. Any side effects on files or networks must also be specified here. In essence, all observable effects must be specified in the “Expect” part of a test specification.

46. Functional testing46 Test specifications-continued –Any side effects on files or networks must also be specified. In essence, all observable effects must be specified in the “Expect” part of a test specification. –Similarly, values of all input variables, global or otherwise, must also be specified.

47. Functional testing47 Test requirements to specifications 4 The test requirements checklist guides the process of deriving test specifications. 4 Initially all entries in the checklist are unmarked or set to 0. 4 Each time a test is generated from a requirement it is marked or the count incremented by 1.

48. Functional testing48 Test requirements to specifications 4 Thus, at any point in time, one could assess the progress made towards the generation of test specifications. 4 One could also determine how many tests have been generated using any test requirement.

49. Functional testing49 Test requirements to specifications 4 Once a test requirement has been marked or its count is more than 0 we say that it has been satisfied. 4 Some rules of thumb to use while designing tests: –Try to satisfy multiple requirements using only one test. –Satisfy all test requirements.

50. Functional testing50 Test requirements to specifications –Avoid reuse of same values of a variable in different tests. Generating new tests by varying an existing one is likely to lead to tests that test the same part of the code as the previous one. In testing, variety helps! 4 Though we try to combine several test requirements to generate one test case, this is not advisable when considering error conditions.

51. Functional testing51 Test requirements to specifications 4 For example, consider the following: –speed_dial, an interval speed_dial<0,error speed_dial>120, error –zones, an interval zones <5, error zones>10, error

52. Functional testing52 Test requirements to specifications –One test specification obtained by combining the two requirements above is: speed_dial=-1 zone=3 4 Now, if the code to handle these error conditions is:

53. Functional testing53 Test requirements to specifications if (speed_dial 120) error_exit(“Incorrect speed_dial”); if (zone 10) error_exit(“Incorrect zone”); –For our test, the program will exit before it reaches the second if statement. Thus, it will miss detecting the error in coding the test for zone. error

54. Functional testing54 Test requirements to specifications 4 Also, do not assume an error test to satisfy any other test requirement. 4 Example: –Consider the function: myfunction(int X, int Y); –A test for the erroneous value of X might not test the code that uses Y.

55. Functional testing55 Test requirements to specifications 4 Test specifications must not mention internal variables. Remember, a test specification aids in setting input variables to suitable values before the test begins. Values of internal variables are computed during program execution. 4 However, there are exceptions to the above rule. Can you think of one?

56. Functional testing56 Equivalence partitioning 4 The input domain is usually too large for exhaustive testing. 4 It is therefore partitioned into a finite number of sub-domains for the selection of test inputs. 4 Each sub-domain is known as an equivalence class and serves as a source of at least one test input.

57. Functional testing57 Equivalence partitioning 1 2 3 4 Input domain partitioned into four sub-domains. Too many test inputs. Four test inputs, one selected from each sub-domain.

58. Functional testing58 How to partition? 4 Inputs to a program provide clues to partitioning. 4 Example 1: –Suppose that program P takes an input X, X being an integer. –For X =0 task T2.

59. Functional testing59 How to partition?-continued –The input domain is prohibitively large because X can assume a large number of values. –However, we expect P to behave the same way for all X<0. –Similarly, we expect P to perform the same way for all values of X>=0. –We therefore partition the input domain of P into two sub-domains.

60. Functional testing60 Two sub-domains X<0X>=0 One test case: X=-3 Another test case: X=-15 All test inputs in the X<0 sub-domain are considered equivalent. The assumption is that if one test input in this sub-domain reveals an error in the program, so will the others. This is true of the test inputs in the X>=0 sub-domain also. Equivalence class

61. Functional testing61 Non-overlapping partitions 4 In the previous example, the two equivalence classes are non-overlapping. In other words the two sub-domains are disjoint. 4 When the sub-domains are disjoint, it is sufficient to pick one test input from each equivalence class to test the program.

62. Functional testing62 Non-overlapping partitions 4 An equivalence class is considered covered when at least one test has been selected from it. 4 In partition testing our goal is to cover all equivalence classes.

63. Functional testing63 Overlapping partitions 4 Example 2: –Suppose that program P takes three integers X, Y and Z. It is known that: X<Y Z>Y

64. Functional testing64 Overlapping partitions X<Y X>=Y Z>Y Z<=Y X Y X=3, Y=4, Z=7 X<Y, Z<=Y X=2, Y=3, Z=1 X>=Y, Z<=Y X=15, Y=4, Z=1 X>=Y, Z>Y X=15, Y=4, Z=7

65. Functional testing65 Overlapping partition-test selection 4 In this example, we could select 4 test cases as: –X=4, Y=7, Z=1satisfies X<Y –X=4, Y=2, Z=1satisfies X>=Y –X=1, Y=7, Z=9satisfies Z>Y –X=1, Y=7, Z=2satisfies Z<=Y 4 Thus, we have one test case from each equivalence class.

66. Functional testing66 Overlapping partition-test selection 4 However, we may also select only 2 test inputs and satisfy all four equivalence classes: –X=4, Y=7, Z=1satisfies X<Y and Z<=Y –X=4, Y=2, Z=3satisfies X>=Y and Z>Y 4 Thus, we have reduced the number of test cases from 4 to 2 while covering each equivalence class.

67. Functional testing67 Partitioning using non-numeric data 4 In the previous two examples the inputs were integers. One can derive equivalence classes for other types of data also. 4 Example 3: –Suppose that program P takes one character X and one string Y as inputs. P performs task T1 for all lower case characters and T2 for upper case characters. Also, it performs task T3 for the null string and T4 for all other strings.

68. Functional testing68 Partitioning using non-numeric data X: LC X:UC Y: null Y: not null X: LC, Y: null X: LC, Y: not null X: UC, Y: not null X: UC, Y: null LC: Lower case character UC: Upper case character null: null string.

69. Functional testing69 Non-numeric data 4 Once again we have overlapping partitions. 4 We can select only 2 test inputs to cover all four equivalence classes. These are: –X: lower case, Y: null string –X: upper case, Y: not a null string

70. Functional testing70 Guidelines for equivalence partitioning 4 Input condition specifies a range: create one for the valid case and two for the invalid cases. –e.g. for a<=X<=b the classes are a<=X<=b (valid case) X b (the invalid cases)

71. Functional testing71 Guidelines-continued 4 Input condition specifies a value: create one for the valid value and two for incorrect values (below and above the valid value). This may not be possible for certain data types, e.g. for boolean. 4 Input condition specifies a member of a set: create one for the valid value and one for the invalid (not in the set) value.

72. Functional testing72 Sufficiency of partitions 4 In the previous examples we derived equivalence classes based on the conditions satisfied by input data. 4 Then we selected just enough tests to cover each partition. 4 Think of the advantages and disadvantages of this approach!

73. Functional testing73 Boundary value analysis (BVA) 4 Another way to generate test cases is to look for boundary values. 4 Suppose a program takes an integer X as input. 4 In the absence of any information, we assume that X=0 is a boundary. Inputs to the program might lie on the boundary or on either side of the boundary.

74. Functional testing74 BVA: continued 4 This gives us 3 test inputs: X=0, X=-20, and X=14. –Note that the values -20 and 14 are on either side of the boundary and are chosen arbitrarily. 4 Notice that using BVA we get 3 equivalence classes. One of these three classes contains only one value (X=0), the other two are large!

75. Functional testing75 BVA: continued 4 Now suppose that a program takes two integers X and Y and that x1<=X<=x2 and y1<=Y<=y2. x1 x2 y2 y1 1 2 3 4 5 6 7 8 9 10 11 12 13 14

76. Functional testing76 BVA-continued 4 In this case the four sides of the rectangle represent the boundary. 4 The heuristic for test selection in this case is: –Select one test at each corner (1, 2, 3, 4). –Select one test just outside of each of the four sides of the boundary (5, 6, 7, 8)

77. Functional testing77 BVA-continued –Select one test just inside of each of the four sides of the boundary (10, 11, 12, 13). –Select one test case inside of the bounded region (9). –Select one test case outside of the bounded region (14). 4 How many equivalence classes do we get?

78. Functional testing78 BVA -continued 4 In the previous examples we considered only numeric data. 4 BVA can be done on any type of data. 4 For example, suppose that a program takes a string S and an integer X as inputs. The constraints on inputs are: – length(S)<=100 and a<=X<=b 4 Can you derive the test cases using BVA?

79. Functional testing79 BVA applied to output variables 4 Just as we applied BVA to input data, we can apply it to output data. 4 Doing so gives us equivalence classes for the output domain. 4 We then try to find test inputs that will cover each output equivalence class.

80. Functional testing80 BVA-continued 4 Example: each student to construct one!

81. Functional testing81 Finite State Machines (FSMs) 4 A state machine is an abstract representation of actions taken by a program or anything else that functions! 4 It is specified as a quintuple: A: a finite input alphabet Q: a finite set of states q0: initial state which is a member of Q.

82. Functional testing82 FSMs-continued T: state transitions which is a mapping Q x A--> Q F: A finite set of final states, F is a subset of Q. –Example: Here is a finite state machine that recognizes integers ending with a carriage return character. A={0,1,2,3,4,5,6,7,8,9, CR} Q={q0,q1,q2} q0: initial state

83. Functional testing83 FSMs-continued T: {((q0,d),q1),(q1,d),q1), (q1,CR),q2)} F: {q2} 4 A state diagram is an easier to understand specification of a state machine. For the above machine, the state diagram appears on the next page.

84. Functional testing84 State diagram q0q1 d d CR q2 Final state indicated by concentric circles. States indicated by circles. State transitions indicated by labeled arrows from one state the another (which could be the same). Each label must be from the alphabet. It is also known as an event. d: denotes a digit

85. Functional testing85 State diagram-actions q0q1 q2 d/set i to d d /add 10*d to i CR/output i i is initialized to d when the machine moves from state q0 to q1. i is incremented by 10*d when the machine moves from q1 to q1. The current value of i is output when a CR is encountered. Can you describe what this machine computes?Can you construct a regular expression that describes all strings recognized by this state machine? x/y: x is an element of the alphabet and y is an action.

86. Functional testing86 State machine: languages 4 Each state machine recognizes a language. 4 The language recognized by a state machine is the set S of all strings such that: –when any string s in S is input to the state machine the machine goes through a sequence of transitions and ends up in the final state after having scanned all elements of s.

87. Functional testing87 State diagram-errors q0q1 q2 d/set I to d d /add 10*d to I CR/output I q4 has been added to the set of states. It represents an error state. Notice that reset is a new member added to the alphabet. CR/output error q4 reset

88. Functional testing88 State diagram-program 4 A state diagram can be transformed into a program using case analysis. Here is a C program fragment that embodies logic represented by the previous state diagram. 4 There is one function for each action. 4 digit is assumed to be provided by the lexical analyzer.

89. Functional testing89 Program for “integer” state machine case q0: i=digit;/* perform action. */ state=q1;/* set next state. */ break;/* event digit is done. */ case q1: i=i+10*digit;/* Add the next digit. */ state=q1; break; /*…complete the program. */ /* state is global, with values q0, q1, q2. i is also global.*/ switch (state) void event_digit() {

90. Functional testing90 Checking state diagrams 4 Unreachable state: One that cannot be reached from q0 using any sequence of transitions. 4 Dead state: One that cannot be left once it is reached.

91. Functional testing91 Test requirements 4 Every state must be reached at least once, Obtain 100% state coverage. 4 Every transition must be exercised at least once.Obtain 100% transition coverage. 4 The textbook talks about duplicate transitions. No transitions are duplicate if the state machine definition we have given is used.

92. Functional testing92 Example test requirements 4 For the “integer” state machine: –state machine transitions: event digit in state q0 event CR in state q0 event digit in state q1 event CR in state q1 event reset in state q4

93. Functional testing93 More testing of state machines? 4 Yes, it is possible! 4 When we learn about path coverage we will discuss how more test requirements can be derived from a state diagram.

94. Functional testing94 Test specifications 4 As before, test specifications are derived from test requirements. 4 In the absence of dead states, all states and transitions can be reached by one test. 4 It is advisable not to test the entire machine with one test case. 4 Develop test specifications for our “integer” state machine.

95. Functional testing95 Decision tables 4 Requirements of certain programs are specified by decision tables. 4 Such tables can be used for deriving test requirements and specifications. 4 A decision table is useful when specifying complex decision logic

96. Functional testing96 Decision tables 4 A decision table has two parts: –condition part –action part 4 The two together specify under what condition will an action be performed.

97. Functional testing97 Decision table-nomenclature C: denotes a condition A: denotes an action Y: denotes true N:denotes false X: denotes action to be taken. Blank in condition: denotes “don’t care” Blank in action: denotes “do not take the action”

98. Functional testing98 Bank example 4 Consider a bank software responsible for debiting from an account. The relevant conditions and actions are: C1: The account number is correct C2: The signature matches C3: There is enough money in the account A1: Give money A2: Give statement indicating insufficient funds A3: Call vigilance to check for fraud!

99. Functional testing99 Decision tables

100. Functional testing100 Example-continued 4 A1 is to be performed when C1, C2, and C3 are true. 4 A2 is to be performed when C1 is true and C2 and C3 are false or when C1 and C2 are true and C3 is false. 4 A3 is to be performed when C2 and C3 are false.

101. Functional testing101 Default rules 4 Are all possible combinations of conditions covered? 4 No! Which ones are not covered? 4 We need a default action for the uncovered combinations. A default action could be an error report or a reset.

102. Functional testing102 Example-test requirements 4 Each column is a rule and corresponds to at least one test requirement. 4 If there are n columns then there are at least n test requirements. 4 What is the maximum number of test requirements?

103. Functional testing103 Example-test specifications 4 For each test requirement find a set of input values of variables such that the selected rule is satisfied. 4 When this test is input to the program the output must correspond to the action specified in the decision table. 4 Should the testing depend on the order in which the conditions are evaluated?

104. Functional testing104 Summary 4 Specifications, pre-conditions, and post- conditions. 4 Clues, test requirements, and test specifications. 4 Clues from code. 4 Test requirements catalog. 4 Equivalence partitioning and boundary value analysis.

105. Functional testing105 Summary-continued 4 Finite state machine 4 State diagram 4 Events and actions 4 Unreachable and dead states 4 Test requirements and specifications for state machines 4 Decision tables, rules, actions