i am currenty studying BDD, but i have a different doubt, can you tell me if the following is right or not:
1) Feature = it means "the problem" isn't it?
2) Scenario = the way (the beahaviour) to resolve the feature
I find very difficult to find the "given when then" sentences.
In this problem for example:
As a student
I would like / i want to calculate the rectangle perimeters if i have 2 number
Or the circle area if i have one
So i don't make mistake with the computation
I wrote down the scenario, is that correct?
Given 1 number
Or 2 number
When i have 1 positive number
Or 2 positive number
Then calculate the area
Or the Perimeters
About the terminology:
1) feature is not a "problem". It would rather be a solution.
In software programming, a feature is a something that your program does to solve a problem.
A feature could be the ability to compute the area of a rectangle.
2) a scenario is a description of the usage of your feature. Like an example.
Like a test case, but usually in a more human-readable form.
3) a story (in Agile terminology, in which BDD stands) is a way to describe the a need/problem.
Your problem ("as a student...") is presented as a story.
This story will lead to a new feature in your soft.
This new feature will be tested by scenarios.
About your scenarios.
Yours are not correct.
There is no way to know that if you have 1 nb you should compute an area.
You should have several scenarios, like
Given I send the number 2
When I launch the computation
Then I get the result 12,56
Given I send the number 2 and 3
When I launch the computation
Then I get the result 10
Given I send the number -4
When I launch the computation
Then I get the result error
Given I send the number 1 3 7
When I launch the computation
Then I get the result error
Related
I'm interested in knowing the possibilities of this. I'm working on a project that validates the skills of a software engineer, currently we validate skills based on code reviews by credentialed developers.
I know the answer if far more completed that the question, I couldn't imagine how complex the program would have to be able to analyse complex code but I am starting with basic programming interview questions.
For example, the classic FizzBuzz question:
Write a program that prints the numbers from 1 to 20. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz”.
and below is the solution in python:
for num in range(1,21):
string = ""
if num % 3 == 0:
string = string + "Fizz"
if num % 5 == 0:
string = string + "Buzz"
if num % 5 != 0 and num % 3 != 0:
string = string + str(num)
print(string)
Question is, can we programatically analyse the validity of this solution?
I would like to know if anyone has attempted this, and if there are current implementations I can take a look at. Also if anyone has used z3, and if it is something I can use to solve this problem.
As Vilx- mentioned, correctness of programs (including whether or not they terminate) is in general known to be undecidable. However, tools such as Z3 show that relevant concrete cases can still be reasoned about, despite the general undecidability of the problem.
Static analysers typically look for "simple" problems (e.g. null dereferences, out-of-bounds accesses, numerical overflows), but are comparably fast and require little user guidance (think of guidance in the spirit of adding type annotations to your code).
A non-exhaustive (and biased) list of keywords to search for: "static analysers", "abstract interpretation"; "facebook infer", "airbus absint", "juliasoft".
Verifiers attempt to prove much richer properties, in particular functional correctness, e.g. "does this sort-implementation really sort my array (and not do anything else, e.g. deallocate some global memory or update an element reachable from the array)?" or "does that crypto-implementation really implement the crypto protocol it promises to implement?". This is a much harder task and tools from that line of research are typically rather slow, require expert users with a background in formal verification and significant user guidance.
A non-exhaustive (and biased) list of keywords to search for: "verification", "hoare logic", "separation logic"; "eth viper", "microsoft dafny", "kuleuven verifast", "microsoft f*".
Other formal methods exist, e.g. refinement (or correct-by-construction), but with even less tool support and, as far as I know, industry acceptance.
Let's put it this way: it's been mathematically proven that you CANNOT determine if a program will ever terminate. So if you want a mathematically perfect answer of if the target program is correct, you're doomed.
That said, you can still do unit tests and "linting" which will give you plenty of intetesting insights.
But for simple pieces of code like the FizzBuzz, I think that eyeballing by an experienced dev will probably bring the best results.
I am currently working on a project which has some requirements for VBA. The data is found in excel. What I need to ask/bounce ideas off of is for a way to write some code that will abide to the following conditions:
where Xmw and Ymw are in megawatt, and X and Y are generation plants
Xmw=<1000 -always true
and
Ymw=<1000 -always true
2000=Xmw+Ymw -Equation 1
and
10=X+Y -Equation 2
Essentially, since the maximum absolute value of generation to increase and decrease is 2000, and the maximum amount of plants that can be used is 10. I'm stuck at this point because I can't find the relation between the 2 equations. Additionally, the existing program identifies generation to use, but it doesn't follow it to the 2 provided equations.
Existing programming identifies which generation plants are in the "pools" of X and Y.
Any help would be greatly appreciated.
I am posting this in an answer because it would be too much to post in a comment (please comment and let me know if this hits the mark)
You could use a conditional that looks something like this:
power_generated=Ymw+Xmw
if power_generated<>2000 then
'do stuff here to add another power plant to generation
'
'
if X+Y>10 then
'deal with the fact that you have not enough power plants to deal with your draw
end if
end if
I was trying to solve Google Code Jam problems and there is one of them that I don't understand. Here is the question (World Finals 2013 - problem C): https://code.google.com/codejam/contest/2437491/dashboard#s=p2&a=2
And here follows the problem analysis: https://code.google.com/codejam/contest/2437491/dashboard#s=a&a=2
I don't understand why we can use binary search. In order to use binary search the elements have to be sorted. In order words: for a given element e, we can't have any element less than e at its right side. But that is not the case in this problem. Let me give you an example:
Suppose we do what the analysis tells us to do: we start with a left bound angle of 90° and a right bound angle of 0°. Our first search will be at angle of 45°. Suppose we find that, for this angle, X < N. In this case, the analysis tells us to make our left bound 45°. At this point, we can have discarded a viable solution (at, let's say, 75°) and at the same time there can be no more solutions between 0° and 45°, leading us to say that there's no solution (wrongly).
I don't think Google's solution is wrong =P. But I can't figure out why we can use a binary search in this case. Anyone knows?
I don't understand why we can use binary search. In order to use
binary search the elements have to be sorted. In order words: for a
given element e, we can't have any element less than e at its right
side. But that is not the case in this problem.
A binary search works in this case because:
the values vary by at most 1
we only need to find one solution, not all of them
the first and last value straddle the desired value (X .. N .. 2N-X)
I don't quite follow your counter-example, but here's an example of a binary search on a sequence with the above constraints. Looking for 3:
1 2 1 1 2 3 2 3 4 5 4 4 3 3 4 5 4 4
[ ]
[ ]
[ ]
[ ]
*
I have read the problem and in the meantime thought about the solution. When I read the solution I have seen that they have mostly done the same as I would have, however, I did not thought about some minor optimizations they were using, as I was still digesting the task.
Solution:
Step1: They choose a median so that each of the line splits the set into half, therefore there will be two provinces having x mines, while the other two provinces will have N - x mines, respectively, because the two lines each split the set into half and
2 * x + 2 * (2 * N - x) = 2 * x + 4 * N - 2 * x = 4 * N.
If x = N, then we were lucky and accidentally found a solution.
Step2: They are taking advantage of the "fact" that no three lines are collinear. I believe they are wrong, as the task did not tell us this is the case and they have taken advantage of this "fact", because they assumed that the task is solvable, however, in the task they were clearly asking us to tell them if the task is impossible with the current input. I believe this part is smelly. However, the task is not necessarily solvable, not to mention the fact that there might be a solution even for the case when three mines are collinear.
Thus, somewhere in between X had to be exactly equal to N!
Not true either, as they have stated in the task that
You should output IMPOSSIBLE instead if there is no good placement of
borders.
Step 3: They are still using the "fact" described as un-true in the previous step.
So let us close the book and think ourselves. Their solution is not bad, but they assume something which is not necessarily true. I believe them that all their inputs contained mines corresponding to their assumption, but this is not necessarily the case, as the task did not clearly state this and I can easily create a solvable input having three collinear mines.
Their idea for median choice is correct, so we must follow this procedure, the problem gets more complicated if we do not do this step. Now, we could search for a solution by modifying the angle until we find a solution or reach the border of the period (this was my idea initially). However, we know which provinces have too much mines and which provinces do not have enough mines. Also, we know that the period is pi/2 or, in other terms 90 degrees, because if we move alpha by pi/2 into either positive (counter-clockwise) or negative (clockwise) direction, then we have the same problem, but each child gets a different province, which is irrelevant from our point of view, they will still be rivals, I guess, but this does not concern us.
Now, we try and see what happens if we rotate the lines by pi/4. We will see that some mines might have changed borders. We have either not reached a solution yet, or have gone too far and poor provinces became rich and rich provinces became poor. In either case we know in which half the solution should be, so we rotate back/forward by pi/8. Then, with the same logic, by pi/16, until we have found a solution or there is no solution.
Back to the question, we cannot arrive into the situation described by you, because if there was a valid solution at 75 degrees, then we would see that we have not rotated the lines enough by rotating only 45 degrees, because then based on the number of mines which have changed borders we would be able to determine the right angle-interval. Remember, that we have two rich provinces and two poor provinces. Each rich provinces have two poor bordering provinces and vice-versa. So, the poor provinces should gain mines and the rich provinces should lose mines. If, when rotating by 45 degrees we see that the poor provinces did not get enough mines, then we will choose to rotate more until we see they have gained enough mines. If they have gained too many mines, then we change direction.
I have created a game, (4 in a row), in prolog. My heuristic function requires me to know how many Player's and Opponent's chips are in each possible 4-row combination on the board. The method I am using is as follows (in psuedocodish):
I have 1 list of all possible fours of the board (ComboList) =of the form==> [[A,B,C,D]|Rest].
I have 1 list of all the moves of the 1st player (List1) =of the form==> [[1],[7],[14]]
And 1 for opponent's moves (List2).
Step 1: obtain the first combo from ComboList, 2:
Check all of List1 to see how many are in this combo, 3:
Check all of List2 to see how many are in this combo,
Move onto the next combo from ComboList and start over...
This PROCESS takes waay too much runtime for what is required.
Please can someone suggest something better and more efficient! Much thanks in advance!
The following code uses member/3, which has also to become
known as nth1/3. See here:
http://storage.developerzen.com/fourrow.pro.txt
The predicate is nowadays found in library(lists) and has
possibly native support or a fast implementation:
http://www.swi-prolog.org/pldoc/man?predicate=nth1/3
But I guess asserting some facts and relying on argument
indexing might get you an even better result. See for
example here:
http://www.mxro.de/applications/four-in-a-row
Hope this helps.
Bye
I understand how equivalence testing works.
How is it the same or different from boundary value testing?
Equivalence Class Testing
EC Testing is when you have a number of test items (e.g. values) that you want to test but because of cost (time/money) you do not have time to test them all. Therefore you group the test item into class where all items in each class are suppose to behave exactly the same. The theory is that you only need to test one of each item to make sure the system works.
Example 1
Children under 2 ride the bus for free. Young people pay $10, Adults $15 and Senior Citizen pay $5.
Classes:
Price:0 -> Age:0-1
Price:10 -> Age:2-14
Price:15 -> Age:15-64
Price:5 -> Age:65-infinity
Example 2 (more than one parameter)
Cellphones K80, J64 and J54 run Java 5. K90 and J99 run Java 6. But there are two possible browsers FireFox and Opera, J models run FF and K models run O.
Classes:
Browser:FF, Java:5 -> Phones:J64,J54
Browser:FF, Java:6 -> Phones:J99
Browser:O, Java:5 -> Phones:K80
Browser:O, Java:6 -> Phones:K90
Dangers Of Equivalence Class Testing
There is a danger of using EC Testing that is rarely mentioned in the testing books but is very important to remember.
Just because two items/values are suppose to be in the same class and behave the same, does not mean they DO behave the same.
That means that just because you test one value in the class that ALL values in the class behave the same. Real world example of mine is with cell phones that all had a certain Java Platform. They were suppose to all work the same but they didn't in reality. So testing just one value in a class is good, but not good enough. EC Testing is a good tool, but it's not fool proof and be careful with it. If test cases are cheap and fast (like automation), test more, or why not test them all!
Boundary Value Testing
BV Testing is when you decide to test the values on the edge of each Class you have identified. The theory is that most defects is around the edges of a class.
Example
Classes:
Price:0 -> Age:0-1 ( Boundary values 0, 1)
Price:10 -> Age:2-14 ( Boundary values 2, 14)
Price:15 -> Age:15-64 ( Boundary values 15, 64)
Price:5 -> Age:65-infinity ( Boundary values 65)
Critique of Boundary Value Testing
1) I, and other test professionals I have taken courses from, are not convinced that most defects are hidden around the edges of each class. And I have never seen any studies that proves this to be the case.
2) The fact that you need to use BV Testing proves that EC Testing is flawed since you test more than one value of each class.
3) It's easy to use when using values like integers. But what is a boundary value of class of phones models or browsers versions?
Hidden Boundary Value Testing
The boundary values of a class is often based on the specification of how the system should work. This is all good and well but most systems contain boundaries that are not explained in any spec and you will need to look for yourself. E.g. 'How many characters can I put into the test field before the system fails and breaks.','How big can the data file become before it so slow to read it gets annoying'.
Real world examples
- Pasting one million characters into a text area in FireFox 3.5 on win 7 crashes it
- ReCaptcha has a limit of 16003 characters, does your system handle the 413 that it passes back to it if somebody puts 16004+ characters in field. Or does it break
Summary
EC Testing and BV Testing are great tools and you should use them but they are not perfect and don't expect to find all defects using them. Use your know-how about the system and your intelligence and intuition to try more items and looks for other ways it could fail. And look for the hidden boundaries!
Boundary value analysis simply means to select values near the boundaries of the classes. So you are still dividing the input domain according to the classes then instead of selecting values from the middle of the class use values from the boundaries.
For example, if the input condition is a range from 20 to 70 then you have three classes of input
less than 20
between 20 and 70
more than 70
then for boundary value analysis select input = 19, 20, 21, 69, 70, 71. This type of analysis picks up errors on the boundaries.
The Equivalence testing needs to be supplemented with the Boundary value testing.
For example for equivalent testing of a function that takes values between 1 and 12
(say months of a year) the partitions would be:
values less than 1 (0,-1,-2), invalid partition
values between 1-12, valid partition
values greater than 12,invalid partition
For equivalence testing it is enough to pick one value as test input from each of these partition classes. That would mean tests with value of -2,6, and 15 would be considered enough to test behavior of the function. But these values doesn't catch Off-by-one error which can occur quite often.
With the boundary value testing the test inputs would be : -1,0,1,11,12,13 (at the boundaries), which would catch off-by-one errors.
I see both these testing methods to be a complement of each other.
Boundary value analysis is part or subset of equivalence partitioning. In boundary values analysis, instead of some random value, only values in the boundary are selected.
Boundary value analysis overcome the drawback of the Equivalance class partitioning. If a fix length is g9iven for eg. Mobile number (10 digit.)
The lower boundary in this case is - digit - 1 (ie. 10 - 1 =9)
The upper boundary in this case is - digit +1 (ie 10 + 1 =11)
Now we can perform test for the 9 and 11
Dynamic Testing Types –
Specification Based testing
A. Equivalance Partitioning
A1. Boundary value analysis
A2. Decision Tables
A3. Use case Testing
A4. State Transition testing
Structural Based testing
A. Test Coverage
B. Code coverage
C. Statement coverage
D. Decision coverage
Experience Based Testing
A. Error testing
B. Exploratory Testing
Equivalance Partitioning – It is a technique where tester divide the test conditions into groups and sets. System should handle them equivalently hence called equivalence classes. To test one condition from each partition will work to assume all condition will work in that partition.
EX >> Check addition of the single digit values. i.e. values between 0 and 9.
Values less than -9, i.e. -10,-11, …. (Invalid partition)
Values less than 0, i.e. -1,-2, …. till -9 (Valid Partition)
Values between 0-9 i.e. 0,1 …. till 9 (Valid Partition)
Values greater than 9, i.e. 10,11 (Invalid partition)
Testing the addition for any two values of each partition is enough.
Boundary value testing – It is based on testing at the boundaries between partition.
EX >> Consider below combination.
Addition of -9 and -10,
Addition of -10 and -11
Addition of 0 and -1
Addition of 0 and 1
Addition of 9 and 10
Addition of 11 and 10