C - What does the Assert method do Is it still useful

Question

I am debugging with breakpoints and I realize the assert call  I thought it was only for unit tests  What does it do more than breakpoint  Since I can breakpoint  why should I use Assert

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In a debug compilation  Assert takes in a Boolean condition as a parameter  and shows the error dialog if the condition is false   The program proceeds without any interruption if the condition is true    If you compile in Release  all Debug Assert s are automatically left out

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Assert also gives you another opportunity to chuckle at Microsoft s UI design skills   I mean  a dialog with three buttons Abort  Retry  Ignore  and an explanation of how to interpret them in the title bar

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Assert can help you give separate messaging behavior between testing and release  For example    Debug Assert x  gt  2    will only trigger a break if you are running a  debug  build  not a release build   There s a full example of this behavior here

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Assert allows you to assert a condition  post or pre  applies in your code  It s a way of documenting your intentions and having the debugger inform you with a dialog if your intention is not met   Unlike a breakpoint  the Assert goes with your code and can be used to add additional detail about your intention

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You should use it for times when you don t want to have to breakpoint every little line of code to check variables  but you do want to get some sort of feedback if certain situations are present  for example   Debug Assert someObject    null   someObject is null  this could totally be a bug

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Assertions feature heavily in Design by Contract  DbC  which as I understand was introducted endorsed by Meyer  Bertand  1997  Object-Oriented Software Contruction   An important feature is that they mustn t produce side-effects  for example you can handle an exception or take a different course of action with an if statement defensive programming    Assertions are used to check the pre post conditions of the contract  the client supplier relationship - the client must ensure that the pre-conditions of the supplier are met eg  sends   5 and the supplier must ensure the post-conditions are met eg  delivers 12 roses   Just simple explanation of client supplier - can accept less and deliver more  but about Assertions   C  also introduces Trace Assert    which can be used for release code   To answer the question yes they still useful  but can add complexity readability to code and time difficultly to maintain  Should we still use them  Yes  Will we all use them  Probably not  or not to the extent of how Meyer describes    Even the OU Java course that I learnt this technique on only showed simple examples and the rest of there code didn t enforce the DbC assertion rules on most of code  but was assumed to be used to assure program correctness

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The way I think of it is Debug Assert is a way to establish a contract about how a method is supposed to be called  focusing on specifics about the values of a paramter  instead of just the type    For example  if you are not supposed to send a null in the second parameter you add the Assert around that parameter to tell the consumer not to do that   It prevents someone from using your code in a boneheaded way   But it also allows that boneheaded way to go through to production and not give the nasty message to a customer  assuming you build a Release build

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First of all Assert   method is available for Trace and Debug classes  Debug Assert   is executing only in Debug mode  Trace Assert   is executing in Debug and Release mode    Here is an example           int i   1   3             Debug Assert method in Debug mode fails  since i    4         Debug Assert i    3           Debug WriteLine i    3   i is equal to 3                Trace Assert method in Release mode is not failing          Trace Assert i    4           Trace WriteLine i    4   i is equla to 4             Console WriteLine  Press a key to continue               Console ReadLine      Run this code in Debug mode and then in Release mode     You will notice that during Debug mode your code Debug Assert statement fails  you get a message box showing the current stack trace of the application  This is not happening in Release mode since Trace Assert   condition is true  i    4    WriteLine   method simply gives you an option of logging the information to Visual Studio output

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From Code Complete  8 Defensive Programming 8 2 Assertions An assertion is code that   s used during development   usually a routine or macro   that allows a program to check itself as it runs  When a assertion is true  that means everything is operating as expected  When it   s false  that means it has detected an unexpected error in the code  For example  if the system assumes that a customer-information file will never have more than 50 000 records  the program might contain an assertion that the number of records is less than or equal to 50 000  As long as the number of records is less than or equal to 50 000  the assertion will be silent  If it encounters more than 50 000 records  however  it will loudly    assert    that there is a error in the program  Assertions are especially useful in large  complicated programs and in high-reliability programs  They enable programmers to more quickly flush out mismatched interface assumptions  errors that creep in when the code is modified  and so on  An assertion usually takes two arguments  a boolean expression that describes the assumption that   s supposed to be true and a message to display if it isn   t        Normally  you don   t want users to see assertion messages in production code  assertions are primarily for use during development and maintenance  Assertions are normally compiled into the code at development time and compiled out of the code for production  During development  assertions flush out contradictory assumptions  unexpected conditions  bad values passed to routines  and so on  During production  they are compiled out of the code so that the assertions don   t degrade system performance

[c#] C# - What does the Assert() method do? Is it still useful?

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