Questions tagged [assertions]

Assertions enables you to test your assumptions about your program. For example, if you write a method that calculates the speed of a particle, you might assert that the calculated speed is less than the speed of light.

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Assert same and equals in unit test

I have a function to be tested fn doNothing(Student student) { //do some other operations here. but student is unmodified return student; } And my unit test is var student = new Student("...
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14 votes
14 answers
6k views

Should I raise an exception/error when an optional argument is used but is not necessary?

Take this constructed example: def fetch_person(person_id, country_code=None): if is_fully_qualified(person_id): return person_source_1.fetch_person(person_id) else: return ...
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4 votes
5 answers
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Assertion statements: Remove or retain in production code

I'm working in a large company and am doing my first Java project here. We have certain code style guidelines. In the Java guideline, it is said that "assertions are only intended for debugging ...
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31 votes
9 answers
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"Dead programs tell no lies" in the context of GUI programs

In The Pragmatic Programmer, the authors write: One of the benefits of detecting problems as soon as you can is that you can crash earlier, and crashing is often the best thing you can do. The ...
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7 votes
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Is it a good idea to start a function with a bunch of assert statements?

Sometimes when I look at other people's code I see functions that make a bunch of assumptions about the inputs but do not explicitly assert their assumptions. For example, look at the code below: def ...
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Why don't people usually use asserts throughout their application?

I usually do Javascript and I like putting console.assert liberally in my application. It throws an error if the first argument is falsey. E.g.: console.assert(price > 0, 'Price isn\'t above 0') ...
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2 votes
3 answers
171 views

Design pattern: method that checks consistency of object's internal state

I have got a project in C++. Each of my classes has a method void assert_good() const. The usage of that method is solely for debugging purposes: if the object is an inconsistent/impossible internal ...
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3 answers
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Testing new feature in existing test?

A new feature is being developed. I want to test this feature in different scenarios. We have existing tests that correspond to this scenario (but they test other features). Should I : insert new ...
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7 votes
4 answers
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Should I use assertions in a function that calls a function that have already them?

Let F(x) be a function that calls G(x), in which x must be greater than 0. If G already does assert(x > 0), should F do it as well?
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1 answer
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Writing assertion for unit testing queue data structure

I have data structure queue with 2 operations: typedef struct queue queue void enqueue(queue *q, void *elem); void *dequeue(queue *q); queue *read_from_file(const char *path); I want to write ...
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2 answers
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Dealing with assumptions in modules that result in duplicate work

Imagine a game that needs to score words. A words needs to be scored immediately, in a list of words or even in a list of words from list of players. I've created a scoring module which has the ...
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25 votes
8 answers
18k views

Should there be assertions in release builds

The default behavior of assert in C++ is to do nothing in release builds. I presume this is done for performance reasons and maybe to prevent users from seeing nasty error messages. However, I'd ...
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18 votes
1 answer
3k views

Unit tests: deferred assertions with Linq

Is it ok to add deferred assertions like this var actualKittens = actualKittens.Select(kitten => { Assert.IsСute(kitten); return kitten }); Why? So I can iterate just once even with ...
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4 votes
3 answers
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Why should we never `assert` that a library call doesn't fail with a certain error code?

From man 3 assert_perror: The purpose of the assert macros is to help programmers find bugs in their programs, things that cannot happen unless there was a coding mistake. However, with system or ...
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1 vote
3 answers
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When to use asserts vs unit tests or both?

Background: I'm creating my first C++ game project and I plan on calling a InitialThirdPartySystems() function to...well...intialize all third party systems to be used in my code lol. Within it I ...
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1 answer
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Generic Asserts in Unit Tests

I've been dealing with a Sr Dev recently that loves unit testing. That's great! I'm not sure I agree with his testing methods though, contrived example: function foo (String $var) { switch ($var) ...
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1 vote
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Pros and cons of asserting on the DB level in selenium tests

Consider a Selenium test that does some steps on the UI (e.g. fill a field and then click a save button), and afterwards checks with a DB query if the data entered in the new field was really saved ...
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1 answer
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Dealing with conditional verification logic using guard assertion

I have parametrized test with 2 variants: NULL value and any NOT NULL value From this value is depends one assert: In case NULL it should be checked if object has field1 with value1 In case ...
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6 votes
1 answer
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Strategies to increasing the maintainability of assertions in code [closed]

Background I am writing a compiler for a custom language for a school project and it is going really well for me. If I where to start all over from scratch I would have done many software ...
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4 votes
4 answers
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Purpose of assertion messages

Some languages and libraries can associate assertion messages with assertions. Such assertion messages are included in error messages when the assertion does not hold. Examples are Java, Class::...
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4 votes
2 answers
4k views

When is it ok to assert for a pointer being non-null?

This came up as part of a code review for a code segment which resembled this: auto somePikachu = GetMeAPikachu(); NT_ASSERT(somePikachu != nullptr); // this only fires on debug build somePikachu->...
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4 votes
1 answer
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sanity checks: when do they become paranoid checks [closed]

I normally add lots of sanity check clauses in my code. In other words, lots of assertions where the code is instructed to "panic" (usually print as much information as possible when a certain ...
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0 votes
3 answers
306 views

Is it good style to check explicitly for null in unit tests?

Whether or not a value is null could be checked implicitly like this: assertThat(value).isEqualTo("something"); Or it could be checked explicitly: assertThat(value).isNotNull(); assertThat(value)....
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3 votes
2 answers
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How to (or should I) have one assert per test with object comparisons? [duplicate]

I've recently read The Art of Unit Testing by Roy Osherove which I found very useful for helping me establish how to define a good unit test. One key aspect of the guidelines Roy puts forward are to ...
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3 votes
1 answer
1k views

Assert Message in Unit Tests

I've just begun reading "The Art Of Unit Testing" by Roy Osherove, and while I'm mostly finding the material very helpful, he makes a statement about not using messages in your Assert statements. ...
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6 votes
1 answer
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Advantages of using the library PyContracts over assert statements

Today I stumbled upon the python package called PyContracts. However, python has the assert statement which seems to allow you to do exactly those things. What advantages do contracts have over assert ...
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23 votes
3 answers
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Python - assert vs if & return

I am writing a script that does something to a text file (what it does is irrelevant for my question though). So before I do something to the file I want to check if the file exists. I can do this, no ...
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  • 355
0 votes
1 answer
162 views

Using a flag in in-memory-repository to indicate update to entity

I'm about to write a lot of test for my application. While some of the tests check whether everything works if the user enters the right data, most of them deal with wrong/missing data. In these cases ...
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11 votes
1 answer
5k views

Duck typing, data validation and assertive programming in Python

About duck typing: Duck typing is aided by habitually not testing for the type of arguments in method and function bodies, relying on documentation, clear code and testing to ensure correct use. ...
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1 vote
2 answers
3k views

Assertions vs Exceptions - is my understanding of the differences between the two correct? [duplicate]

Design By Contract uses preconditions and postconditions of the public methods in a class together to form a contract between the class and its clients. a) In code we implement preconditions and ...
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2 votes
2 answers
450 views

About the usage of assertions [duplicate]

I stumbled upon an article named Programming With Assertions. And beside the mechanism of turning on and off assertions after compile time, I don't get it. Why were assertions introduced on language ...
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5 votes
2 answers
506 views

Is it ok to use static (compile-time) assertions in unit tests?

Or more generally: to trigger compiler errors in test projects if something that can be checked at compile time is wrong?
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5 votes
3 answers
769 views

How much to test in TDD?

I am newbie to TDD (writing first project following TDD practices). I have fairly basic interface IProfiler and an implementation Profiler. interface IProfiler { bool IsBusy {get;} long Elapsed {...
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26 votes
3 answers
11k views

Should I still use Debug.Assert today?

I recently came across some newly written code that was interspersed with lots of Debug.Assert (C#). Should we still use this widely despite the usage of TDD, BDD and Unit Testing in general?
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21 votes
9 answers
3k views

Are too many assertions code smell?

I've really fallen in love with unit testing and TDD - I am test infected. However, unit testing is normally used for public methods. Sometimes though I do have to test some assumptions-assertions ...
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1 vote
3 answers
747 views

Is Debug.Assert obsolete if you write unit tests?

Just like the question asks, is there a need to add Debug.Assert into your code if you are writing unit tests (which has its own assertions)? I could see that this might make the code more obvious ...
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3 votes
3 answers
231 views

Should I create my own Assert class based on these reasons?

The main reason I don't like Debug.Assert is the fact that these assertions are disabled in Release. I know that there's a performance reason for that, but at least in my situation I believe the gains ...
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  • 625
9 votes
5 answers
799 views

Asserting in public methods [duplicate]

I'm a fan of using assertions in the code to check for preconditions. The question is whether is it wise to use assertions in public methods to check the precondition? My personal opinion is, that if ...
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10 votes
2 answers
628 views

code contracts/asserts: what with duplicate checks?

I'm a huge fan of writing asserts, contracts or whatever type of checks available in the language I'm using. One thing that bothers me a bit is that I'm not sure what the common practice is for ...
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13 votes
5 answers
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How can I improve my error checking and handling?

Lately I have been struggling to understand what the right amount of checking is and what the proper methods are. I have a few questions regarding this: What is the proper way to check for errors (...
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37 votes
9 answers
6k views

Is possible to write too many asserts?

I am a big fan of writing assert checks in C++ code as a way to catch cases during development that cannot possibly happen but do happen because of logic bugs in my program. This is a good practice in ...
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2 votes
5 answers
565 views

Assertions in private functions - Where to draw the line?

We use assertions to check for illegal behaviour which just shouldn't happen if everything is working as it should be, such as using NULL as argument when it clearly shouldn't. This is all very well ...
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58 votes
3 answers
14k views

Are asserts or unit tests more important?

Both asserts and unit tests serve as documentation for a codebase, and a means of discovering bugs. The main differences are that asserts function as sanity checks and see real inputs, whereas unit ...
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66 votes
5 answers
21k views

When to use assertions and when to use exceptions?

Often when I write a functions I want to make sure the inputs to it are valid in order to detect such errors as early as possible (I believe these are called preconditions). When a precondition fails, ...
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