Photo by on Filipe Resmini Unsplash Infinite code, smells! It smells because there are likely many instances where it could be edited or improved. Most of these smells are just hints of something that might be wrong. They are not required fixed per se… ( You should look into it though.) Previous Code Smells Part I Part II Part III Part IV Part V Part VI Part VII Part VIII Part IX Part X Part XI Part XII Part XIII Part XIV Part XV Let's continue... Code Smell 76 - Generic Assertions Don't make weak tests to create a false sensation of coverage. TL;DR: Test Assertions should be precise. Not too Vague and not too specific. There is no silver bullet. Problems False Negatives Lack of Trust Solutions Check the right case. Assert for a functional case. Don't test implementation. Sample Code Wrong square = Square(5)

assert square.area() != 0

# This will lead to false negatives since it is too vague Right square = Square(5)

assert square.area() = 25

# Assertion should be precise Detection With techniques we can find these errors on our tests. Mutation Testing Tags Testing Conclusion We should use development techniques like that request concrete business cases and make concrete assertions based on our domain. TDD Relations Code Smell 30 - Mocking Business Code Smell 52 - Fragile Tests More info Test Driven Development The Only Design Principle Mutation Testing Credits This smell was inspired by @ and used with his . Mario Cervera permission Photo by on Fleur Unsplash A program that produces incorrect results twice as fast is infinitely slower. John Osterhout Code Smell 77 - Timestamps Timestamps are widely used. They have a central issuing authority and do not go back, do they? TL;DR: Don't use timestamps for sequence. Centralize and lock your issuer. Problems Bijection Fault. Timestamp Collisions. Timestamp precision. Packet Disorders. Bad (Timestamp) for an Essential Problem (Sequencing). Accidental Implementation Solutions Use a centralizing sequential stamper. (NO, not a ). Singleton If you need to model a sequence, . model a sequence Sample Code Wrong # using time module
import time
  
# ts stores the time in seconds
ts1 = time.time()
ts2 = time.time() #might be the same!! Right numbers = range(1, 100000)
#create a sequence of numbers and use them with a hotspot

#or
sequence = nextNumber() Detection Timestamps are very popular on many languages and are ubiquitous. We need to use them just to model... timestamps. Tags Bijection Conclusion This smell was inspired by recent . Ingenuity software fault If we don't follow our rules and model sequences with time, we will face trouble. MAPPER Luckily, Ingenuity is a sophisticated Autonomous vehicle and has a robust fail-safe landing software. This video describes the glitch. https://www.youtube.com/watch?v=6IoMiwxL2wU Relations Code Smell 39 - new Date() Code Smell 32 - Singletons Code Smell 71 - Magic Floats Disguised as Decimals More info Timestamp proposed changes Build a Mapper What is wrong with software The most beautiful code, the most beautiful functions, and the most beautiful programs are sometimes not there at all. Jon Bentley Code Smell 78 - Callback Hell Processing an algorithm as a sequence of nested callbacks is not clever. TL;DR: Don't process calls in a callback way. Write a sequence. Problems Readability Hard to debug. Complexity Solutions Change callbacks to sequence calls. Extract repeated Code Refactor. Sample Code Wrong var fs = require('fs');

var fileWithData = '/hello.world';  
fs.readFile(fileWithData, 'utf8', function(err, txt) {  
    if (err) return console.log(err);

    txt = txt + '\n' + 'Add Data!';
    fs.writeFile(fileWithData, txt, function(err) {
        if(err) return console.log(err);
        console.log('Information added');
    });
}); Right var fs = require('fs');

function logTextWasAdded(err) {  
    if(err) return console.log(err);
    console.log('Information added');
};

function addData(error, actualText) {  
    if (error) return console.log(error);

    actualText = actualText + '\n' + 'Add data';
    fs.writeFile(fileWithData, actualText, logTextWasAdded);
}

var fileWithData = 'hello.world';  
fs.readFile(fileWithData, 'utf8', addData); Detection This problem shines at the naked eye. Many linters can detect this complexity and warn us. Tags Readability Complexity Conclusion Callback Hell is a very common problem in programming languages with futures or promises. Callbacks are added in an incremental way. There's no much mess at the beginning. Complexity without refactoring makes them hard to read and debug. Relations Code Smell 06 - Too Clever Programmer Code Smell 102 - Arrow Code There are two ways to write code: write code so simple there are obviously no bugs in it, or write code so complex that there are no obvious bugs in it. Tony Hoare Code Smell 79 - TheResult If a name is already used, we can always prefix it with 'the'. TL;DR: don't prefix your variables. Problems Readability Meaningless names Solutions Use intention revealing names. Avoid . Indistinct noise words Sample Code Wrong var result;

result = getSomeResult();

var theResult;

theResult = getSomeResult(); Right var averageSalary;

averageSalary = calculateAverageSalary();

//..

var averageSalaryWithRaises;

averageSalaryWithRaises = calculateAverageSalary(); Detection As with many of our naming conventions, we can instruct our linters to forbid names like . theXxx... Tags Readability Conclusion Always use intention revealing names. If your names collide use local names, extract your methods and avoid 'the' prefixes. Relations Code Smell 38 - Abstract Names More info . What is in a name . How To Be Great At Giving Meaningful Names Credits Photo by on Josue Michel Unsplash One difference between a smart programmer and a professional programmer is that the professional understands that clarity is king. Professionals use their powers for good and write code that others can understand. Robert C. Martin Code Smell 80 - Nested Try/Catch Exceptions are a great way of separating happy path versus trouble path. But we tend to over-complicate our solutions. TL;DR: Don't nest Exceptions. Nobody cares of what you do in the inner blocks. Problems Readability Solutions Refactor Sample Code Wrong try {
    transaction.commit();
} catch (e) {
    logerror(e);
    if (e instanceOf DBError){
      try {
          transaction.rollback();
      } catch (e) {
          doMoreLoggingRollbackFailed(e);
      }
    }
}

//Nested Try catchs
//Exception cases are 
//more important than happy path
//We use exceptions as control flow Right try {
    transaction.commit();
} catch (transactionError) {
    this.withTransactionErrorDo(
        transationError, transaction);
}

//transaction error policy is not defined in this function
//so we don't have repeated code
//code is more readable
//It is up to the transaction
//and the error to decide what to do Detection We can detect this smell using parsing trees. Tags Exceptions Conclusion Don't abuse exceptions, don't create Exception classes no one will ever catch, and don't be prepared for every case (unless you have a good real scenario with a covering test). Happy path should always be more important than exception cases. Relations Code Smell 73 - Exceptions for Expected Cases Code Smell 26 - Exceptions Polluting More Info Nested Try/Catchs Credits Photo by on David Clode Unsplash Thanks to @ for his inspiration Rodrigo Tweet Writing software as if we are the only person that ever has to comprehend it is one of the biggest mistakes and false assumptions that can be made. Karolina Szczur And that’s all for now… The next article will explain 5 more code smells!

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