When testing makes no sense

Stockholm syndrome

"Premature optimization is the root of all evil"

Donald Knuth

When should we write tests?

High cost to fix?

Cost of fixing > cost of testing

When it brings "value"

Value = benefit - cost

Fallacy #1:

It makes my project more expensive

Do you charge for manual testing?

Bugs cost too

Ask for forgiveness, not permission

Fallacy #2:

It takes a lot of time

learning != using

Fallacy #3:

It takes extra time

Manual testing takes time as well

Fallacy #4:

ship PoC to production

Feature lifecycle

Phase 1: Exploration

Phase 2: Modelling/architecture

Phase 3: Development

Phase 4: Production

Fallacy #5:

100% code coverage

class User
{
...
    function isAdmin() : bool{
        return $this->admin;
    }
...
}

Fallacy #6:

writing tests later is OK

class User
{
...
    function shouldChargeVat() : bool{
        if($this->isCompany()){
            return false;
        }
        return true;
    }
...
}

Fallacy #7:

we have "tests"

Fallacy #8:

TDD has something to do with testing

Easier to add new features

class User
{
...
    function shouldChargeVat() : bool{
        if($this->isCompany()){
            return false;
        }
        return true;
    }
...
}

class User
{
...
    function shouldChargeVat() : bool{
        if(true === $this->isCompany()){
            if('SLO' === $this->country){
                return true;
            }else{
                return false;
            }
        }
        return true;
    }
...
}

Easier refactoring

class User
{
...
    function shouldChargeVat() : bool{
        if(true === $this->isCompany()){
            if('SLO' === $this->country){
                return true;
            }else{
                return false;
            }
        }
        return true;
    }
...
}

class User
{
...
    function shouldChargeVat() : bool{
        if('SLO' === $this->country){
            return true;
        }
        if(true === $this->isCompany()){
            return false;
        }
        return true;
    }
...
}

class User
{
...
    function shouldChargeVat() : bool{
        if('SLO' === $this->country){
            return true;
        }
        if(true === $this->isCompany()){
            return false;
        }
        return true;
    }
...
}

class User
{
...
    function shouldChargeVat() : bool{
        if(true === $this->isCompany()){
            if('SLO' === $this->country){
                return true;
            }else{
                return false;
            }
        }
        return true;
    }
...
}

Cleaner code

It's hard to test

shitty code