Re: How to test value objects when they have dependencies?

Pragmatic answer?
Leave as it is.

You are using absolutely side-effect free "service" objects, that purely 
do calculations and comparisons and have no state (like any good service 
should - or must?).

They are so simple that one may ask why not write them yourself?
And how would you use a own class like those, wouldn't it be the same 
way, without injections?

I do inject only services that are dependent on something lese, e.g. an 
infrastructure or another services, and are not guaranteed to be 
side-effect free.

Just my 0.02$




Am 08.03.2014 02:22, schrieb [email protected]:
>
>
> **TL;DR**
> How do you test a value object in isolation from its dependencies
> without stubbing or injecting them?
>
>
> ----------
>
>
> In Misko Hevery's blog post [To “new” or not to “new”…][1] he advocates
> the following (quoted from the blog post):
>
>  > - An Injectable class can ask for other Injectables in its
> constructor.(Sometimes I refer to Injectables as Service Objects, but
>  > that term is overloaded.). Injectable can never ask for a
> non-Injectable (Newable) in its constructor.
>  > - Newables can ask for other Newables in their constructor, but not
> for Injectables (Sometimes I refer to Newables as Value Object, but
>  > again, the term is overloaded)
>
> Now if I have a `Quantity` value object like this:
>
> class Quantity{
> $quantity=0;
> public function __construct($quantity){
> $intValidator = new Zend_Validate_Int();
> if(!$intValidator->isValid($quantity)){
> throw new Exception("Quantity must be an integer.");
> }
> $gtValidator = new Zend_Validate_GreaterThan(0);
> if(!$gtvalidator->isValid($quantity)){
> throw new Exception("Quantity must be greater than zero.");
> }
> $this->quantity=$quantity;
> }
> }
>
> My `Quantity` value object depends on at least 2 validators for its
> proper construction. Normally I would have injected those validators
> through the constructor, so that I can **stub** them during testing.
>
> However, according to Misko a newable shouldn't ask for injectables in
> its constructor. Frankly a `Quantity` object that looks like this
> `$quantity=new Quantity(1,$intValidator,$gtValidator);` looks really
> awkward.
>
> Using a dependency injection framework to create a value object is even
> more awkward. However now my dependencies are hard coded in the
> `Quantity` constructor and I have no way to alter them if the business
> logic changes.
>
> How do you design the value object properly for testing and adherence to
> the separation between injectables and newables?
>
> Notes:
>
> 1. This is just a very very simplified example. My real object my have
> serious logic in it that may use other dependencies as well.
> 2. I used a PHP example just for illustration. Answers in other
> languages are appreciated.
>
> [1]: http://misko.hevery.com/2008/09/30/to-new-or-not-to-new/
> 



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