User Stories Should Be *Independent*
by Kelly Waters
In my last entry, I quoted the 'Invest' acronym as a possible way to remember and assess whether or not User Stories are good.The *I* in 'Invest' stands for Independent. Ideally a User Story would be as small as possible, without making it dependent on other Stories.
I recently posted an Example of a User Story. In the next few entries, I'm going to use the 'Invest' acronym to assess whether or not this example is any good?
So, first, let's take a look at whether it's Independent? Personally I see a problem already. In my example of a User Login story, I included a link for 'Forgotten Password', but this is actually a separate story that isn't covered on the card.
When I did this example, I deliberately didn't include the forgotten password feature, in order to keep the story small and fit it on the card. But I did put the forgotten password link on as a reminder of the related story.
If a developer implemented this story as per the card, the forgotten password feature would be a broken link until the related story was implemented. If the Sprint or iteration had finished with the Login story completed and not the Forgotten Password story, the product would not be shippable. Therefore this is not a good example of a User Story that is Independent.
If, however, I had left the link off of this story, and included it on the Forgotten Password story instead, the Login story could have been implemented in its entirety without reliance on other features that may or may not be completed.
So, unfortunately for me, I've failed on the first test! My example User Story is not Independent and the 'Invest' acronym would have helped me spot that straight away. I wonder how I'll do on the other points?
Kelly.
13 March 2008 20:37
This is pretty tricky, though. After all, moving it to the Forgotten Password story does not make the Forgotten Password story independent. It is relying on the fact that you have a login story already implemented.
13 March 2008 20:54
When I started learning XP a bunch of years back, I got that one too, about independence. The theory is, that the user shall be able to pick and choose any of the ready stories, independently of other stories, when doing the planning game.
Practise has taught me, that this is next to impossible!
The example you give is nice and simple, but real world stories are much harder, if not impossible, to make independent.
At least, that is the experience of mine. Why not just admit, that even though it would be nice with independent stories, it just can't happen?
The times I have tried making independent stories, it has ended up being too far-fetched and seemed "faked".
14 March 2008 08:30
True. Although I guess there's always some level of dependency, as the application won't make sense until a certain number of related stories are implemented.
However, the Login feature would be complete without the link, and incomplete with the link but no feature behind it.
Therefore we're really talking about minimising dependencies rather than eliminating them, and at least allowing *complete* features to go into the build throughout the iteration.
Kelly.
15 March 2008 12:32
Responding to Tech Per...
I'm surprised you say that. I realise, as per my response to Jason above, that it's hard. But I don't think it's quite as impossible as you describe. And I think it's still of value to make it as independent as possible.
Maybe it depends on the application. On a web-based prodct where the UI is made up of web controls, in a widgety style like iGoogle or the new BBC home page, it should be perfectly possible. For other apps maybe not...
Kelly.
15 March 2008 20:54
I'm pretty new to this Agile game, but it seems to me that I read a lot of language like "we prefer conventions over standards" or "as soon as possible but not before". I think Agile is NOT about orthodoxy. So it's not like the I in INVEST is silly because it's impossible. It's just stating that we prefer independence over dependency. Put another way, a user story should be as independent as possible but no more.
It probably sounds like I'm backtracking a bit from my first post, and maybe I am. Like I said, I'm learning.
16 March 2008 09:06
I recently commented on Mike Cohn's blog where I mentioned the rediculous possibility of a user story at function level. Surely even at that extreme they are still not totally independent? User stories by their nature and relationships are grouped - and this should be formalised using a hierarchy of themes. Independence is important because it helps define what group of stories could be deployable - so this could be a useful way to define the lowest level of theme with subsequent higher levels of theme being more natural.A Security theme that has two child themes called Login and Forgot Password - these children could then have their own themes that define groups of stories that could be deployed independently.