Since I am new to agile and as I understand in agile development + testing + bugfixing etc are done in parallel so I would like to understand :
If my story is developed , tested, all the bugs are resolved i.e. even low bugs then only developer start the coding of another story?
Once all bugs are fixed then only we can submit in UAT or we can submit with open low bugs?
Question is broken from the original question as asked by Mark Phillips and CodeGnome
In the waterfall process, tickets are assigned to individual developers by name. At any given point in time, at a minimum, each developer will be working on one ticket. The developer will typically complete the development, unit test it, check it in and move on to the next ticket. At some pre-determined interval, a build will be taken and thrown over the wall to the testing team. Sometimes each developer may be working on more than one ticket, either because one ticket is blocked or because, in the developer's opinion, it is more convenient to work on related tickets together.
In Scrum, the Sprint backlog is owned by the entire team. They are self-organizing. No one (not even the Scrum Master) tells the Development Team how to turn Product Backlog into Increments of potentially releasable functionality. However, here is the key. Let us say there are 9 stories in the Sprint backlog and midway through the Sprint the team determines that they cannot complete all of the stories. It is better to leave one story totally untouched than to have 3 stories half complete. Given this goal how would you take up stories?
You will keep WIP (Work In Progress) low. However, it won't be very effective for a team of, say, seven people to work on one story at a time. They will be tripping on each other. In practice you might find that working on a maximum of 3 or 4 stories at a time may be effective. You can give any team member the guideline outlined by @zsolt:
When you are done with what you are working on, make every effort to see whether you can assist with any story already in progress.
Start on the next priority new story only if you cannot do above.
Since I am new to agile and as I understand in agile development + testing + bugfixing etc are done in parallel.
No, Agile does not specify HOW you do things. You are talking about specific Agile practices like Scrum, Kanban, or XP at this point. If you use XP you will do a lot of testing, dev, and bug-prevention in parallel. Scrum and Kanban don't really contribute much in this domain.
If my story is developed , tested, all the bugs are resolved i.e. even low bugs then only developer start the coding of another story?
This is a good goal to shoot for, but not always possible. Low bugs are sometimes not worth fixing relative to starting higher priority new story work. Other times you will have a manual QA that detects the defect after you thought your work was done. Work with your PO to make the call of whether its OK to ship a feature with a low bug in order to deliver the next item, or if fixing the low item is more valuable to the customer in the given timeframe.
Once all bugs are fixed then only we can submit in UAT or we can submit with open low bugs?
It depends, work with your product owner (PO) or the customer to see what is desired. Most important is that you openly communicate the presence of low defects in the product so that they can be appropriately prioritized in the backlog of work.
On a side note, UAT is not a requirement of Agile software development. I'd argue UAT is actually a relic of waterfall style development. Practices from XP including TDD and pair programming, along with other concepts like ATDD, BDD, continuous integration, test automation, can all help to eliminate the need for a formal UAT period.
A new Scrum Team member can start on a new user story if the previously started user stories are in the done column (team needs to define definion of done) or cannot assist in any other user stories.
