How should a Software Tester deal with missed Defects/bugs in release
I work as a QA/test engineer in a small software company. It is a web based product. I was assigned a few projects by my manager. I mostly do functional/black-box testing. Before the release, I tested many good scenarios and found quite a few defects in the code. Most of them got fixed. I did my analysis and gave important information to the stakeholders. I had a good test strategy at that time. Now, a client found a lot of bugs and the client is disappointed with testing.
So how to improve my testing and cover all test cases?
My manager and the stakeholders don't trust my work as a tester, as how dare I say that it PASS the QA the first time. They think that I'm careless, not worthy of working, and risky.
You will never ever cover all of the possible test cases.
and found quite a few defects in the code. Most of them got fixed.
Were any of the bugs related to these. Did you point out the possible consequences of the ones that were not fixed?
I did my analysis and gave important information to the stakeholders.
Did anyone read it? Did you point out what you did not cover?
Now, client found lot of bug and client disappoint with testing.
Were they in the same area? Was it anything that you could have changed? When told about it, did you realize other things that you could change about how you test?
You were assigned a few small products. I'm guessing that a few bugs were probably found in production, because, well, they always are. The important part is to learn from it. Don't beat yourself up over what you've missed, just learn from it; don't miss the same thing again. Keep doing a good job; build up your reputation in the eyes of your manager and stakeholders again. It may take time. They may not realize the nuances of testing either. It's not like they treat the developer the same way for writing the bug to begin with, are they?
You say that there are managers and stakeholders. Is the client another company? Do they do User Acceptance Testing. Could they take a look at it before it goes live? You're one person, you, or an entire team, will ever catch every possible bug. Just catch the ones you can, learn, and move on.