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6 minute read - Estimation

How Can I Estimate My Testing?

Jun 28, 2011

Have you had anyone ask you a question about estimation? I get asked these types of questions and I suspect that the person really wants answers about how to communicate and justify their guesses.

I think they hope that some process exists which will accurately and objectively give them a set of numbers. And by using these numbers they can disavow responsibility for the production of them. And no-one will hold them responsible if the objectively produced ’estimate’ does not meet reality.

Well in reality ‘Estimate’ really equals ‘Guess’.

So if you want some strategies:

  • Answer the question you want them to ask
  • Ask how long they want it to take
  • Trust your gut
  • Assumptions, Risks and Issues
  • Track the passage of time

I could add an etc. in there, to alert you to the incompleteness of all of this.

But I won’t.

You should assume incompleteness in my presentation. And map it on to your model to identify the blanks.

What culture do you think you work in?

Do you think you work in a culture where ’estimates’ and ‘actual time’ have become synonyms?

Do ’they’ berate you for continuing to work, after the ’estimated’ length of time has passed?

Well, you have learned that regardless of where the estimate came from ’they’ will still hold you responsible for it.

So you need to develop some beliefs. You need to believe that “estimate equals guess”.

You need to believe that any supporting documentation for your guess does not provide a justification for it, it provides a partial model of the thinking that led to the guess.

‘They’ don’t need to believe any of this.

You need to.

Then your communication will change.

Estimates equals Guesses

All estimates equate to GUESSES.

We don’t know how long things will take.

I’m a pretty good psychic. But even I don’t know.

Sometimes we put a framework around our GUESSES. And that can reveal some of our ASSUMPTIONS. It can reveal what RISKS we have considered. It can reveal what ISSUES we perceive.

The framework reveals part of the model we think we used when creating the GUESS. It helps us explain how we created the GUESS.

But even when we do that, our estimates remain GUESSES.

So what could you do?

Do you try and ’educate’ them?

I don’t.

I’m obnoxious like that.

  • So if you get asked “How long will your testing take?”
    • Don’t say “I will provide you with an estimate for testing.”
    • Say “I don’t know.”
    • The conversation might end there.

You might respond with the question you want them to ask.

  • So if you get asked “How long will your testing take?”
    • ask “Do you mean? If I had to guess, right now, how long I think it will take for you to have enough information that you can decide whether or not you want to release this? If so then…”
    • Yup. I say stuff like that.
    • Because then we start talking about what they really want to know.
    • I don’t think I engage in an education process. I try and communicate so we all work from the same assumptions and understandings.

The test managers among you might feel a little nervous with this. As a test manager I used to feel nervous saying that. So you might ask instead:

“How long do you want it to take?”

We live in a world of deadlines. So guesses often don’t help very much.

By asking “How long do you want it to take?” you can build a plan which tries to maximise the value that you can add as quickly as possible before the deadline. Work on the high value items, risks and issues.

Don’t worry about the guesses. Think about the constraints.

When you ask “How long do you want it to take?” then you can think about how much stuff you might fit into that timescale, does it ‘feel’ right?

Trust Your Gut

What you ‘feel’ can feed into your guessing process.

You can get the whole guessing process over really quickly if you just come up with number.

You won’t have stated any assumptions. You won’t have considered any risks. you won’t have any weighted factors. But you can come up with a number quickly.

And your gut will tell you how you feel about it.

Does it feel right?

More importantly – does it feel wrong? If so, you can:

  • Ask yourself what feels wrong about it. Bam. Now you’re starting to come up with assumptions, risks and issues.
  • Come up with a new ‘better’ guess.

When you immediately decide to come up with a new ‘better’ guess. Then you trusted your gut.

If you ask your questions. You distrusted your gut. So you ask those questions to help you regain your trust in your gut.

Assumptions, Risks, Issues

Why bother with the questions?

Why bother with Assumptions, Risks and Issues?

Well, they help you communicate.

Until you develop the force of personality where you can give a number and have it accepted as a best ‘guess’. You might want to engage in a communication process.

If you do want to communicate then you can explain to people the things you have assumed. e.g.

  • I assumed we deliver a release candidate on day X
  • I assumed we have a clean build with no failing unit tests
  • etc.

You can do the same for risks and issues.

We track the passage of time

If your guess gets shot down and ’they’ convince you into using a shorter guess. Then you can ‘manage’ the on-going process by monitoring for any:

  • negated assumptions
  • change in riskiness of the risks
  • transformation of risks into issues

This may not help in the short term as you simply point out that the correctness of the guess becomes ever less likely.

But you might help build credibility long term by communicating based on your frame of reference.

We track over time, the ‘goodness’ of our progress, and how much distance we appear to have to travel before we reach our end point.

We validate our model over time, by comparing it with the reality that we perceive.

Have you covered everything?


I just want to encourage you to keep it simple.

I think you could waste time on a complicated ’estimation’ process using spreadsheets and lots of factors.

‘They’ might well think they need those spreadsheets. Their process may require those spreadsheets. If so, use the spreadsheets to communicate your model, don’t use them to create the guess.

Of you could:

  • guess,
  • start to do the work,
  • based on how long it currently takes extrapolate forward and…
  • guess again

If you do this then you need more courage.

Swapping a belief of “objective estimation”, for “guesses and underpinning models” takes time.

I will not try to convince you that you should.

I just want to make you aware that you could.