Using plan-do-study-act to improve testing

Testers and developers can use the Deming Cycle to improve the quality of their testing. The Deming Cycle was initially used in the manufacture of telephones and has had a big influence on software development. The cycle has four steps:

• Plan – plan what you are going to do
• Do – execute the planned work
• Study – what went well, what went wrong, what did you learn?
• Act – act on what you have learned and take this learning into the next planning step

The cycle should be repeated with the knowledge accumulated. 

The Deming Cycle can be described as a flow diagram and the Deming Cycle is shown in the flow diagram above.

This cycle is used by testers and developers in their testing for example in TDD and in exploratory testing.

An example of using the Deming Cycle in testing is Test Driven Development (TDD). Adam Hawkins Small Batches podcast has an episode about the cycle[1], during the episode he describes how the Deming Cycle is used every day in TDD. He describes TDD’s use of the cycle as:

• Plan – write the test
• Do – write the code
• Check – did the test pass?
• Act – green tests refactor, red test repeat loop

How TDD uses the Deming Cycle is shown in the flow diagram below:

Elisabeth Hendrickson’s Test Heuristics sheet[2] includes “Demings Cycle” in its list of resources for testing. She is known for her book “Explore It!” about exploratory testing and it is useful to look at how exploratory testing uses the Deming Cycle:

• Plan – write a test charter
• Do – execute a test
• Study – analyse the result of the test
• Act – act on the result of the test, maybe raise a bug card, re-run the test or make another test

How exploratory testing uses the Deming Cycle is shown in the flow diagram below:

Deming was keen that the cycle was understood as plan-do-study-act and not plan-do-check-act. One of the reasons for this was that if you only checked what had been done you might miss something[3]. The study part of the cycle is important because we need to consider what we have learned from the test before we can decide on our next action. It is also important that we are given time to think about the result of the test, this is because which other tests we execute and how we report on the test depend on how we understand the result of the test.

The Deming Cycle can help us improve our testing because it enables us to study and learn from each test we make.

References:

[1] Adam Hawkins Small Batches podcast: PDCA (Plan-Do-Check-Act)

[2] Elisabeth Hendrickson’s Test Heuristics sheet

[3] Lloyd Dobyns and Clare Crawford-Mason Quality or Else

• Further reading:
  • The PDSA Cycle
  • Out of the Crisis by W. Edwards Deming
• Further viewing (you can log in and view the video for free):
  • What did Deming’s work on quality do for us?
• eLearning:
  • DemingNext