“The ability to work and deliver in small batches is especially important” [1], which is why many development teams work in small batches.
Scrum teams work in small batches by limiting the work they plan to do in a sprint. Kanban teams work in small batches by limiting the work in progress. Working in small batches is one of “the key principles at the heart of continuous delivery”[2], and so teams that practice continuous delivery or continuous deployment work in small batches.
I like a story in The Machine that Changed the World about Taichi Ohno that shows some benefits that Toyota found from working in small batches.[3]
Back in the late 1940’s American car manufacturers used dies to stamp car parts from large sheets of steel using huge presses. Each press worked 24/7 and could produce over a million parts a year. A misalignment in the die would produce wrinkled parts and could result in the need for expensive repairs. Changing a die took a day and was done by a specialist team.[2]
At this time Toyota was a relatively small company. Taichi Ohno had a smaller budget than American car manufacturers, and this meant that he had to stamp virtually the whole car from a few second-hand presses. Through experimenting, by the late 1950s, he found that dies could be changed in three minutes by production line workers without any specialists. Ohno then “made an unexpected discovery- it actually cost less per part to make small batches of stamplings than to run off enormous lots”.[4]
There were two reasons for small batches to be cheaper. One reason was that Toyota did not have to manage a huge inventory of parts and the other reason was that mistakes showed up very quickly.[3]
Working in small batches meant that the workers in the stamping shop became more concerned with quality, and that there were less faulty parts.[4]
Toyota needed a skilled and motivated workforce to implement this system.[4]
I like the story because, despite being such an old story, the points it makes are still relevant today. The Toyota Production System has had a big influence on lean and agile and so has influenced how we work.
I manage my manual testing and test automation in small batches, this enables me to be flexible in how I work and give quick feedback. I merge one automated test at a time into the main branch so I can focus on making it a good-quality test. Working in “small batches” also enables me to be more flexible. If I was automating more than one test and a developer wanted my time they would have to wait. However, as I am automating only one test I can quickly be available to help them.
I work with a team that practices continuous deployment. We deploy in as small a batch as possible by deploying to production each merge to the main branch. We do not have to manage the inventory of a monthly release, faults are detected quickly and as a consequence, customers experience fewer software errors.
References
[1] Accelerate by Nicole Forsgren, PhD, Jez Humble and Gene Kim (2018, p54)
[1] Accelerate by Nicole Forsgren, PhD, Jez Humble and Gene Kim (2018, p71)
[2] The Machine that Changed the World by James P. Womack, Daniel T. Jones and Daniel Roos (1990, p52)
[3] The Machine that Changed the World by James P. Womack, Daniel T. Jones and Daniel Roos(1990, p53)
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