Don't Skip Trivial Refactorings

Summary: if you are going to use test driven development as your process for implementing new features, and you don't want to just draw the owl, then you need to train yourself to refactor aggressively.

My example today is Tom Oram's 2018-11-11 essay on Uncle Bob's Transformation Priority Premise.  Oram uses four tests and seven distinct implementations of even?

If he were refactoring aggressively, I think we would see three implementations from two tests.

	# Test: expect(even?(1)).to be(false)
	# Transformation: nil -> constant
	# This is Oram's original implementation, unchanged
	def even?(number)
	false
	end
	# Refactor
	# Let's be explicit about why `false` is the correct answer here
	# WITHOUT changing the observable behavior
	def even?(number)
	1 % 2 == 0
	end
	# Test: expect(even?(2)).to be(true)
	# Transformation: constant -> scalar
	# This is Oram's final implementation, unchanged
	def even?(number)
	number % 2 == 0
	end

view raw even.rb hosted with ❤ by GitHub

Kent Beck, in the face of objections to such a refactoring under the auspices of "removing duplication", wrote:

Sorry. I really really really am just locally removing duplication,
data duplication, between the tests and the code. The nicely general formula
that results is a happy accident, and doesn't always appear. More often than
not, though, it does.

No instant mental triangulation. No looking forward to future test cases.
Simple removal of duplication. I get it now that other people don't think
this way. Believe me, I get it. Now I have to decide whether to begin
doubting myself, or just patiently wait for most of the rest of the world to
catch up. No contest--I can be patient.

At that time, Beck was a bit undisciplined with his definition of "refactoring".  Faced with the same problem, my guess is that he would have performed the constant -> scalar transformation during his "refactoring" step.  If there isn't a test, then it's not observable behavior?

Personally, I find that the disciplined approach reduces error rates.