Ylan Segal

Experiment: Use RSpec Expectation Syntax

A few months ago, the RSpec team announced the new expectation syntax. In the simplest form, the old way of saying:

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foo.should eq(bar)
foo.should_not eq(bar)

is now:

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expect(foo).to eq(bar)
expect(foo).not_to eq(bar)

Most of my work is on a long-running project with an extensive test suite. It has over 8,000 should statements in it:

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$ ag '\.should' spec | wc -l
    8097

This personal experiment is a simple one: Stop using should. Use expect.

The motivation for the experiment is to not be left behind. The writing is on the wall. Although the RSpec team has not announced the deprecation of the should syntax, it is clear that the prefer the expect syntax and believe this is the way forward.

Methodology

For the last two weeks, I have been writing all new specs exclusively with the expect syntax. At this point, I have made no effort to change all existing uses of should. I have always liked the should syntax for its expressiveness, which I suspected was lacking in expect.

Results

I was pleasantly surprised. At first, I found myself immediately reaching for my trusted should. Pretty quickly expect started to become second nature. I still believe that should is bit more expressive when reading complete lines of code. However, expect does have an advantage: It is usually at the beginning of the line, which makes it obvious which lines are setup for the example and which are the expectations or assertions.

Going Forward

expect is in, should is out for all new specs. There is no immediate intention to convert wholly to expect because the project is large and we can’t immediately move to RSpec 3.x branch anyway (becuause of a conflict with another gem). That will need to come at a later time. In the meantime, we can start converting file by file as we touch them and do the work piecemeal.