Which test will fall if we delete this piece of code?

Look, there is an alarm like this:

class Alarm  def to_human    at.strftime("%k:%M").strip  endend

And this test:

it "returns alarm in human-readable 24-hour format" do  time = Time.local(2019, 7, 7, 10, 35)  alarm = described_class.new(at: time)  expect(alarm.to_human).to eq "10:35"end

To see if these tests are enough, I look at the module being tested and ask myself: what would happen, if I remove this piece of code, which expectation will fail? If none, then I'm 100% missing checks or expectations.

In the alarm clock example, the .strip is in question. If you delete it, the test stays green. So the expectation is missing:

it "strips any leading spaces" do  time = Time.local(2019, 7, 7, 7, 15)  alarm = described_class.new(at: time)  expect(alarm.to_human).to eq "7:15"end