Mark Gilbert's Blog

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Test-Driven Home Repair

Over the last year, our fluorescent kitchen light was starting to show signs of wear.  Some mornings it would take several minutes to fully turn on.  In January, it started turning on and off on its own.  Then it stopped working altogether.

CJ and I opted for an LED replacement light that had the same footprint as the fluorescent – that way, any unseemly holes or scars that emerged when I took the old light down would at least be covered up when I installed the new one.

Now, does everyone remember what the first step is when working on something electrical?  Make sure you don’t have power running through the lines.

Downstairs I went, to the breaker box.  I had visions of multiple trips up and down, trying to find exactly the right breaker, but incredibly, there was one marked "Kitchen Lt".  I turned it off, and went back up.  I unwrapped the electrical leads to the light – taking care to not touch any of the exposed copper – and tested them.  The indicator light on my tester stayed dark, so that meant no power.  I can proceed, right?

Not so fast.  While I’m relatively comfortable working on the electrical fixtures in my house, I’m also fairly paranoid about it.  After all, I only do something like this maybe twice a year.  How could I tell if the power was REALLY out?

I’d turn the breaker back on, see that the light on my tester actually lit up, turn the breaker off again, and see that it went out.  In other words, test-driven home repair.  I needed to write a failing test – touch the tester to the wires and see the indicator light come up.  Then I would write code to pass that test – turn off the breaker, and the indicator light should go dark.

Another trip the breaker box.  Another trip back upstairs.  Another test of the wires.

The light on my tester was STILL dark.


Do I have a bad tester?  I plugged it into the nearest electrical outlet, and the indicator light came right on.

Um.  Now what? 

With the breaker on, there should be power running through these wires.  Is it possible that I have a break somewhere in the junction box that this light hangs from?  Is there a break in the wires leading from that junction box back to the breaker?  Suddenly, I’m feeling way less confident in my ability to switch out this light.  CJ and I discussed a couple of possibilities, but we decided that if I wasn’t confident enough to finish this job, we’d just have to call in a professional electrician.  I covered up the bare ends (again, taking great care not to touch the copper), and feeling a little dejected and more than a little puzzled.


After a good night’s sleep, CJ figured out the missing piece.  She caught me this morning asked, "You turned off the breaker, but did you…" – and that was all that I needed.  This is a light, Mark.  A kitchen light… with a switch of its own.

Forehead?  Meet wall.

I toggled the power at the breaker, but the light switch on the wall had been off the entire time.  OF COURSE there wouldn’t be any power running through it.

I pulled my tools back up to the kitchen; uncovered the ends; turned on the light switch.  The indicator light on my tester lit right up.  Sigh.  10 minutes later, I had the new light mounted and working*.

While this was another in a long line of "duh" moments for me in the home-improvement space, I was very glad I insisted on getting a failing test before proceeding.  In my day job, not being that disciplined means bugs or bad assumptions can make it through.  When I’m working with 110V, though…

Yeah, you get the picture.


* For the record: 144 LEDs are bright!  CJ says without the cover, the light makes it look like Vegas in our kitchen.  🙂

March 13, 2016 Posted by | Agile | Comments Off on Test-Driven Home Repair