Vignesh Murugesan's Blog

Hi, I'm currently working as a software developer in the logistics industry in San Francisco.  My aim is to impact billions of people's live for the better and make the world a better place. Cheers, Vignesh

When writing test for state machines, I came across a need for a helper that would all call flow into a path some percentage% of times. Eg: func TestSelfDrivingCar_BasicRun(t *testing.T) { car := NewMockCar(t) car.Start() if (/* 50% probability that this will happen */) { car.SimulateLidarFailure() } else if /* 25% probability that this will happen */ { car.SimulateVisionFailure() } else { /* 25% probability that this will happen*/ car.SimulateGearBoxFailure() } car.VerifySafeTrajectory() } You can write a small Go helper like this: package testutils import ( "math/rand" "time" ) // Odds returns True to pct% number of Check() calls type Odds interface { Check() bool } // odds returns `true` pct% of times type odds struct { randgen *rand.Rand pct int } // NewOdds returns a odds instance with the given percent vaule func NewOdds(pct int) Odds { src := rand.NewSource(time.Now().UnixNano(