Go test failure

math.go

package math

import m "math"

// Finds the minimum value in a slice of numbers
func Min(xs []float64) float64 {
    if len(xs) == 0 {
        return m.NaN()
    }
    min := xs[0]
    for _, v := range xs {
        if v < min {
            min = v
        }
    }
    return min
}

math_test.go

package math

import m "math"
import "testing"

type testpair struct {
    values []float64
    average float64
}

var minTests = []testpair{
    { []float64{1,2}, 1 },
    { []float64{1,1,1,1,1,1}, 1 },
    { []float64{-1,1}, -1 },
    { []float64{}, m.NaN() },
}

func TestMin(t *testing.T) {
    for _, pair := range minTests {
        v := Min(pair.values)
        if v != pair.average {
            t.Error(
                "For", pair.values,
                "expected", pair.average,
                "got", v,
            )
        }
    }
}

Splitting it out like this worked:

var emptySlice = []float64{}
x := Min(emptySlice)
if math.IsNaN(x) != true {
    t.Error("For", emptySlice, "expected", math.NaN(), "got", x)
}