add tests

primes_test.go

@@ -14,6 +14,11 @@ func TestPrimes(t *testing.T) {
 	max := uint64(10000)
 
 	Convey("Between should work", t, func() {
+		Convey("for invalid algorithms", func() {
+			primes := Between(0, max, SieveAlgo(999))
+			So(primes, ShouldResemble, []uint64{})
+		})
+
 		for _, algo := range algos {
 			primes := Between(max, 0, algo)
 			So(len(primes), ShouldEqual, 1229)

sievealgo_test.go

@@ -0,0 +1,14 @@
+package primes
+
+import (
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestSieveAlgo(t *testing.T) {
+	Convey("SieveAlgos should be correct", t, func() {
+		So(EratosthenesAlgo, ShouldEqual, 0)
+		So(EratosthenesAlgo.String(), ShouldEqual, "EratosthenesAlgo")
+	})
+}