inching up coverage.

tick.go

@@ -1,5 +1,17 @@
 package chart
 
+// GenerateTicksWithStep generates a set of ticks.
+func GenerateTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
+	var ticks []Tick
+	for cursor := ra.Min; cursor < ra.Max; cursor += step {
+		ticks = append(ticks, Tick{
+			Value: cursor,
+			Label: vf(cursor),
+		})
+	}
+	return ticks
+}
+
 // Tick represents a label on an axis.
 type Tick struct {
 	Value float64