diff --git a/util/map_test.go b/util/map_test.go
new file mode 100644
index 0000000..949364b
--- /dev/null
+++ b/util/map_test.go
@@ -0,0 +1,29 @@
+package util
+
+import "testing"
+
+func TestMap(t *testing.T) {
+	var tests = []struct {
+		x, inmin, inmax, outmin, outmax int64
+		val                             int64
+	}{
+		{
+			90, 0, 180, 1000, 2000,
+			1500,
+		},
+		{
+			10, 10, 15, 10, 20,
+			10,
+		},
+		{
+			15, 10, 15, 10, 20,
+			20,
+		},
+	}
+	for _, test := range tests {
+		val := Map(test.x, test.inmin, test.inmax, test.outmin, test.outmax)
+		if val != test.val {
+			t.Errorf("Map of %v from (%v -> %v) to (%v -> %v): got %v, want %v", test.x, test.inmin, test.inmax, test.outmin, test.outmax, val, test.val)
+		}
+	}
+}