diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index 5a133fd7b7..dcd2218b98 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -356,6 +356,7 @@ fn test_reduce() {
 fn test_filter() {
 	a := [1, 2, 3, 4, 5, 6]
 	b := a.filter(it % 2 == 0)
+	assert b.len == 3
 	assert b[0] == 2
 	assert b[1] == 4
 	assert b[2] == 6
@@ -365,6 +366,20 @@ fn test_filter() {
 	assert d[1] == 'awesome'
 }	
 
+fn test_map() {
+	a := [1, 2, 3, 4, 5, 6]
+	b := a.map(it * 10)
+	assert b.len == 6
+	assert b[0] == 10
+	assert b[1] == 20
+	assert b[2] == 30
+	c := ['v', 'is', 'awesome']
+	d := c.map(it.to_upper())
+	assert d[0] == 'V'
+	assert d[1] == 'IS'
+	assert d[2] == 'AWESOME'
+}	
+
 fn test_array_str() {
 	numbers := [1, 2, 3]
 	numbers2 := [numbers, [4, 5, 6]] // dup str() bug