diff --git a/base64/base64_test.v b/base64/base64_test.v
new file mode 100644
index 0000000000..67f985b099
--- /dev/null
+++ b/base64/base64_test.v
@@ -0,0 +1,7 @@
+import base64
+
+fn test_decode() {
+	assert base64.decode('TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=')
+	== 'Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.'
+}
+
diff --git a/builtin/array_test.v b/builtin/array_test.v
new file mode 100644
index 0000000000..a677206759
--- /dev/null
+++ b/builtin/array_test.v
@@ -0,0 +1,138 @@
+import os
+
+const (
+	q = [1, 2, 3]
+	A = 8
+)
+
+fn test_ints() {
+	mut a := [1, 5, 2, 3]
+	assert a.len == 4
+	assert a[0] == 1
+	assert a[2] == 2
+	assert a.last() == 3
+	println(a)
+	a << 4
+	println(a)
+	assert a.len == 5
+	assert a[4] == 4
+	assert a.last() == 4
+	// assert a.contains(4) == true
+	// assert a.contains(777) == false
+	// assert a.str() == '51234'
+	mut s := a.str()
+	assert s == '[1, 5, 2, 3, 4]'
+	// Insert
+	// val := 5
+	// a.insert(1, val)// 1 5 2 3 4
+	s = a.str()
+	assert a[1] == 5
+	assert a.last() == 4
+	// a.sort()
+	s = a.str()
+	assert s == '[1, 5, 2, 3, 4]'
+	// Delete
+	a.delete(0)
+	assert a.str() == '[5, 2, 3, 4]'
+	a.delete(1)
+	assert a.str() == '[5, 3, 4]'
+}
+
+fn test_short() {
+	a := [1, 2, 3]
+	assert a.len == 3
+	assert a.cap == 3
+	assert a[0] == 1
+	assert a[1] == 2
+	assert a[2] == 3
+}
+
+fn test_large() {
+	mut a := [0; 0]
+	for i := 0; i < 10000; i++ {
+		a << i
+	}
+	assert a.len == 10000
+	assert a[234] == 234
+}
+
+struct Chunk {
+	val string
+}
+
+struct K {
+	q []Chunk
+}
+
+fn test_empty() {
+	mut chunks := []Chunk{}
+	a := Chunk{}
+	assert chunks.len == 0
+	chunks << a
+	assert chunks.len == 1
+	chunks = []Chunk{}
+	assert chunks.len == 0
+	chunks << a
+	assert chunks.len == 1
+}
+fn test_push() {
+	mut a := []int
+	a << 1
+	a << 3
+	assert a[1] == 3
+	assert a.str() == '[1, 3]'
+}
+
+fn test_strings() {
+	s := 'hi'
+	if s.contains('i') {
+		// println('$s')
+	}
+	a := ['a', 'b', 'c']
+	assert a.str() == '["a", "b", "c"]'
+	// println(a)
+}
+
+fn test_repeat() {
+	a := [0; 5]
+	// a := [0 x 5]
+	assert a.len == 5
+	assert a[0] == 0 && a[1] == 0 && a[2] == 0 && a[3] == 0 && a[4] == 0
+}
+
+fn test_right() {
+	a := [1, 2, 3, 4]
+	b := a.right(1)
+	assert b[0] == 2
+	assert b[1] == 3
+}
+
+fn test_left() {
+	a := [1, 2, 3]
+	b := a.left(2)
+	assert b[0] == 1
+	assert b[1] == 2
+}
+
+fn test_slice() {
+	a := [1, 2, 3, 4]
+	b := a.slice(2, 4)
+	for val in b {
+		println(val)
+	}
+	assert a.slice(1, 2).len == 1
+	println(a.slice(2, 4))
+}
+
+fn test_push_many() {
+	mut a := [1, 2, 3]
+	b := [4, 5, 6]
+	a._push_many(b.data, b.len)
+	assert a.len == 6
+	assert a[0] == 1
+	assert a[3] == 4
+	assert a[5] == 6
+	println(a)
+}
+
+