diff --git a/mrbgems/mruby-bigint/test/bigint.rb b/mrbgems/mruby-bigint/test/bigint.rb
new file mode 100644
index 000000000..8ab09548e
--- /dev/null
+++ b/mrbgems/mruby-bigint/test/bigint.rb
@@ -0,0 +1,23 @@
+assert 'Bigint basic' do
+  n = 1<<65
+  assert_equal 36893488147419103232, n
+  assert_equal 36893488147419104229, n+997
+  assert_equal 36893488147419102235, n-997
+  assert_equal 36782807682976845922304, n*997
+  assert_equal 37004501652376231, n.div(997)
+end
+
+assert 'Bigint to_s' do
+  n = 1197857166996989179607278372168909873645893814254642585755536286462800958278984531968
+  assert_equal n, "11978_571669_96989179607278372168909873645893814254642585755536286462800958278984531968".to_i
+  assert_equal(-n, "-11978_571669_96989179607278372168909873645893814254642585755536286462800958278984531968".to_i)
+  n = 0x1197857166996989179607278372168909873645893814254642585755536286462800958278984531968
+  assert_equal n, "1197857166996989179607278372168909873645893814254642585755536286462800958278984531968".to_i(16)
+end
+
+assert 'Bigint pow' do
+  n = 18446744073709551616
+  assert_equal n, 2 ** 64
+  assert_equal n, 1 << 64
+  assert_equal 2, n >> 63
+end