diff --git a/pkgs/mruby/test/assert.rb b/pkgs/mruby/test/assert.rb
new file mode 100644
index 00000000..5a1b94f7
--- /dev/null
+++ b/pkgs/mruby/test/assert.rb
@@ -0,0 +1,20 @@
+assert 'KernAux.assert_cb is set by default' do
+  assert_equal KernAux::DEFAULT_ASSERT_CB, KernAux.assert_cb
+end
+
+assert 'KernAux::DEFAULT_ASSERT_CB raises' do
+  assert_raise KernAux::AssertError, 'foo.rb:123:bar' do
+    KernAux::DEFAULT_ASSERT_CB.call 'foo.rb', 123, 'bar'
+  end
+end
+
+assert 'we can set KernAux.assert_cb' do
+  KernAux.assert_cb = KernAux::DEFAULT_ASSERT_CB
+  assert_equal KernAux::DEFAULT_ASSERT_CB, KernAux.assert_cb
+end
+
+assert 'KernAux.assert_do raises' do
+  assert_raise KernAux::AssertError, 'foo.rb:123:hello' do
+    KernAux.assert_do 'foo.rb', 123, 'hello'
+  end
+end
diff --git a/pkgs/mruby/test/dummy.rb b/pkgs/mruby/test/dummy.rb
deleted file mode 100644
index d3c77179..00000000
--- a/pkgs/mruby/test/dummy.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-assert do
-  assert_equal KernAux::DEFAULT_ASSERT_CB, KernAux.assert_cb
-
-  KernAux.assert_cb = 123
-  assert_equal 123, KernAux.assert_cb
-
-  KernAux.assert_cb = KernAux::DEFAULT_ASSERT_CB
-  assert_equal KernAux::DEFAULT_ASSERT_CB, KernAux.assert_cb
-
-  assert_raise KernAux::AssertError, 'foo.rb:123:hello' do
-    KernAux.assert_do 'foo.rb', 123, 'hello'
-  end
-end