Merge #13

13: test(instance) Use `assert_nil` instead of `assert_equal nil, …` r=Hywan a=Hywan

Minitest emits a warning. This patch fixes that.

Co-authored-by: Ivan Enderlin <ivan.enderlin@hoa-project.net>

tests/instance_test.rb

@@ -104,7 +104,7 @@ def test_call_string
   end
 
   def test_call_void
-    assert_equal nil, Wasmer::Instance.new(self.bytes).exports.void
+    assert_nil Wasmer::Instance.new(self.bytes).exports.void
   end
 
   def test_exports