Fix a test failure and minitest warnings

lib/execjs/mini_racer_runtime.rb

@@ -6,6 +6,7 @@ class Context < Runtime::Context
       def initialize(runtime, source = "", options={})
         source = encode(source)
         @context = ::MiniRacer::Context.new
+        @context.eval("delete this.console");
         translate do
           @context.eval(source)
         end

test/test_execjs.rb

@@ -104,21 +104,21 @@ def test_context_call_missing_function
     '"\\\\"' => "\\"
   }.each_with_index do |(input, output), index|
     define_method("test_exec_string_#{index}") do
-      assert_equal output, ExecJS.exec("return #{input}")
+      assert_output output, ExecJS.exec("return #{input}")
     end
 
     define_method("test_eval_string_#{index}") do
-      assert_equal output, ExecJS.eval(input)
+      assert_output output, ExecJS.eval(input)
     end
 
     define_method("test_compile_return_string_#{index}") do
       context = ExecJS.compile("var a = #{input};")
-      assert_equal output, context.eval("a")
+      assert_output output, context.eval("a")
     end
 
     define_method("test_compile_call_string_#{index}") do
       context = ExecJS.compile("function a() { return #{input}; }")
-      assert_equal output, context.call("a")
+      assert_output output, context.call("a")
     end
   end
 
@@ -145,25 +145,25 @@ def test_context_call_missing_function
     json_value = JSON.generate(value, quirks_mode: true)
 
     define_method("test_json_value_#{index}") do
-      assert_equal value, JSON.parse(json_value, quirks_mode: true)
+      assert_output value, JSON.parse(json_value, quirks_mode: true)
     end
 
     define_method("test_exec_value_#{index}") do
-      assert_equal value, ExecJS.exec("return #{json_value}")
+      assert_output value, ExecJS.exec("return #{json_value}")
     end
 
     define_method("test_eval_value_#{index}") do
-      assert_equal value, ExecJS.eval("#{json_value}")
+      assert_output value, ExecJS.eval("#{json_value}")
     end
 
     define_method("test_strinigfy_value_#{index}") do
       context = ExecJS.compile("function json(obj) { return JSON.stringify(obj); }")
-      assert_equal json_value, context.call("json", value)
+      assert_output json_value, context.call("json", value)
     end
 
     define_method("test_call_value_#{index}") do
       context = ExecJS.compile("function id(obj) { return obj; }")
-      assert_equal value, context.call("id", value)
+      assert_output value, context.call("id", value)
     end
   end
 
@@ -421,4 +421,14 @@ def test_uglify
     assert_equal "function foo(bar){return bar}",
       context.call("uglify", "function foo(bar) {\n  return bar;\n}")
   end
+
+  private
+
+    def assert_output(expected, actual)
+      if expected.nil?
+        assert_nil actual
+      else
+        assert_equal expected, actual
+      end
+    end
 end