Add test case for Response (#1557)

Author: iwamot

response_test.go

@@ -41,3 +41,13 @@ func TestResponse_Write_UsesSetResponseCode(t *testing.T) {
 	res.Write([]byte("test"))
 	assert.Equal(t, http.StatusBadRequest, rec.Code)
 }
+
+func TestResponse_Flush(t *testing.T) {
+	e := New()
+	rec := httptest.NewRecorder()
+	res := &Response{echo: e, Writer: rec}
+
+	res.Write([]byte("test"))
+	res.Flush()
+	assert.True(t, rec.Flushed)
+}