diff --git a/tests/pretty_printers.hpp b/tests/pretty_printers.hpp
new file mode 100644
index 0000000..42be33e
--- /dev/null
+++ b/tests/pretty_printers.hpp
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2020 CESNET, https://photonics.cesnet.cz/
+ *
+ * Written by Václav Kubernát <kubernat@cesnet.cz>
+ *
+*/
+
+#include <experimental/iterator>
+#include "parser.hpp"
+namespace std {
+std::ostream& operator<<(std::ostream& s, const Completions& completion)
+{
+    s << std::endl << "Completions {" << std::endl << "    m_completions: ";
+    std::transform(completion.m_completions.begin(), completion.m_completions.end(),
+            std::experimental::make_ostream_joiner(s, ", "),
+            [] (auto it) { return '"' + it + '"'; });
+    s << std::endl << "    m_contextLength: " << completion.m_contextLength << std::endl;
+    s << "}" << std::endl;
+    return s;
+}
+}