Add a IoTester class

tests/io_tester.cpp

@@ -0,0 +1,30 @@
+#include "io_tester.hpp"
+#include "catch.hpp"
+#include <iostream>
+
+/**
+ * Directly test this class here
+ */
+TEST_CASE()
+{
+  {
+    IoTester<std::ostream> out(std::cout);
+    std::cout << "test";
+    CHECK(out.str() == "test");
+  }
+  {
+    IoTester<std::ostream> out(std::cout);
+    CHECK(out.str().empty());
+  }
+}
+
+TEST_CASE()
+{
+  {
+    IoTester<std::istream> is(std::cin);
+    is.set_string("coucou");
+    std::string res;
+    std::cin >> res;
+    CHECK(res == "coucou");
+  }
+}