Add missing test for ConsoleManager

tests/test_ConsoleManager.cpp

@@ -29,5 +29,13 @@ TEST_CASE("ConsoleManager", "[utils]")
     REQUIRE(rang::rang_implementation::controlMode() == rang::control::Off);
 
     rang::setControlMode(saved_control);
+
+    const bool show_preamble = ConsoleManager::showPreamble();
+
+    ConsoleManager::setShowPreamble(not show_preamble);
+    REQUIRE(show_preamble != ConsoleManager::showPreamble());
+
+    ConsoleManager::setShowPreamble(show_preamble);
+    REQUIRE(show_preamble == ConsoleManager::showPreamble());
   }
 }