domain/turn_order: fix a round underflow bug

1 files changed, 42 insertions, 0 deletions

diff --git a/domain/tests/turn_order_bugs.cpp b/domain/tests/turn_order_bugs.cpp
new file mode 100644
index 0000000..418a36c
--- /dev/null
+++ b/domain/tests/turn_order_bugs.cpp
@@ -0,0 +1,42 @@
+#include "turns/domain/participant.hpp"
+#include "turns/domain/turn_order.hpp"
+
+#include <catch2/catch_test_macros.hpp>
+
+#include <giomm/liststore.h>
+
+namespace turns::domain::tests
+{
+  /**
+   * Bug description:
+   *
+   * After having stepped according to the step pattern below, tt was possible to step backward often enough to underflow the round number:
+   * - forward
+   * - backward
+   * - forward
+   */
+  SCENARIO("Can step back infinitely", "[turn_order][bug]")
+  {
+    GIVEN("a non-empty turn_order")
+    {
+      auto instance = turn_order::create();
+
+      instance->add("A", 0, disposition::neutral);
+
+      WHEN("it is started and then stepped forward, backward, forward")
+      {
+        instance->start();
+        instance->next();
+        instance->previous();
+        instance->next();
+
+        THEN("it is not possible to step backwards more than once")
+        {
+          instance->previous();
+          instance->previous();
+          REQUIRE(instance->round_number() == 0);
+        }
+      }
+    }
+  }
+}  // namespace turns::domain::tests
\ No newline at end of file