kernel: add basic bus tests

1 files changed, 104 insertions, 0 deletions

diff --git a/kernel/kapi/devices/bus.tests.cpp b/kernel/kapi/devices/bus.tests.cpp
new file mode 100644
index 00000000..d5a2d1cf
--- /dev/null
+++ b/kernel/kapi/devices/bus.tests.cpp
@@ -0,0 +1,104 @@
+#include <kapi/devices.hpp>
+
+#include <kstd/memory.hpp>
+#include <kstd/string.hpp>
+
+#include <catch2/catch_test_macros.hpp>
+
+namespace
+{
+
+  struct test_bus final : kapi::devices::bus
+  {
+    using kapi::devices::bus::bus;
+  };
+
+  struct test_device final : kapi::devices::device
+  {
+    using kapi::devices::device::device;
+
+    auto init() -> bool override
+    {
+      return true;
+    }
+  };
+
+  struct flagging_device final : kapi::devices::device
+  {
+    flagging_device(kstd::string const & name, bool & destroyed_flag)
+        : device{name}
+        , m_destroyed_flag{&destroyed_flag}
+    {}
+
+    ~flagging_device() override
+    {
+      *m_destroyed_flag = true;
+    }
+
+    auto init() -> bool override
+    {
+      return true;
+    }
+
+  private:
+    bool * m_destroyed_flag;
+  };
+
+}  // namespace
+
+SCENARIO("A bus shares ownership of its children, holding a weak link to its parent", "[devices][bus]")
+{
+  GIVEN("A bus with one attached child device")
+  {
+    auto parent_bus = kstd::make_shared<test_bus>("bus_ownership_parent");
+    auto child = kstd::make_shared<test_device>("bus_ownership_child");
+
+    parent_bus->add_child(child);
+
+    THEN("the child is reachable through children()")
+    {
+      REQUIRE(parent_bus->children().size() == 1);
+      REQUIRE(parent_bus->children()[0]->name() == "bus_ownership_child");
+    }
+
+    THEN("the child's parent resolves back to the bus")
+    {
+      auto locked_parent = child->parent();
+      REQUIRE(locked_parent);
+      REQUIRE(locked_parent->name() == "bus_ownership_parent");
+    }
+
+    WHEN("the bus is destroyed while the caller still holds the child directly")
+    {
+      parent_bus.reset();
+
+      THEN("the child outlives the bus")
+      {
+        REQUIRE(child != nullptr);
+      }
+
+      THEN("the child's parent link no longer resolves")
+      {
+        REQUIRE(child->parent() == nullptr);
+      }
+    }
+  }
+
+  GIVEN("a bus that is the only thing keeping its child alive")
+  {
+    auto destroyed = false;
+    auto parent_bus = kstd::make_shared<test_bus>("bus_lifetime_parent");
+    parent_bus->add_child(kstd::make_shared<flagging_device>("bus_lifetime_child", destroyed));
+
+    WHEN("the bus is destroyed")
+    {
+      CHECK_FALSE(destroyed);
+      parent_bus.reset();
+
+      THEN("the child is destroyed along with it")
+      {
+        REQUIRE(destroyed);
+      }
+    }
+  }
+}