UnitTests: Add tests for WorkQueueThread.

Source/UnitTests/Common/WorkQueueThreadTest.cpp

@@ -0,0 +1,53 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <gtest/gtest.h>
+
+#include "Common/WorkQueueThread.h"
+
+TEST(WorkQueueThread, Simple)
+{
+  Common::WorkQueueThreadSP<int> worker;
+
+  constexpr int BIG_VAL = 1000;
+
+  int x = 0;
+  const auto func = [&](int value) { x = value; };
+
+  worker.Push(1);
+  worker.WaitForCompletion();
+  // Still zero because it's not running.
+  EXPECT_EQ(x, 0);
+
+  // Does nothing if not running.
+  worker.Shutdown();
+
+  worker.Reset("test worker", func);
+  worker.WaitForCompletion();
+  // Items pushed before Reset are processed.
+  EXPECT_EQ(x, 1);
+
+  worker.Shutdown();
+  worker.Push(0);
+  worker.WaitForCompletion();
+  // Still 1 because it's no longer running.
+  EXPECT_EQ(x, 1);
+
+  worker.Cancel();
+  worker.Reset("test worker", func);
+  worker.WaitForCompletion();
+  // Still 1 because the work was canceled.
+  EXPECT_EQ(x, 1);
+
+  for (int i = 0; i != BIG_VAL; ++i)
+    worker.Push(i);
+  worker.Cancel();
+  // Could be any one of the pushed values.
+  EXPECT_LT(x, BIG_VAL);
+  GTEST_LOG_(INFO) << "Canceled work after item " << x;
+
+  worker.Push(2);
+  worker.WaitForCompletion();
+  // Still running after cancelation.
+  EXPECT_EQ(x, 2);
+}