AK: Implement AK::Stack

Author: https://github.com/Quaker762
Commit: 2b123cc592
Pull-request: https://github.com/SerenityOS/serenity/pull/7024
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/ccapitalK
Reviewed-by: https://github.com/predmond
Reviewed-by: https://github.com/sunverwerth

Tests/AK/TestStack.cpp

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+
+#include <AK/Stack.h>
+
+TEST_CASE(basic)
+{
+    AK::Stack<int, 3> stack;
+
+    EXPECT(stack.is_empty() == true);
+    stack.push(2);
+    stack.push(4);
+    stack.push(17);
+    EXPECT(stack.size() == 3);
+    EXPECT(stack.top() == 17);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT(stack.is_empty());
+}
+
+TEST_CASE(complex_type)
+{
+    AK::Stack<String, 4> stack;
+
+    EXPECT_EQ(stack.is_empty(), true);
+    EXPECT(stack.push("Well"));
+    EXPECT(stack.push("Hello"));
+    EXPECT(stack.push("Friends"));
+    EXPECT(stack.push(":^)"));
+    EXPECT_EQ(stack.top(), ":^)");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Friends");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Hello");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT_EQ(stack.top(), "Well");
+    EXPECT_EQ(stack.pop(), true);
+    EXPECT(stack.is_empty());
+}