feat: add boot self-tests for various kernel components

- Implemented a self-test runner in `selftest.cc` to invoke all test suites.
- Added tests for atomic operations in `test_atomic.cc`, covering construction, store/load, exchange, arithmetic, and compare-and-swap.
- Created tests for the Flattened Device Tree (FDT) in `test_fdt.cc`, verifying node access and compatibility queries.
- Developed a comprehensive Physical Memory Manager (PMM) test suite in `test_pmm.cc`, including allocation, deallocation, reference counting, and boundary conditions.
- Implemented Red-Black Tree tests in `test_rbtree.cc`, validating insertion, deletion, and iteration.
- Added Slab Allocator tests in `test_slab.cc`, covering various allocation sizes, edge cases, and operator overloads.
- Created Spinlock tests in `test_spinlock.cc`, ensuring proper locking behavior and interrupt state preservation.
- Developed Virtual Memory Area (VMA) tests in `test_vma.cc`, validating region mapping, unmapping, and fault handling.
- Added tests for Virtual Memory Management (VMM) in `test_vmm.cc`, verifying address translation and page alignment.

1 files changed, 50 insertions, 0 deletions

diff --git a/na/test/test_fdt.cc b/na/test/test_fdt.cc
new file mode 100644
index 0000000..cf09029
--- /dev/null
+++ b/na/test/test_fdt.cc
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * Boot Self-Test: FDT (Flattened Device Tree)
+ */
+
+#include <lume/selftest.h>
+#include <lume/fdt.h>
+
+// Manually declare what we need to avoid header conflicts with toolchain libc
+extern "C" int strcmp(const char *s1, const char *s2);
+
+void selftest_fdt() {
+    st_begin("fdt: tree root access");
+    {
+        DeviceNode* root = fdt_get_node_by_path("/");
+        ST_ASSERT(root != nullptr);
+        ST_ASSERT_EQ(strcmp(root->get_name(), ""), 0); 
+    }
+    st_pass();
+
+    st_begin("fdt: find existing compatible node (UART)");
+    {
+        // QEMU virt RISC-V platform always has a ns16550a UART
+        DeviceNode* uart = fdt_find_compatible("ns16550a");
+        ST_ASSERT(uart != nullptr);
+        
+        // Use get_prop_string which is convenience helper
+        const char* compat = uart->get_prop_string("compatible");
+        ST_ASSERT(compat != nullptr);
+        
+        // Check raw property access
+        const FdtProperty* reg = uart->get_prop("reg");
+        ST_ASSERT(reg != nullptr);
+        ST_ASSERT(reg->value != nullptr);
+        ST_ASSERT(reg->len > 0);
+    }
+    st_pass();
+
+    st_begin("fdt: non-existent node/compatible queries");
+    {
+        DeviceNode* missing1 = fdt_get_node_by_path("/definitely_does_not_exist_node_12345");
+        ST_ASSERT(missing1 == nullptr);
+
+        DeviceNode* missing2 = fdt_find_compatible("invalid_compatible_string_xyz");
+        ST_ASSERT(missing2 == nullptr);
+    }
+    st_pass();
+}