KF-31 Add tests for UStringBuilder

test/CMakeLists.txt

@@ -59,6 +59,7 @@ wdk_add_driver(kf-test WINVER NTDDI_WIN10 STL
     AutoSpinLockTest.cpp
     EResourceSharedLockTest.cpp
     RecursiveAutoSpinLockTest.cpp
+    UStringBuilderTest.cpp
 )
 
 target_link_libraries(kf-test kf::kf kmtest::kmtest)

test/UStringBuilderTest.cpp

@@ -0,0 +1,140 @@
+#include "pch.h"
+#include <kf/UStringBuilder.h>
+#include <kf/UString.h>
+
+using namespace kf;
+
+SCENARIO("UStringBuilder")
+{
+    GIVEN("A default constructed builder")
+    {
+        UStringBuilder<PagedPool> sb;
+
+        THEN("It holds an empty string")
+        {
+            REQUIRE(sb.string().isEmpty());
+            REQUIRE(sb.string().charLength() == 0);
+            REQUIRE(sb.string().maxCharLength() == 0);
+        }
+
+        WHEN("reserve(0) is called")
+        {
+            NTSTATUS status = sb.reserve(0);
+
+            THEN("It succeeds and remains empty")
+            {
+                REQUIRE_NT_SUCCESS(status);
+                REQUIRE(sb.string().isEmpty());
+                REQUIRE(sb.string().maxCharLength() == 0);
+            }
+        }
+
+        WHEN("reserve(10) is called")
+        {
+            NTSTATUS status = sb.reserve(10);
+
+            THEN("Capacity grows and length stays 0")
+            {
+                REQUIRE_NT_SUCCESS(status);
+                REQUIRE(sb.string().charLength() == 0);
+                REQUIRE(sb.string().maxCharLength() == 10);
+            }
+        }
+    }
+
+    GIVEN("An empty builder")
+    {
+        UStringBuilder<PagedPool> sb;
+
+        WHEN("A single PCWSTR is appended")
+        {
+            NTSTATUS status = sb.append(L"abc");
+
+            THEN("The resulting string equals 'abc'")
+            {
+                REQUIRE_NT_SUCCESS(status);
+                REQUIRE(sb.string().charLength() == 3);
+                REQUIRE(sb.string().equals(L"abc"));
+            }
+        }
+
+        WHEN("USimpleString and PCWSTR are appended in sequence")
+        {
+            NTSTATUS status1 = sb.append(L"ab");
+            USimpleString part(L"cd");
+            NTSTATUS status2 = sb.append(part);
+            NTSTATUS status3 = sb.append(L"");
+
+            THEN("They concatenate to 'abcd'")
+            {
+                REQUIRE_NT_SUCCESS(status1);
+                REQUIRE_NT_SUCCESS(status2);
+                REQUIRE_NT_SUCCESS(status3);
+                REQUIRE(sb.string().charLength() == 4);
+                REQUIRE(sb.string().equals(L"abcd"));
+            }
+        }
+
+        WHEN("Variadic append with multiple arguments is used")
+        {
+            USimpleString a(L"ab");
+            USimpleString c(L"cd");
+            NTSTATUS status = sb.append(a, c, L"ef");
+
+            THEN("All parts are appended in order")
+            {
+                REQUIRE_NT_SUCCESS(status);
+                REQUIRE(sb.string().charLength() == 6);
+                REQUIRE(sb.string().equals(L"abcdef"));
+            }
+        }
+
+        WHEN("Multiple append calls trigger internal reallocation and preserve content")
+        {
+            REQUIRE_NT_SUCCESS(sb.append(L"abc"));
+            // Force growth by appending a longer chunk
+            REQUIRE_NT_SUCCESS(sb.append(L"defghij"));
+
+            THEN("Final content is the concatenation of all parts")
+            {
+                REQUIRE(sb.string().charLength() == 10);
+                REQUIRE(sb.string().equals(L"abcdefghij"));
+            }
+        }
+    }
+
+    GIVEN("A builder with content 'Hello'")
+    {
+        UStringBuilder<PagedPool> sb;
+        REQUIRE_NT_SUCCESS(sb.append(L"Hello"));
+
+        WHEN("copyTo is used with a small destination buffer")
+        {
+            WCHAR buf[4] = { 0 };
+            int copied = sb.string().copyTo(buf);
+            THEN("It copies as many chars as fits including null-terminator in destination")
+            {
+                REQUIRE(copied == 3); // min(4-1, 5) = 3
+                REQUIRE(buf[0] == L'H');
+                REQUIRE(buf[1] == L'e');
+                REQUIRE(buf[2] == L'l');
+                REQUIRE(buf[3] == L'\0');
+            }
+        }
+
+        WHEN("reserve is called with a smaller size than current length")
+        {
+            // Note: current charLength is 5, reserve(3) will reallocate to 3 and truncate
+            NTSTATUS status = sb.reserve(3);
+
+            THEN("It truncates the current content")
+            {
+                REQUIRE_NT_SUCCESS(status);
+                REQUIRE(sb.string().charLength() == 3);
+                REQUIRE(sb.string().equals(L"Hel"));
+                REQUIRE(sb.string().maxCharLength() == 3);
+            }
+        }
+    }
+}
+