diff --git a/nuke_extra_test.go b/nuke_extra_test.go
new file mode 100644
index 0000000..e2597eb
--- /dev/null
+++ b/nuke_extra_test.go
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package nuke
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"testing"
+	"time"
+	"unsafe"
+
+	"github.com/stretchr/testify/require"
+)
+
+// failingArena always fails to allocate memory.
+type failingArena struct{}
+
+func (f *failingArena) Alloc(size, alignment uintptr) unsafe.Pointer {
+	return nil
+}
+
+func (f *failingArena) Reset(release bool) {
+	// No-op.
+}
+
+// TestNewNilArena verifies that New[T] returns a new pointer using Go's built-in allocation when a nil arena is provided.
+func TestNewNilArena(t *testing.T) {
+	p := New[int](nil)
+	require.NotNil(t, p, "New with nil arena must not return nil")
+	*p = 42
+	require.Equal(t, 42, *p)
+}
+
+// TestMakeSliceNilArena verifies that MakeSlice[T] correctly creates a slice when a nil arena is provided.
+func TestMakeSliceNilArena(t *testing.T) {
+	s := MakeSlice[int](nil, 3, 5)
+	require.Equal(t, 3, len(s))
+	require.Equal(t, 5, cap(s))
+
+	// Test that the slice works as expected.
+	s[0] = 10
+	s[1] = 20
+	s[2] = 30
+	require.Equal(t, []int{10, 20, 30}, s[:3])
+}
+
+// TestMakeSliceAllocFail verifies that when a non-nil arena fails to allocate memory (returns nil),
+// MakeSlice falls back to using Go's built-in make function.
+func TestMakeSliceAllocFail(t *testing.T) {
+	arena := &failingArena{}
+	s := MakeSlice[int](arena, 4, 8)
+	require.Equal(t, 4, len(s))
+	require.Equal(t, 8, cap(s))
+
+	// Write and read some values to ensure the slice works as expected.
+	s[0] = 7
+	s[1] = 14
+	require.Equal(t, 7, s[0])
+	require.Equal(t, 14, s[1])
+}
+
+// TestContextArena verifies that an arena can be injected into and extracted from a context.
+func TestContextArena(t *testing.T) {
+	var arena Arena = &mockArena{}
+	ctx := InjectContextArena(context.Background(), arena)
+	extractedArena := ExtractContextArena(ctx)
+	require.Equal(t, arena, extractedArena, "Extracted arena should match the one injected")
+}
+
+// TestExtractContextArenaNoValue verifies that extracting an arena from a context that has none returns nil.
+func TestExtractContextArenaNoValue(t *testing.T) {
+	arena := ExtractContextArena(context.Background())
+	require.Nil(t, arena, "Extracting arena from context without one should return nil")
+}
+
+// TestConcurrentArena verifies that the concurrent arena correctly wraps a base arena and handles allocations and reset.
+func TestConcurrentArena(t *testing.T) {
+	base := &mockArena{}
+	arena := NewConcurrentArena(base)
+
+	// Run concurrent allocations.
+	const goroutines = 10
+	const iter = 100
+	var wg sync.WaitGroup
+	wg.Add(goroutines)
+	for i := 0; i < goroutines; i++ {
+		go func() {
+			for j := 0; j < iter; j++ {
+				ptr := arena.Alloc(16, 8)
+				require.NotNil(t, ptr, "Allocation in concurrent arena should not be nil")
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+
+	// Test that Reset does not panic.
+	require.NotPanics(t, func() {
+		arena.Reset(true)
+		arena.Reset(false)
+	})
+}
+
+// TestSliceAppendNilArena verifies that SliceAppend works correctly when no arena is provided.
+func TestSliceAppendNilArena(t *testing.T) {
+	original := []int{1, 2, 3}
+	appended := SliceAppend[int](nil, original, 4, 5)
+	require.Equal(t, []int{1, 2, 3, 4, 5}, appended)
+}
+
+// TestGrowSliceWithArena tests the slice growth path when using an arena.
+// It uses a mock arena to exercise the reallocation path in growSlice.
+func TestGrowSliceWithArena(t *testing.T) {
+	a := &mockArena{}
+
+	// Start with a non-empty slice; then append more elements than the current capacity.
+	s := MakeSlice[int](a, 2, 2)
+	s[0] = 100
+	s[1] = 200
+
+	// Append several elements to force a growth.
+	result := SliceAppend[int](a, s, 300, 400, 500)
+	expected := []int{100, 200, 300, 400, 500}
+	require.Equal(t, expected, result)
+}
+
+// TestGrowSliceEmpty exercises the branch in growSlice when the original slice has zero capacity.
+// Instead of using MakeSlice (which would call arena.Alloc with zero size and panic),
+// we start with a nil slice.
+func TestGrowSliceEmpty(t *testing.T) {
+	a := &mockArena{}
+	var s []int // nil slice: len(s)==0 and cap(s)==0
+	s = SliceAppend[int](a, s, 42)
+	require.Equal(t, []int{42}, s)
+	require.Equal(t, 1, cap(s))
+}
+
+// TestSliceAppendNoGrow verifies that when appending data to a slice
+// that already has sufficient capacity, no reallocation is performed.
+func TestSliceAppendNoGrow(t *testing.T) {
+	a := &mockArena{}
+	// Create a slice using the arena with length 3 and capacity 5.
+	s := MakeSlice[int](a, 3, 5)
+	s[0] = 1
+	s[1] = 2
+	s[2] = 3
+	// Append one element; total length becomes 4 which is <= cap(s)==5.
+	s = SliceAppend[int](a, s, 4)
+	require.Equal(t, []int{1, 2, 3, 4}, s[:4])
+	require.Equal(t, 5, cap(s))
+}
+
+// TestGrowSliceLarge verifies the branch in growSlice when the existing slice capacity is large.
+// This forces the new capacity to be increased by newCap + newCap/4.
+func TestGrowSliceLarge(t *testing.T) {
+	a := &mockArena{}
+	// Create a slice with length 150 and capacity 300.
+	s := MakeSlice[int](a, 150, 300)
+	// Initialize the slice so that copy works correctly.
+	for i := 0; i < 150; i++ {
+		s[i] = i
+	}
+	// Append 200 elements, forcing newLen=350, which is >300.
+	data := make([]int, 200)
+	for i := 0; i < 200; i++ {
+		data[i] = 1000 + i
+	}
+	result := SliceAppend[int](a, s, data...)
+	// New capacity should be increased via the "else" branch in growSlice.
+	require.Equal(t, 350, len(result))
+	require.True(t, cap(result) > 300, "new capacity should be increased from original")
+	// Verify contents: first 150 values should be preserved.
+	for i := 0; i < 150; i++ {
+		require.Equal(t, i, result[i])
+	}
+	// The appended data should be present.
+	for i := 0; i < 200; i++ {
+		require.Equal(t, 1000+i, result[150+i])
+	}
+}
+
+// TestMultipleAllocations verifies that using New[T] consecutively from a monotonic arena returns valid pointers,
+// and that when the arena is exhausted, allocations fall back to the heap.
+func TestMultipleAllocations(t *testing.T) {
+	// Create a low-capacity monotonic arena so that after a couple of allocations,
+	// one allocation will return nil from the arena causing New[T] to fall back to heap allocation.
+	arena := NewMonotonicArena(2*int(unsafe.Sizeof(int(0))), 1)
+	p1 := New[int](arena)
+	p2 := New[int](arena)
+	p3 := New[int](arena)
+
+	// p1 and p2 should be allocated from the arena.
+	require.True(t, isMonotonicArenaPtr(arena, unsafe.Pointer(p1)))
+	require.True(t, isMonotonicArenaPtr(arena, unsafe.Pointer(p2)))
+	// p3 might be allocated on the heap if the arena is exhausted.
+	ptrFromArena := isMonotonicArenaPtr(arena, unsafe.Pointer(p3))
+	t.Logf("p3 allocation from monotonic arena: %v", ptrFromArena)
+}
+
+// TestMonotonicArenaReset_NoAlloc tests the Reset method on a monotonic arena that has not yet performed any allocations,
+// ensuring that the early exit branch in reset (when s.offset == 0) is executed.
+func TestMonotonicArenaReset_NoAlloc(t *testing.T) {
+	arena := NewMonotonicArena(1024, 1).(*monotonicArena)
+	// Without any allocation, call Reset with both parameters.
+	require.NotPanics(t, func() { arena.Reset(false) })
+	require.NotPanics(t, func() { arena.Reset(true) })
+}
+
+// TestMonotonicArenaReset_WithAlloc exercises Reset after an allocation has occurred.
+func TestMonotonicArenaReset_WithAlloc(t *testing.T) {
+	arena := NewMonotonicArena(1024, 1).(*monotonicArena)
+	// Allocate an object.
+	_ = New[int](arena)
+	// Reset without releasing memory.
+	require.NotPanics(t, func() { arena.Reset(false) })
+	// Do another allocation.
+	_ = New[int](arena)
+	// Reset with release.
+	require.NotPanics(t, func() { arena.Reset(true) })
+
+	// Wait briefly to allow any asynchronous finalizer activity (if any).
+	time.Sleep(10 * time.Millisecond)
+}
+
+// TestMonotonicArenaAllocFail covers the branch in monotonicArena.Alloc when allocation fails.
+// It requests more memory than is available in the arena.
+func TestMonotonicArenaAllocFail(t *testing.T) {
+	// Create a very small monotonic arena.
+	arena := NewMonotonicArena(64, 1)
+	// Request an allocation larger than the buffer.
+	ptr := arena.Alloc(128, 1)
+	require.Nil(t, ptr, "Allocation should fail and return nil when arena is exhausted")
+}
+
+// Extra benchmark tests (they do not affect coverage).
+func BenchmarkExtra(b *testing.B) {
+	arena := NewMonotonicArena(32*1024*1024, 6)
+	a := newArenaAllocator[int](arena)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = a.new()
+	}
+}
+
+func BenchmarkConcurrentExtra(b *testing.B) {
+	arena := NewConcurrentArena(NewMonotonicArena(32*1024*1024, 6))
+	a := newArenaAllocator[int](arena)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = a.new()
+	}
+}
+
+func BenchmarkRuntimeExtra(b *testing.B) {
+	a := newRuntimeAllocator[int]()
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = a.new()
+	}
+}
+
+func BenchmarkSliceAppendExtra(b *testing.B) {
+	s := []int{}
+	for i := 0; i < b.N; i++ {
+		s = SliceAppend[int](nil, s, i)
+	}
+	// This benchmark is solely to exercise the slice logic.
+	fmt.Println(s[len(s)-1])
+}