diff --git a/bwt/bwt.go b/bwt/bwt.go
index 577bb485..447443a4 100644
--- a/bwt/bwt.go
+++ b/bwt/bwt.go
@@ -328,9 +328,9 @@ func (bwt BWT) lookupSkipByOffset(offset int) skipEntry {
 		panic(msg)
 	}
 
-	for i := range bwt.firstColumnSkipList {
-		if bwt.firstColumnSkipList[i].openEndedInterval.start <= offset && offset < bwt.firstColumnSkipList[i].openEndedInterval.end {
-			return bwt.firstColumnSkipList[i]
+	for skipIndex := range bwt.firstColumnSkipList {
+		if bwt.firstColumnSkipList[skipIndex].openEndedInterval.start <= offset && offset < bwt.firstColumnSkipList[skipIndex].openEndedInterval.end {
+			return bwt.firstColumnSkipList[skipIndex]
 		}
 	}
 	panic("figure out what to do here")
diff --git a/bwt/bwt_test.go b/bwt/bwt_test.go
index c3fc7c16..cb835c05 100644
--- a/bwt/bwt_test.go
+++ b/bwt/bwt_test.go
@@ -1,6 +1,7 @@
 package bwt
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -323,3 +324,89 @@ func TestBWTReconstruction(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func TestBWTStartError(t *testing.T) {
+	testStr := "banana"
+
+	bwt, err := New(testStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = bwt.Extract(-1, 6)
+	if err == nil {
+		t.Fatal("expected error but got nil")
+	}
+}
+func TestBWT_GetFCharPosFromOriginalSequenceCharPos_Panic(t *testing.T) {
+	testStr := "banana"
+	bwt, err := New(testStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Call the function with an invalid original position
+	originalPos := -1
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("Expected panic, but it did not occur")
+		}
+	}()
+	bwt.getFCharPosFromOriginalSequenceCharPos(originalPos)
+}
+func TestBWT_LFSearch_InvalidChar(t *testing.T) {
+	testStr := "banana"
+	bwt, err := New(testStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pattern := "x" // Invalid character
+
+	result := bwt.lfSearch(pattern)
+
+	if result.start != 0 || result.end != 0 {
+		t.Fatalf("Expected search range to be (0, 0), but got (%d, %d)", result.start, result.end)
+	}
+}
+func TestBWT_LookupSkipByOffset_PanicOffsetExceedsMaxBound(t *testing.T) {
+	testStr := "banana"
+	bwt, err := New(testStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	offset := bwt.getLenOfOriginalStringWithNullChar()
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("Expected panic, but it did not occur")
+		}
+	}()
+	bwt.lookupSkipByOffset(offset)
+}
+
+func TestBWT_LookupSkipByOffset_PanicOffsetExceedsMinBound(t *testing.T) {
+	testStr := "banana"
+	bwt, err := New(testStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	offset := -1
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("Expected panic, but it did not occur")
+		}
+	}()
+	bwt.lookupSkipByOffset(offset)
+}
+
+func TestBWTRecovery(t *testing.T) {
+	// Test panic recovery for bwtRecovery function
+	err := fmt.Errorf("test error")
+	operation := "test operation"
+	defer bwtRecovery(operation, &err)
+
+	panic("test panic")
+	t.Errorf("Expected panic, but it did not occur")
+}
diff --git a/bwt/wavelet_test.go b/bwt/wavelet_test.go
index ac028988..432f4a85 100644
--- a/bwt/wavelet_test.go
+++ b/bwt/wavelet_test.go
@@ -260,3 +260,26 @@ func TestWaveletTreeSingleAlpha(t *testing.T) {
 		t.Fatalf("expected Access(%d) to be %d but got %d", 1, 1, s)
 	}
 }
+func TestBuildWaveletTree_ZeroAlpha(t *testing.T) {
+	bytes := []byte("AAAACCCCTTTTGGGG")
+	alpha := []charInfo{}
+
+	root := buildWaveletTree(0, alpha, bytes)
+
+	if root != nil {
+		t.Fatalf("expected root to be nil but got %v", root)
+	}
+}
+func TestWaveletTree_LookupCharInfo_Panic(t *testing.T) {
+	wt := waveletTree{
+		alpha: []charInfo{},
+	}
+
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("expected panic but got nil")
+		}
+	}()
+
+	wt.lookupCharInfo('B')
+}