diff --git a/cbconvert_test.go b/cbconvert_test.go
index cecba62..165c4fa 100644
--- a/cbconvert_test.go
+++ b/cbconvert_test.go
@@ -1,9 +1,12 @@
 package cbconvert
 
 import (
+	"archive/zip"
 	"fmt"
+	"image"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -100,6 +103,397 @@ func TestThumbnail(t *testing.T) {
 	}
 }
 
+func TestConvertResize(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+	opts.Width = 100
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{"testdata/test.cbz"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, file := range files {
+		if err := conv.Convert(file); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	img := firstPage(t, conv, filepath.Join(tmpDir, "test.cbz"))
+	if got := img.Bounds().Dx(); got != 100 {
+		t.Errorf("resized width: got %d, want 100", got)
+	}
+}
+
+func TestConvertFit(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+	opts.Width = 120
+	opts.Height = 120
+	opts.Fit = true
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{"testdata/test.cbz"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, file := range files {
+		if err := conv.Convert(file); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	img := firstPage(t, conv, filepath.Join(tmpDir, "test.cbz"))
+	w, h := img.Bounds().Dx(), img.Bounds().Dy()
+	if w > 120 || h > 120 {
+		t.Errorf("fit exceeded bounds: got %dx%d, want <= 120x120", w, h)
+	}
+	if w != 120 && h != 120 {
+		t.Errorf("fit did not touch a bound: got %dx%d, want one side == 120", w, h)
+	}
+}
+
+func TestConvertTar(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+	opts.Archive = "tar"
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{"testdata/test.cbz"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, file := range files {
+		if err := conv.Convert(file); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	out := filepath.Join(tmpDir, "test.cbt")
+	list, err := conv.archiveList(out)
+	if err != nil {
+		t.Fatalf("read tar output: %v", err)
+	}
+	if len(list) != 2 {
+		t.Errorf("expected 2 pages in tar output, got %d: %v", len(list), list)
+	}
+}
+
+func TestImageTransforms(t *testing.T) {
+	conv := New(NewOptions())
+
+	f, err := os.Open("testdata/test/00.jpg")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	src, err := conv.imageDecode(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	srcW, srcH := src.Bounds().Dx(), src.Bounds().Dy()
+
+	conv.Opts.Rotate = 90
+	rotated := conv.imageTransform(src)
+	if rotated.Bounds().Dx() != srcH || rotated.Bounds().Dy() != srcW {
+		t.Errorf("rotate 90: got %dx%d, want %dx%d", rotated.Bounds().Dx(), rotated.Bounds().Dy(), srcH, srcW)
+	}
+
+	conv.Opts = NewOptions()
+	conv.Opts.Grayscale = true
+	gray := conv.imageTransform(src)
+	if !isGrayScale(gray) {
+		t.Errorf("grayscale: result is not grayscale")
+	}
+
+	conv.Opts = NewOptions()
+	conv.Opts.Brightness = 20
+	conv.Opts.Contrast = 20
+	adjusted := conv.imageTransform(src)
+	if adjusted.Bounds().Dx() != srcW || adjusted.Bounds().Dy() != srcH {
+		t.Errorf("brightness/contrast changed dimensions: got %dx%d, want %dx%d",
+			adjusted.Bounds().Dx(), adjusted.Bounds().Dy(), srcW, srcH)
+	}
+}
+
+func TestCoverName(t *testing.T) {
+	conv := New(NewOptions())
+
+	tests := []struct {
+		name   string
+		images []string
+		want   string
+	}{
+		{"empty", nil, ""},
+		{"natural sort", []string{"10.jpg", "2.jpg", "1.jpg"}, "1.jpg"},
+		{"cover prefix wins", []string{"01.jpg", "cover.jpg", "02.jpg"}, "cover.jpg"},
+		{"front prefix wins", []string{"01.jpg", "front.png", "00.jpg"}, "front.png"},
+		{"cover suffix wins", []string{"01.jpg", "page_cover.jpg"}, "page_cover.jpg"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := conv.coverName(tt.images); got != tt.want {
+				t.Errorf("coverName(%v) = %q, want %q", tt.images, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCoverDirectory(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{"testdata/test"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 1 {
+		t.Fatalf("expected 1 directory file, got %d", len(files))
+	}
+
+	for _, file := range files {
+		if err := conv.Cover(file); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	if _, err := os.Stat(filepath.Join(tmpDir, "test.jpg")); err != nil {
+		t.Errorf("directory cover not written: %v", err)
+	}
+}
+
+func TestFileType(t *testing.T) {
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"testdata/test.cbz", "ZIP"},
+		{"testdata/test.cbr", "RAR"},
+		{"testdata/test.cb7", "7Z"},
+		{"testdata/test.cbt", "TAR"},
+		{"testdata/test.pdf", "PDF"},
+		{"testdata/test", "DIR"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			if got := FileType(tt.path); got != tt.want {
+				t.Errorf("FileType(%q) = %q, want %q", tt.path, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCombine(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+	opts.OutFile = "merged"
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{"testdata/test.cbz", "testdata/test.cbt"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 2 {
+		t.Fatalf("expected 2 input files, got %d", len(files))
+	}
+
+	if err := conv.Combine(files); err != nil {
+		t.Fatal(err)
+	}
+
+	zr, err := zip.OpenReader(filepath.Join(tmpDir, "merged.cbz"))
+	if err != nil {
+		t.Fatalf("open combined archive: %v", err)
+	}
+	defer zr.Close()
+
+	var names []string
+	for _, f := range zr.File {
+		names = append(names, f.Name)
+	}
+
+	if len(names) != 4 {
+		t.Fatalf("expected 4 pages in combined archive, got %d: %v", len(names), names)
+	}
+
+	// each input is prefixed so identically named pages do not collide
+	var first, second int
+	for _, n := range names {
+		switch {
+		case strings.HasPrefix(n, "0001_"):
+			first++
+		case strings.HasPrefix(n, "0002_"):
+			second++
+		}
+	}
+	if first != 2 || second != 2 {
+		t.Errorf("expected 2 pages from each input, got 0001_=%d 0002_=%d: %v", first, second, names)
+	}
+}
+
+func TestSubfolders(t *testing.T) {
+	page0, err := os.ReadFile("testdata/test/00.jpg")
+	if err != nil {
+		t.Fatal(err)
+	}
+	page1, err := os.ReadFile("testdata/test/01.jpg")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	inDir, err := os.MkdirTemp(os.TempDir(), "cbc-in")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(inDir)
+
+	src := filepath.Join(inDir, "chapters.cbz")
+	buildZip(t, src, []zipEntry{
+		{"chapter1/00.jpg", page0},
+		{"chapter1/01.jpg", page1},
+		{"chapter2/00.jpg", page0},
+		{"chapter2/01.jpg", page1},
+	})
+
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc-out")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := NewOptions()
+	opts.OutDir = tmpDir
+
+	conv := New(opts)
+
+	files, err := conv.Files([]string{src})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, file := range files {
+		if err := conv.Convert(file); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	zr, err := zip.OpenReader(filepath.Join(tmpDir, "chapters.cbz"))
+	if err != nil {
+		t.Fatalf("open output archive: %v", err)
+	}
+	defer zr.Close()
+
+	// without subfolder preservation chapter2/00 overwrites chapter1/00 and only 2 pages survive
+	if len(zr.File) != 4 {
+		var names []string
+		for _, f := range zr.File {
+			names = append(names, f.Name)
+		}
+		t.Fatalf("expected 4 pages from numbered subfolders, got %d: %v", len(zr.File), names)
+	}
+}
+
+func TestMeta(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// operate on a copy so the fixture stays intact
+	data, err := os.ReadFile("testdata/test.cbz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	archive := filepath.Join(tmpDir, "meta.cbz")
+	if err := os.WriteFile(archive, data, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	conv := New(NewOptions())
+
+	conv.Opts = NewOptions()
+	conv.Opts.CommentBody = "hello world"
+	if _, err := conv.Meta(archive); err != nil {
+		t.Fatalf("set comment: %v", err)
+	}
+
+	conv.Opts = NewOptions()
+	conv.Opts.Comment = true
+	got, err := conv.Meta(archive)
+	if err != nil {
+		t.Fatalf("get comment: %v", err)
+	}
+	if got != "hello world" {
+		t.Errorf("comment roundtrip: got %q, want %q", got, "hello world")
+	}
+
+	extra := filepath.Join(tmpDir, "ComicInfo.xml")
+	if err := os.WriteFile(extra, []byte("<ComicInfo/>"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	conv.Opts = NewOptions()
+	conv.Opts.FileAdd = extra
+	if _, err := conv.Meta(archive); err != nil {
+		t.Fatalf("add file: %v", err)
+	}
+	if !archiveHas(t, conv, archive, "ComicInfo.xml") {
+		t.Errorf("added file not found in archive")
+	}
+
+	conv.Opts = NewOptions()
+	conv.Opts.FileRemove = "ComicInfo.xml"
+	if _, err := conv.Meta(archive); err != nil {
+		t.Fatalf("remove file: %v", err)
+	}
+	if archiveHas(t, conv, archive, "ComicInfo.xml") {
+		t.Errorf("removed file still present in archive")
+	}
+}
+
 func TestRecursive(t *testing.T) {
 	inDir, err := os.MkdirTemp(os.TempDir(), "cbc-in")
 	if err != nil {
@@ -152,3 +546,75 @@ func TestRecursive(t *testing.T) {
 		t.Errorf("expected output relative to input root at %s: %v", want, err)
 	}
 }
+
+type zipEntry struct {
+	name string
+	data []byte
+}
+
+func buildZip(t *testing.T, path string, entries []zipEntry) {
+	t.Helper()
+
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	zw := zip.NewWriter(f)
+	for _, e := range entries {
+		w, err := zw.Create(e.name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := w.Write(e.data); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := zw.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func firstPage(t *testing.T, conv *Converter, archive string) image.Image {
+	t.Helper()
+
+	zr, err := zip.OpenReader(archive)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer zr.Close()
+
+	if len(zr.File) == 0 {
+		t.Fatalf("archive %s has no entries", archive)
+	}
+
+	rc, err := zr.File[0].Open()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rc.Close()
+
+	img, err := conv.imageDecode(rc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return img
+}
+
+func archiveHas(t *testing.T, conv *Converter, archive, name string) bool {
+	t.Helper()
+
+	list, err := conv.archiveList(archive)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, n := range list {
+		if n == name {
+			return true
+		}
+	}
+
+	return false
+}