diff --git a/utils.go b/utils.go
index eb5b689..d806839 100644
--- a/utils.go
+++ b/utils.go
@@ -95,11 +95,15 @@ func ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error) {
 // with a cancelable context.
 func WriteAllContext(ctx context.Context, w io.Writer, data []byte) error {
 	const chunkSize = 4 * 1024 * 1024 // 4MB
+	return writeAllContext(ctx, w, data, chunkSize)
+}
+
+func writeAllContext(ctx context.Context, w io.Writer, data []byte, chunkSize int) error {
 	for len(data) > 0 {
-		if ctx.Err() != nil {
-			return ctx.Err()
+		if err := ctx.Err(); err != nil {
+			return err
 		}
-		n, err := w.Write(data[:max(chunkSize, len(data))])
+		n, err := w.Write(data[:min(chunkSize, len(data))])
 		if err != nil {
 			return err
 		}
diff --git a/utils_test.go b/utils_test.go
new file mode 100644
index 0000000..34b3273
--- /dev/null
+++ b/utils_test.go
@@ -0,0 +1,70 @@
+package fs
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+type failContext struct {
+	errAfter int
+	err      error
+
+	counter int
+}
+
+func (*failContext) Deadline() (deadline time.Time, ok bool) { return time.Time{}, false }
+func (*failContext) Done() <-chan struct{}                   { return nil }
+func (*failContext) Value(key any) any                       { return nil }
+
+func (f *failContext) Err() error {
+	f.counter++
+	if f.counter > f.errAfter {
+		return f.err
+	}
+	return nil
+}
+
+func Test_writeAllContext(t *testing.T) {
+	type args struct {
+		ctx       context.Context
+		data      []byte
+		chunkSize int
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantW   string
+		wantErr bool
+	}{
+		{name: " chunkSize2", args: args{ctx: context.Background(), data: []byte(""), chunkSize: 2}, wantW: "", wantErr: false},
+		{name: "1 chunkSize2", args: args{ctx: context.Background(), data: []byte("1"), chunkSize: 2}, wantW: "1", wantErr: false},
+		{name: "12 chunkSize2", args: args{ctx: context.Background(), data: []byte("12"), chunkSize: 2}, wantW: "12", wantErr: false},
+		{name: "123 chunkSize2", args: args{ctx: context.Background(), data: []byte("123"), chunkSize: 2}, wantW: "123", wantErr: false},
+		{name: "1234 chunkSize2", args: args{ctx: context.Background(), data: []byte("1234"), chunkSize: 2}, wantW: "1234", wantErr: false},
+		{name: "12345 chunkSize2", args: args{ctx: context.Background(), data: []byte("12345"), chunkSize: 2}, wantW: "12345", wantErr: false},
+
+		{name: " chunkSize3", args: args{ctx: context.Background(), data: []byte(""), chunkSize: 3}, wantW: "", wantErr: false},
+		{name: "1 chunkSize3", args: args{ctx: context.Background(), data: []byte("1"), chunkSize: 3}, wantW: "1", wantErr: false},
+		{name: "12 chunkSize3", args: args{ctx: context.Background(), data: []byte("12"), chunkSize: 3}, wantW: "12", wantErr: false},
+		{name: "123 chunkSize3", args: args{ctx: context.Background(), data: []byte("123"), chunkSize: 3}, wantW: "123", wantErr: false},
+		{name: "1234 chunkSize3", args: args{ctx: context.Background(), data: []byte("1234"), chunkSize: 3}, wantW: "1234", wantErr: false},
+		{name: "12345 chunkSize3", args: args{ctx: context.Background(), data: []byte("12345"), chunkSize: 3}, wantW: "12345", wantErr: false},
+
+		{name: "12345 chunkSize2 error", args: args{ctx: &failContext{errAfter: 1, err: errors.New("contextError")}, data: []byte("12345"), chunkSize: 2}, wantW: "12", wantErr: true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			w := &bytes.Buffer{}
+			if err := writeAllContext(tt.args.ctx, w, tt.args.data, tt.args.chunkSize); (err != nil) != tt.wantErr {
+				t.Errorf("writeAllContext() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if gotW := w.String(); gotW != tt.wantW {
+				t.Errorf("writeAllContext() = %v, want %v", gotW, tt.wantW)
+			}
+		})
+	}
+}