add archive of single non-empty file

main.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"archive/zip"
+	"fmt"
+	"io"
 	"os"
 )
 
@@ -14,8 +16,9 @@ func NewArchiver(archive *os.File) *Archiver {
 	return &Archiver{Dest: archive, w: zip.NewWriter(archive)}
 }
 
-func (a *Archiver) Archive() {
-	a.w.Create("hello.txt")
+func (a *Archiver) Archive(r io.Reader) {
+	writer, _ := a.w.Create("hello.txt")
+	fmt.Fprint(writer, r)
 	a.w.Close()
 }
 

main_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"archive/zip"
+	"bytes"
 	"fmt"
 	"os"
 	"testing"
@@ -11,11 +12,12 @@ import (
 
 func TestArchive(t *testing.T) {
 	t.Run("archives a single empty file called hello.txt", func(t *testing.T) {
+		file := bytes.NewBufferString("")
 		archive, cleanup := createTempArchive(t, "testdata/archive.zip")
 		defer cleanup()
 
 		archiver := NewArchiver(archive)
-		archiver.Archive()
+		archiver.Archive(file)
 
 		archiveReader, err := zip.OpenReader(archive.Name())
 		assert.NoError(t, err)
@@ -24,6 +26,24 @@ func TestArchive(t *testing.T) {
 		assert.Equal(t, 1, len(archiveReader.File))
 		assert.Equal(t, "hello.txt", archiveReader.File[0].Name)
 	})
+
+	t.Run("archives a single non-empty file called hello.txt", func(t *testing.T) {
+		file := bytes.NewBufferString("hello, world!")
+		archive, cleanup := createTempArchive(t, "testdata/archive.zip")
+		defer cleanup()
+
+		archiver := NewArchiver(archive)
+		archiver.Archive(file)
+
+		archiveReader, err := zip.OpenReader(archive.Name())
+		assert.NoError(t, err)
+		defer archiveReader.Close()
+
+		got := archiveReader.File[0].UncompressedSize64
+		want := uint64(file.Len())
+
+		assert.Equal(t, want, got, "expected %s to have size %d but got %d", "hello.txt", want, got)
+	})
 }
 
 func createTempArchive(t testing.TB, name string) (*os.File, func()) {