test: add object reader test

feature/s3/manager/reader_test.go

@@ -0,0 +1,43 @@
+package manager_test
+
+import (
+	"context"
+	"io"
+	"reflect"
+	"testing"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/feature/s3/manager"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+)
+
+func TestObjectReader(t *testing.T) {
+	c, invocations, ranges := newDownloadRangeClient(buf12MB)
+
+	d := manager.NewDownloader(c, func(d *manager.Downloader) {
+		d.Concurrency = 1
+	})
+
+	rd := d.NewReader(context.Background(), &s3.GetObjectInput{
+		Bucket: aws.String("bucket"),
+		Key:    aws.String("key"),
+	})
+
+	n, err := io.Copy(io.Discard, rd)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	if e, a := int64(len(buf12MB)), n; e != a {
+		t.Errorf("expected %d buffer length, got %d", e, a)
+	}
+
+	if e, a := 4, *invocations; e != a {
+		t.Errorf("expect %v API calls, got %v", e, a)
+	}
+
+	expectRngs := []string{"bytes=0-0", "bytes=0-5242880", "bytes=5242881-10485761", "bytes=10485762-12582912"}
+	if e, a := expectRngs, *ranges; !reflect.DeepEqual(e, a) {
+		t.Errorf("expect %v ranges, got %v", e, a)
+	}
+}