test for read at pos

pkg/storage/local/read.go

@@ -13,6 +13,9 @@ func (l *LocalStorage) ReadFile(name string) ([]byte, error) {
 
 func (l *LocalStorage) OpenFilesFromPos(names []string, pos int64) ([]io.ReadCloser, error) {
 	readers := []io.ReadCloser{}
+	if pos < 0 {
+		return readers, nil
+	}
 	for _, name := range names {
 		file, err := os.Open(path.Join(l.path, name))
 		if err != nil {

pkg/storage/local/read_test.go

@@ -0,0 +1,91 @@
+package localstorage
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"path"
+	"testing"
+)
+
+func TestOpenFilesFromPos(t *testing.T) {
+	pwd, err := os.Executable()
+	if err != nil {
+		t.Fatalf("os Executable error: %s", err)
+	}
+	l := LocalStorage{
+		path: path.Dir(pwd),
+	}
+	contents1 := []byte(`this is the first file`)
+	contents2 := []byte(`this is the second file`)
+	err = l.WriteFile("1.txt", contents1)
+	if err != nil {
+		t.Fatalf("write file error: %s", err)
+	}
+	err = l.WriteFile("2.txt", contents2)
+	if err != nil {
+		t.Fatalf("write file error: %s", err)
+	}
+	t.Cleanup(func() {
+		err = os.Remove(path.Join(l.path, "1.txt"))
+		if err != nil {
+			t.Fatalf("file delete error: %s", err)
+		}
+		err = os.Remove(path.Join(l.path, "2.txt"))
+		if err != nil {
+			t.Fatalf("file delete error: %s", err)
+		}
+	})
+	expected := []string{
+		"this is the first filethis is the second file",
+		"is the first filethis is the second file",
+		"this is the second file",
+		"ethis is the second file",
+		"his is the second file",
+		"",
+		"",
+		"",
+	}
+	expextedOpenFiles := []int{
+		2,
+		2,
+		1,
+		2,
+		1,
+		0,
+		0,
+		0,
+	}
+	tests := []int64{
+		0,
+		5,
+		int64(len(contents1)),
+		int64(len(contents1) - 1),
+		int64(len(contents1) + 1),
+		int64(len(contents1) + len(contents2)),
+		int64(len(contents1) + len(contents2) + 1),
+		-5,
+	}
+	for k, pos := range tests {
+		files, err := l.OpenFilesFromPos([]string{"1.txt", "2.txt"}, pos)
+		if err != nil {
+			t.Fatalf("open file error: %s", err)
+		}
+		contents := bytes.NewBuffer([]byte{})
+		for _, file := range files {
+			defer file.Close()
+			body, err := io.ReadAll(file)
+			if err != nil {
+				t.Fatalf("could not read file: %s", err)
+			}
+			contents.Write(body)
+		}
+		if expected[k] != contents.String() {
+			t.Fatalf("unexpected output: expected '%s' got '%s'", expected[k], contents.String())
+		}
+		if expextedOpenFiles[k] != len(files) {
+			t.Fatalf("unexpected open files: expected %d got %d", expextedOpenFiles[k], len(files))
+		}
+	}
+
+}