Add unit test for rangeReader

handler/file/range_reader_test.go

@@ -0,0 +1,63 @@
+package file
+
+import (
+	"bytes"
+	"io"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+type testReadCloser struct {
+	*bytes.Reader
+	closed bool
+}
+
+func (rc *testReadCloser) Close() error {
+	rc.closed = true
+	return nil
+}
+
+func TestRangeReader(t *testing.T) {
+	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	var seededRand *rand.Rand = rand.New(rand.NewSource(time.Now().UnixNano()))
+	testData := make([]byte, 257)
+	for i := range testData {
+		testData[i] = charset[seededRand.Intn(len(charset))]
+	}
+
+	rc := &testReadCloser{
+		Reader: bytes.NewReader(testData),
+	}
+	rr := rangeReader{
+		reader:    rc,
+		remaining: rc.Size(),
+	}
+
+	outBuf := new(bytes.Buffer)
+
+	var totalRead int64
+	const readLen = 23
+	for {
+		n, err := rr.writeToN(outBuf, readLen)
+		totalRead += n
+		require.Equal(t, rc.Size()-totalRead, rr.remaining)
+		if n < readLen {
+			break
+		}
+		require.NoError(t, err)
+	}
+	require.Zero(t, rr.remaining)
+	require.Equal(t, rc.Size(), totalRead)
+	require.Equal(t, testData, outBuf.Bytes())
+
+	n, err := rr.writeToN(outBuf, readLen)
+	require.ErrorIs(t, err, io.EOF)
+	require.Zero(t, n)
+
+	require.NoError(t, rr.close())
+	require.True(t, rc.closed)
+	require.Nil(t, rr.reader)
+}