av/stream/flac: added writeseeker tests

stream/flac/flac_test.go

@@ -27,6 +27,7 @@ LICENSE
 package flac
 
 import (
+	"io"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -37,6 +38,49 @@ const (
 	outFile  = "testOut.wav"
 )
 
+func TestWriteSeekerWrite(t *testing.T) {
+	writerSeeker := &writeSeeker{}
+	var ws io.WriteSeeker = writerSeeker
+
+	ws.Write([]byte("hello"))
+	if string(writerSeeker.buf) != "hello" {
+		t.Fail()
+	}
+
+	ws.Write([]byte(" world"))
+	if string(writerSeeker.buf) != "hello world" {
+		t.Fail()
+	}
+
+}
+
+func TestWriteSeekerSeek(t *testing.T) {
+	writerSeeker := &writeSeeker{}
+	var ws io.WriteSeeker = writerSeeker
+
+	ws.Write([]byte("hello"))
+	if string(writerSeeker.buf) != "hello" {
+		t.Fail()
+	}
+
+	ws.Write([]byte(" world"))
+	if string(writerSeeker.buf) != "hello world" {
+		t.Fail()
+	}
+
+	ws.Seek(-2, io.SeekEnd)
+	ws.Write([]byte("k!"))
+	if string(writerSeeker.buf) != "hello work!" {
+		t.Fail()
+	}
+
+	ws.Seek(6, io.SeekStart)
+	ws.Write([]byte("gopher"))
+	if string(writerSeeker.buf) != "hello gopher" {
+		t.Fail()
+	}
+}
+
 func TestDecodeFlac(t *testing.T) {
 	b, err := ioutil.ReadFile(testFile)
 	if err != nil {