connection_test.go | 45 +++++++++++++++++++++++++++++++++++++++++++++

diff --git a/connection_test.go b/connection_test.go
index 22b76f01c2ecd38ea6733837cc47d7a6c8ec1128..55181a9ca609bf2402f71ad405d00db109f7c1a1 100644
--- a/connection_test.go
+++ b/connection_test.go
@@ -4,6 +4,10 @@ import (
 	"testing"
 	"time"
 
+	"github.com/bradfitz/iter"
+
+	"bitbucket.org/anacrolix/go.torrent/internal/pieceordering"
+
 	"bitbucket.org/anacrolix/go.torrent/peer_protocol"
 )
 
@@ -48,3 +52,44 @@ 			t.Fatal("got unexpected non-keepalive")
 		}
 	}
 }
+
+func testRequestOrder(expected []int, ro *pieceordering.Instance, t *testing.T) {
+	e := ro.First()
+	for _, i := range expected {
+		if i != e.Piece() {
+			t.FailNow()
+		}
+		e = e.Next()
+	}
+	if e != nil {
+		t.FailNow()
+	}
+}
+
+// Tests the request ordering based on a connections priorities.
+func TestPieceRequestOrder(t *testing.T) {
+	c := connection{
+		pieceRequestOrder: pieceordering.New(),
+		piecePriorities:   []int{1, 4, 0, 3, 2},
+	}
+	testRequestOrder(nil, c.pieceRequestOrder, t)
+	c.pendPiece(2, piecePriorityNone)
+	testRequestOrder(nil, c.pieceRequestOrder, t)
+	c.pendPiece(1, piecePriorityNormal)
+	c.pendPiece(2, piecePriorityNormal)
+	testRequestOrder([]int{2, 1}, c.pieceRequestOrder, t)
+	c.pendPiece(0, piecePriorityNormal)
+	testRequestOrder([]int{2, 0, 1}, c.pieceRequestOrder, t)
+	c.pendPiece(1, piecePriorityReadahead)
+	testRequestOrder([]int{1, 2, 0}, c.pieceRequestOrder, t)
+	c.pendPiece(4, piecePriorityNow)
+	testRequestOrder([]int{4, 1, 2, 0}, c.pieceRequestOrder, t)
+	c.pendPiece(2, piecePriorityReadahead)
+	// N(4), R(1, 2), N(0)
+	testRequestOrder([]int{4, 1, 2, 0}, c.pieceRequestOrder, t)
+	// Note this intentially sets to None a piece that's not in the order.
+	for i := range iter.N(5) {
+		c.pendPiece(i, piecePriorityNone)
+	}
+	testRequestOrder(nil, c.pieceRequestOrder, t)
+}