htlcswitch: add new concurrentTester wrapper struct

In this commit we add a new wrapper struct for the testing.T struct
that allows multiple clients to attempt to fail a given test at the
same time.

htlcswitch/link_test.go

@@ -27,6 +27,27 @@ const (
 	testStartingHeight = 100
 )
 
+// concurrentTester is a thread-safe wrapper around the Fatalf method of a
+// *testing.T instance. With this wrapper multiple goroutines can safely
+// attempt to fail a test concurrently.
+type concurrentTester struct {
+	mtx sync.Mutex
+	*testing.T
+}
+
+func newConcurrentTester(t *testing.T) *concurrentTester {
+	return &concurrentTester{
+		T: t,
+	}
+}
+
+func (c *concurrentTester) Fatalf(format string, args ...interface{}) {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+
+	c.T.Fatalf(format, args)
+}
+
 // messageToString is used to produce less spammy log messages in trace mode by
 // setting the 'Curve" parameter to nil. Doing this avoids printing out each of
 // the field elements in the curve parameters for secp256k1.
@@ -1872,6 +1893,8 @@ func TestChannelRetransmission(t *testing.T) {
 
 		// Add interceptor to check the order of Bob and Alice messages.
 		n := newThreeHopNetwork(t,
+		ct := newConcurrentTester(t)
+
 			channels.aliceToBob, channels.bobToAlice,
 			channels.bobToCarol, channels.carolToBob,
 			testStartingHeight,

htlcswitch/mock.go

@@ -30,7 +30,7 @@ type mockServer struct {
 	wg       sync.WaitGroup
 	quit     chan struct{}
 
-	t *testing.T
+	t testing.TB
 
 	name     string
 	messages chan lnwire.Message
@@ -46,7 +46,7 @@ type mockServer struct {
 
 var _ Peer = (*mockServer)(nil)
 
-func newMockServer(t *testing.T, name string) *mockServer {
+func newMockServer(t testing.TB, name string) *mockServer {
 	var id [33]byte
 	h := sha256.Sum256([]byte(name))
 	copy(id[:], h[:])

htlcswitch/test_utils.go

@@ -608,7 +608,6 @@ func (n *threeHopNetwork) stop() {
 	}
 }
 
-// clusterChannels...
 type clusterChannels struct {
 	aliceToBob *lnwallet.LightningChannel
 	bobToAlice *lnwallet.LightningChannel
@@ -685,7 +684,7 @@ func createClusterChannels(aliceToBob, bobToCarol btcutil.Amount) (
 // alice                   first bob    second bob              carol
 // channel link	    	  channel link   channel link		channel link
 //
-func newThreeHopNetwork(t *testing.T, aliceChannel, firstBobChannel,
+func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 	secondBobChannel, carolChannel *lnwallet.LightningChannel,
 	startingHeight uint32) *threeHopNetwork {