general: adding the Clock interface to aid testing

This commit adds Clock and DefaultClock and moves the private
invoices.testClock under the clock package while adding basic
unit tests for it.
Clock is an interface currently encapsulating Now() and TickAfter().
It can be added as an external dependency to any class. This way
tests can stub out time.Now() or time.After().

The DefaultClock class simply returns the real time.Now() and
time.After().

clock/default_clock.go

@@ -0,0 +1,24 @@
+package clock
+
+import (
+	"time"
+)
+
+// DefaultClock implements Clock interface by simply calling the appropriate
+// time functions.
+type DefaultClock struct{}
+
+// NewDefaultClock constructs a new DefaultClock.
+func NewDefaultClock() Clock {
+	return &DefaultClock{}
+}
+
+// Now simply returns time.Now().
+func (DefaultClock) Now() time.Time {
+	return time.Now()
+}
+
+// TickAfter simply wraps time.After().
+func (DefaultClock) TickAfter(duration time.Duration) <-chan time.Time {
+	return time.After(duration)
+}

clock/interface.go

@@ -0,0 +1,16 @@
+package clock
+
+import (
+	"time"
+)
+
+// Clock is an interface that provides a time functions for LND packages.
+// This is useful during testing when a concrete time reference is needed.
+type Clock interface {
+	// Now returns the current local time (as defined by the Clock).
+	Now() time.Time
+
+	// TickAfter returns a channel that will receive a tick after the specified
+	// duration has passed.
+	TickAfter(duration time.Duration) <-chan time.Time
+}

clock/test_clock.go

@@ -1,42 +1,40 @@
-package invoices
+package clock
 
 import (
 	"sync"
 	"time"
 )
 
-// testClock can be used in tests to mock time.
-type testClock struct {
+// TestClock can be used in tests to mock time.
+type TestClock struct {
 	currentTime time.Time
 	timeChanMap map[time.Time][]chan time.Time
 	timeLock    sync.Mutex
 }
 
-// newTestClock returns a new test clock.
-func newTestClock(startTime time.Time) *testClock {
-	return &testClock{
+// NewTestClock returns a new test clock.
+func NewTestClock(startTime time.Time) *TestClock {
+	return &TestClock{
 		currentTime: startTime,
 		timeChanMap: make(map[time.Time][]chan time.Time),
 	}
 }
 
-// now returns the current (test) time.
-func (c *testClock) now() time.Time {
+// Now returns the current (test) time.
+func (c *TestClock) Now() time.Time {
 	c.timeLock.Lock()
 	defer c.timeLock.Unlock()
 
 	return c.currentTime
 }
 
-// tickAfter returns a channel that will receive a tick at the specified time.
-func (c *testClock) tickAfter(duration time.Duration) <-chan time.Time {
+// TickAfter returns a channel that will receive a tick after the specified
+// duration has passed passed by the user set test time.
+func (c *TestClock) TickAfter(duration time.Duration) <-chan time.Time {
 	c.timeLock.Lock()
 	defer c.timeLock.Unlock()
 
 	triggerTime := c.currentTime.Add(duration)
-	log.Debugf("tickAfter called: duration=%v, trigger_time=%v",
-		duration, triggerTime)
-
 	ch := make(chan time.Time, 1)
 
 	// If already expired, tick immediately.
@@ -53,8 +51,8 @@ func (c *testClock) tickAfter(duration time.Duration) <-chan time.Time {
 	return ch
 }
 
-// setTime sets the (test) time and triggers tick channels when they expire.
-func (c *testClock) setTime(now time.Time) {
+// SetTime sets the (test) time and triggers tick channels when they expire.
+func (c *TestClock) SetTime(now time.Time) {
 	c.timeLock.Lock()
 	defer c.timeLock.Unlock()
 

clock/test_clock_test.go

@@ -0,0 +1,63 @@
+package clock
+
+import (
+	"testing"
+	"time"
+)
+
+var (
+	testTime = time.Date(2009, time.January, 3, 12, 0, 0, 0, time.UTC)
+)
+
+func TestNow(t *testing.T) {
+	c := NewTestClock(testTime)
+	now := c.Now()
+
+	if now != testTime {
+		t.Fatalf("expected: %v, got: %v", testTime, now)
+	}
+
+	now = now.Add(time.Hour)
+	c.SetTime(now)
+	if c.Now() != now {
+		t.Fatalf("epected: %v, got: %v", now, c.Now())
+	}
+}
+
+func TestTickAfter(t *testing.T) {
+	c := NewTestClock(testTime)
+
+	// Should be ticking immediately.
+	ticker0 := c.TickAfter(0)
+
+	// Both should be ticking after SetTime
+	ticker1 := c.TickAfter(time.Hour)
+	ticker2 := c.TickAfter(time.Hour)
+
+	// We don't expect this one to tick.
+	ticker3 := c.TickAfter(2 * time.Hour)
+
+	tickOrTimeOut := func(ticker <-chan time.Time, expectTick bool) {
+		tick := false
+		select {
+		case <-ticker:
+			tick = true
+		case <-time.After(time.Millisecond):
+		}
+
+		if tick != expectTick {
+			t.Fatalf("expected tick: %v, ticked: %v", expectTick, tick)
+		}
+	}
+
+	tickOrTimeOut(ticker0, true)
+	tickOrTimeOut(ticker1, false)
+	tickOrTimeOut(ticker2, false)
+	tickOrTimeOut(ticker3, false)
+
+	c.SetTime(c.Now().Add(time.Hour))
+
+	tickOrTimeOut(ticker1, true)
+	tickOrTimeOut(ticker2, true)
+	tickOrTimeOut(ticker3, false)
+}

invoices/invoiceregistry.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/queue"
@@ -62,12 +63,10 @@ type RegistryConfig struct {
 	// waiting for the other set members to arrive.
 	HtlcHoldDuration time.Duration
 
-	// Now returns the current time.
-	Now func() time.Time
-
-	// TickAfter returns a channel that is sent on after the specified
-	// duration as passed.
-	TickAfter func(duration time.Duration) <-chan time.Time
+	// Clock holds the clock implementation that is used to provide
+	// Now() and TickAfter() and is useful to stub out the clock functions
+	// during testing.
+	Clock clock.Clock
 }
 
 // htlcReleaseEvent describes an htlc auto-release event. It is used to release
@@ -177,8 +176,8 @@ type invoiceEvent struct {
 // tickAt returns a channel that ticks at the specified time. If the time has
 // already passed, it will tick immediately.
 func (i *InvoiceRegistry) tickAt(t time.Time) <-chan time.Time {
-	now := i.cfg.Now()
-	return i.cfg.TickAfter(t.Sub(now))
+	now := i.cfg.Clock.Now()
+	return i.cfg.Clock.TickAfter(t.Sub(now))
 }
 
 // invoiceEventLoop is the dedicated goroutine responsible for accepting

invoices/invoiceregistry_test.go

@@ -587,7 +587,7 @@ func TestSettleMpp(t *testing.T) {
 	}
 
 	// Simulate mpp timeout releasing htlc 1.
-	ctx.clock.setTime(testTime.Add(30 * time.Second))
+	ctx.clock.SetTime(testTime.Add(30 * time.Second))
 
 	hodlEvent := (<-hodlChan1).(HodlEvent)
 	if hodlEvent.Preimage != nil {

invoices/test_utils_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
@@ -120,27 +121,26 @@ func newTestChannelDB() (*channeldb.DB, func(), error) {
 
 type testContext struct {
 	registry *InvoiceRegistry
-	clock    *testClock
+	clock    *clock.TestClock
 
 	cleanup func()
 	t       *testing.T
 }
 
 func newTestContext(t *testing.T) *testContext {
-	clock := newTestClock(testTime)
+	clock := clock.NewTestClock(testTime)
 
 	cdb, cleanup, err := newTestChannelDB()
 	if err != nil {
 		t.Fatal(err)
 	}
-	cdb.Now = clock.now
+	cdb.Now = clock.Now
 
 	// Instantiate and start the invoice ctx.registry.
 	cfg := RegistryConfig{
 		FinalCltvRejectDelta: testFinalCltvRejectDelta,
 		HtlcHoldDuration:     30 * time.Second,
-		Now:                  clock.now,
-		TickAfter:            clock.tickAfter,
+		Clock:                clock,
 	}
 	registry := NewRegistry(cdb, &cfg)
 

server.go

@@ -33,6 +33,7 @@ import (
 	"github.com/lightningnetwork/lnd/chanfitness"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channelnotifier"
+	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/contractcourt"
 	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/feature"
@@ -381,8 +382,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 	registryConfig := invoices.RegistryConfig{
 		FinalCltvRejectDelta: defaultFinalCltvRejectDelta,
 		HtlcHoldDuration:     invoices.DefaultHtlcHoldDuration,
-		Now:                  time.Now,
-		TickAfter:            time.After,
+		Clock:                clock.NewDefaultClock(),
 	}
 
 	s := &server{