diff --git a/sd/eureka/instancer.go b/sd/eureka/instancer.go
index 69c4556..d00b98c 100644
--- a/sd/eureka/instancer.go
+++ b/sd/eureka/instancer.go
@@ -33,15 +33,10 @@
 		quitc:  make(chan chan struct{}),
 	}
 
-	instances, err := s.getInstances()
-	if err == nil {
-		s.logger.Log("instances", len(instances))
-	} else {
-		s.logger.Log("during", "getInstances", "err", err)
-	}
-
-	s.cache.Update(sd.Event{Instances: instances, Err: err})
-	go s.loop()
+	done := make(chan struct{})
+	updates := conn.ScheduleAppUpdates(app, true, done)
+	s.consume(<-updates)
+	go s.loop(updates, done)
 	return s
 }
 
@@ -53,26 +48,24 @@
 	s.quitc = nil
 }
 
-func (s *Instancer) loop() {
-	var (
-		await   = false
-		done    = make(chan struct{})
-		updatec = s.conn.ScheduleAppUpdates(s.app, await, done)
-	)
+func (s *Instancer) consume(update fargo.AppUpdate) {
+	if update.Err != nil {
+		s.logger.Log("during", "Update", "err", update.Err)
+		s.cache.Update(sd.Event{Err: update.Err})
+		return
+	}
+	instances := convertFargoAppToInstances(update.App)
+	s.logger.Log("instances", len(instances))
+	s.cache.Update(sd.Event{Instances: instances})
+}
+
+func (s *Instancer) loop(updates <-chan fargo.AppUpdate, done chan<- struct{}) {
 	defer close(done)
 
 	for {
 		select {
-		case update := <-updatec:
-			if update.Err != nil {
-				s.logger.Log("during", "Update", "err", update.Err)
-				s.cache.Update(sd.Event{Err: update.Err})
-				continue
-			}
-			instances := convertFargoAppToInstances(update.App)
-			s.logger.Log("instances", len(instances))
-			s.cache.Update(sd.Event{Instances: instances})
-
+		case update := <-updates:
+			s.consume(update)
 		case q := <-s.quitc:
 			close(q)
 			return
diff --git a/sd/eureka/instancer_test.go b/sd/eureka/instancer_test.go
index 98c83e5..cde4c61 100644
--- a/sd/eureka/instancer_test.go
+++ b/sd/eureka/instancer_test.go
@@ -13,59 +13,75 @@
 
 func TestInstancer(t *testing.T) {
 	connection := &testConnection{
-		instances:      []*fargo.Instance{instanceTest1},
-		application:    appUpdateTest,
+		instances:      []*fargo.Instance{instanceTest1, instanceTest2},
 		errApplication: nil,
 	}
 
 	instancer := NewInstancer(connection, appNameTest, loggerTest)
 	defer instancer.Stop()
 
-	state := instancer.cache.State()
+	state := instancer.state()
 	if state.Err != nil {
 		t.Fatal(state.Err)
 	}
 
-	if want, have := 1, len(state.Instances); want != have {
+	if want, have := 2, len(state.Instances); want != have {
 		t.Errorf("want %d, have %d", want, have)
 	}
 }
 
-func TestInstancerScheduleUpdates(t *testing.T) {
+func TestInstancerReceivesUpdates(t *testing.T) {
 	connection := &testConnection{
 		instances:      []*fargo.Instance{instanceTest1},
-		application:    appUpdateTest,
 		errApplication: nil,
 	}
 
 	instancer := NewInstancer(connection, appNameTest, loggerTest)
 	defer instancer.Stop()
 
-	state := instancer.cache.State()
-	if want, have := 1, len(state.Instances); want != have {
-		t.Errorf("want %d, have %d", want, have)
+	verifyCount := func(want int) (have int, converged bool) {
+		const maxPollAttempts = 5
+		const delayPerAttempt = 200 * time.Millisecond
+		for i := 1; ; i++ {
+			state := instancer.state()
+			if have := len(state.Instances); want == have {
+				return have, true
+			} else if i == maxPollAttempts {
+				return have, false
+			}
+			time.Sleep(delayPerAttempt)
+		}
 	}
 
-	time.Sleep(50 * time.Millisecond)
+	if have, converged := verifyCount(1); !converged {
+		t.Fatalf("initial: want %d, have %d", 1, have)
+	}
 
-	state = instancer.cache.State()
-	if want, have := 2, len(state.Instances); want != have {
-		t.Errorf("want %v, have %v", want, have)
+	if err := connection.RegisterInstance(instanceTest2); err != nil {
+		t.Fatalf("failed to register an instance: %v", err)
+	}
+	if have, converged := verifyCount(2); !converged {
+		t.Fatalf("after registration: want %d, have %d", 2, have)
+	}
+
+	if err := connection.DeregisterInstance(instanceTest1); err != nil {
+		t.Fatalf("failed to unregister an instance: %v", err)
+	}
+	if have, converged := verifyCount(1); !converged {
+		t.Fatalf("after deregistration: want %d, have %d", 1, have)
 	}
 }
 
-func TestBadInstancerInstances(t *testing.T) {
+func TestBadInstancerScheduleUpdates(t *testing.T) {
 	connection := &testConnection{
-		instances:      []*fargo.Instance{},
-		errInstances:   errTest,
-		application:    appUpdateTest,
-		errApplication: nil,
+		instances:      []*fargo.Instance{instanceTest1},
+		errApplication: errTest,
 	}
 
 	instancer := NewInstancer(connection, appNameTest, loggerTest)
 	defer instancer.Stop()
 
-	state := instancer.cache.State()
+	state := instancer.state()
 	if state.Err == nil {
 		t.Fatal("expecting error")
 	}
@@ -74,33 +90,3 @@
 		t.Errorf("want %d, have %d", want, have)
 	}
 }
-
-func TestBadInstancerScheduleUpdates(t *testing.T) {
-	connection := &testConnection{
-		instances:      []*fargo.Instance{instanceTest1},
-		application:    appUpdateTest,
-		errApplication: errTest,
-	}
-
-	instancer := NewInstancer(connection, appNameTest, loggerTest)
-	defer instancer.Stop()
-
-	state := instancer.cache.State()
-	if state.Err != nil {
-		t.Error(state.Err)
-	}
-	if want, have := 1, len(state.Instances); want != have {
-		t.Errorf("want %d, have %d", want, have)
-	}
-
-	time.Sleep(50 * time.Millisecond)
-
-	state = instancer.cache.State()
-	if state.Err == nil {
-		t.Fatal("expecting error")
-	}
-
-	if want, have := 0, len(state.Instances); want != have {
-		t.Errorf("want %v, have %v", want, have)
-	}
-}
diff --git a/sd/eureka/registrar.go b/sd/eureka/registrar.go
index 99fef7c..7af7836 100644
--- a/sd/eureka/registrar.go
+++ b/sd/eureka/registrar.go
@@ -28,6 +28,10 @@
 type fargoUnsuccessfulHTTPResponse struct {
 	statusCode    int
 	messagePrefix string
+}
+
+func (u *fargoUnsuccessfulHTTPResponse) Error() string {
+	return fmt.Sprintf("err=%s code=%d", u.messagePrefix, u.statusCode)
 }
 
 // Registrar maintains service instance liveness information in Eureka.
@@ -110,18 +114,30 @@
 	}
 }
 
+func httpResponseStatusCode(err error) (code int, present bool) {
+	if code, ok := fargo.HTTPResponseStatusCode(err); ok {
+		return code, true
+	}
+	// Allow injection of errors for testing.
+	if u, ok := err.(*fargoUnsuccessfulHTTPResponse); ok {
+		return u.statusCode, true
+	}
+	return 0, false
+}
+
+func isNotFound(err error) bool {
+	code, ok := httpResponseStatusCode(err)
+	return ok && code == http.StatusNotFound
+}
+
 func (r *Registrar) heartbeat() error {
 	err := r.conn.HeartBeatInstance(r.instance)
-	if err != nil {
-		if u, ok := err.(*fargoUnsuccessfulHTTPResponse); ok && u.statusCode == http.StatusNotFound {
-			// Instance expired (e.g. network partition). Re-register.
-			r.logger.Log("during", "heartbeat", err.Error())
-			return r.conn.ReregisterInstance(r.instance)
-		}
+	if err == nil {
+		return nil
+	}
+	if isNotFound(err) {
+		// Instance expired (e.g. network partition). Re-register.
+		return r.conn.ReregisterInstance(r.instance)
 	}
 	return err
 }
-
-func (u *fargoUnsuccessfulHTTPResponse) Error() string {
-	return fmt.Sprintf("err=%s code=%d", u.messagePrefix, u.statusCode)
-}
diff --git a/sd/eureka/util_test.go b/sd/eureka/util_test.go
index a66e712..e8a71a4 100644
--- a/sd/eureka/util_test.go
+++ b/sd/eureka/util_test.go
@@ -2,16 +2,19 @@
 
 import (
 	"errors"
+	"fmt"
 	"reflect"
+	"sync"
+	"time"
 
 	"github.com/go-kit/kit/log"
 	"github.com/hudl/fargo"
 )
 
 type testConnection struct {
-	instances      []*fargo.Instance
-	application    *fargo.Application
-	errInstances   error
+	mu        sync.RWMutex
+	instances []*fargo.Instance
+
 	errApplication error
 	errHeartbeat   error
 	errRegister    error
@@ -23,10 +26,6 @@
 	errNotFound   = &fargoUnsuccessfulHTTPResponse{statusCode: 404, messagePrefix: "not found"}
 	loggerTest    = log.NewNopLogger()
 	appNameTest   = "go-kit"
-	appUpdateTest = &fargo.Application{
-		Name:      appNameTest,
-		Instances: []*fargo.Instance{instanceTest1, instanceTest2},
-	}
 	instanceTest1 = &fargo.Instance{
 		HostName:         "serveregistrar1.acme.org",
 		Port:             8080,
@@ -59,16 +58,18 @@
 var _ fargoConnection = (*testConnection)(nil)
 
 func (c *testConnection) RegisterInstance(i *fargo.Instance) error {
-	if c.errRegister == nil {
-		for _, instance := range c.instances {
-			if reflect.DeepEqual(*instance, *i) {
-				return errors.New("already registered")
-			}
+	if c.errRegister != nil {
+		return c.errRegister
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for _, instance := range c.instances {
+		if reflect.DeepEqual(*instance, *i) {
+			return errors.New("already registered")
 		}
-
-		c.instances = append(c.instances, i)
 	}
-	return c.errRegister
+	c.instances = append(c.instances, i)
+	return nil
 }
 
 func (c *testConnection) HeartBeatInstance(i *fargo.Instance) error {
@@ -76,33 +77,76 @@
 }
 
 func (c *testConnection) DeregisterInstance(i *fargo.Instance) error {
-	if c.errDeregister == nil {
-		var newInstances []*fargo.Instance
-		for _, instance := range c.instances {
-			if reflect.DeepEqual(*instance, *i) {
-				continue
-			}
-			newInstances = append(newInstances, instance)
+	if c.errDeregister != nil {
+		return c.errDeregister
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	remaining := make([]*fargo.Instance, 0, len(c.instances))
+	for _, instance := range c.instances {
+		if reflect.DeepEqual(*instance, *i) {
+			continue
 		}
-		if len(newInstances) == len(c.instances) {
-			return errors.New("not registered")
-		}
-
-		c.instances = newInstances
+		remaining = append(remaining, instance)
 	}
-	return c.errDeregister
+	if len(remaining) == len(c.instances) {
+		return errors.New("not registered")
+	}
+	c.instances = remaining
+	return nil
 }
 
 func (c *testConnection) ReregisterInstance(ins *fargo.Instance) error {
 	return nil
 }
 
-func (c *testConnection) ScheduleAppUpdates(name string, await bool, done <-chan struct{}) <-chan fargo.AppUpdate {
-	updatec := make(chan fargo.AppUpdate, 1)
-	updatec <- fargo.AppUpdate{App: c.application, Err: c.errApplication}
-	return updatec
+func (c *testConnection) instancesForApplication(name string) []*fargo.Instance {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	instances := make([]*fargo.Instance, 0, len(c.instances))
+	for _, i := range c.instances {
+		if i.App == name {
+			instances = append(instances, i)
+		}
+	}
+	return instances
 }
 
 func (c *testConnection) GetApp(name string) (*fargo.Application, error) {
-	return &fargo.Application{Name: appNameTest, Instances: c.instances}, c.errInstances
+	if err := c.errApplication; err != nil {
+		return nil, err
+	}
+	instances := c.instancesForApplication(name)
+	if len(instances) == 0 {
+		return nil, fmt.Errorf("Application not found for name=%s", name)
+	}
+	return &fargo.Application{Name: name, Instances: instances}, nil
 }
+
+func (c *testConnection) ScheduleAppUpdates(name string, await bool, done <-chan struct{}) <-chan fargo.AppUpdate {
+	updatec := make(chan fargo.AppUpdate, 1)
+	send := func() {
+		app, err := c.GetApp(name)
+		select {
+		case updatec <- fargo.AppUpdate{App: app, Err: err}:
+		default:
+		}
+	}
+
+	if await {
+		send()
+	}
+	go func() {
+		ticker := time.NewTicker(100 * time.Millisecond)
+		for {
+			select {
+			case <-ticker.C:
+				send()
+			case <-done:
+				ticker.Stop()
+				return
+			}
+		}
+	}()
+	return updatec
+}