diff --git a/gateway/handlers/function_cache_test.go b/gateway/handlers/function_cache_test.go
index 8d0cb064..edee342c 100644
--- a/gateway/handlers/function_cache_test.go
+++ b/gateway/handlers/function_cache_test.go
@@ -73,3 +73,43 @@ func Test_CacheGivesHitWithLongExpiry(t *testing.T) {
 		t.Errorf("hit, want: %v, got %v", wantHit, hit)
 	}
 }
+
+func Test_CacheFunctionExists(t *testing.T) {
+	fnName := "echo"
+
+	cache := FunctionCache{
+		Cache:  make(map[string]*FunctionMeta),
+		Expiry: time.Millisecond * 10,
+	}
+
+	cache.Set(fnName, ServiceQueryResponse{AvailableReplicas: 1})
+	time.Sleep(time.Millisecond * 2)
+
+	_, hit := cache.Get(fnName)
+
+	wantHit := true
+
+	if hit != wantHit {
+		t.Errorf("hit, want: %v, got %v", wantHit, hit)
+	}
+}
+func Test_CacheFunctionNotExist(t *testing.T) {
+	fnName := "echo"
+	testName := "burt"
+
+	cache := FunctionCache{
+		Cache:  make(map[string]*FunctionMeta),
+		Expiry: time.Millisecond * 10,
+	}
+
+	cache.Set(fnName, ServiceQueryResponse{AvailableReplicas: 1})
+	time.Sleep(time.Millisecond * 2)
+
+	_, hit := cache.Get(testName)
+
+	wantHit := false
+
+	if hit != wantHit {
+		t.Errorf("hit, want: %v, got %v", wantHit, hit)
+	}
+}
diff --git a/gateway/handlers/scaling.go b/gateway/handlers/scaling.go
index 5827078d..67f45ef1 100644
--- a/gateway/handlers/scaling.go
+++ b/gateway/handlers/scaling.go
@@ -36,7 +36,6 @@ func MakeScalingHandler(next http.HandlerFunc, upstream http.HandlerFunc, config
 		}
 
 		queryResponse, err := config.ServiceQuery.GetReplicas(functionName)
-		cache.Set(functionName, queryResponse)
 
 		if err != nil {
 			var errStr string
@@ -48,6 +47,8 @@ func MakeScalingHandler(next http.HandlerFunc, upstream http.HandlerFunc, config
 			return
 		}
 
+		cache.Set(functionName, queryResponse)
+
 		if queryResponse.AvailableReplicas == 0 {
 			minReplicas := uint64(1)
 			if queryResponse.MinReplicas > 0 {
diff --git a/gateway/plugin/external.go b/gateway/plugin/external.go
index 4a9bfd3f..b8fcd6ae 100644
--- a/gateway/plugin/external.go
+++ b/gateway/plugin/external.go
@@ -61,6 +61,7 @@ type ScaleServiceRequest struct {
 // GetReplicas replica count for function
 func (s ExternalServiceQuery) GetReplicas(serviceName string) (handlers.ServiceQueryResponse, error) {
 	var err error
+	var emptyServiceQueryResponse handlers.ServiceQueryResponse
 
 	function := requests.Function{}
 
@@ -88,6 +89,8 @@ func (s ExternalServiceQuery) GetReplicas(serviceName string) (handlers.ServiceQ
 			if err != nil {
 				log.Println(urlPath, err)
 			}
+		} else {
+			return emptyServiceQueryResponse, fmt.Errorf("server returned non-200 status code (%d) for function, %s", res.StatusCode, serviceName)
 		}
 	}
 
diff --git a/gateway/plugin/external_test.go b/gateway/plugin/external_test.go
index c2698ab3..1d14ab00 100644
--- a/gateway/plugin/external_test.go
+++ b/gateway/plugin/external_test.go
@@ -1,6 +1,15 @@
 package plugin
 
-import "testing"
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/openfaas/faas-provider/auth"
+	"github.com/openfaas/faas/gateway/handlers"
+)
 
 const fallbackValue = 120
 
@@ -30,3 +39,101 @@ func TestLabelValueWasInValid(t *testing.T) {
 		t.Fail()
 	}
 }
+func TestGetReplicasNonExistentFn(t *testing.T) {
+
+	testServer := httptest.NewServer(
+		http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+			res.WriteHeader(http.StatusNotFound)
+		}))
+	defer testServer.Close()
+
+	var creds auth.BasicAuthCredentials
+
+	url, _ := url.Parse(testServer.URL + "/")
+
+	esq := NewExternalServiceQuery(*url, &creds)
+
+	svcQryResp, err := esq.GetReplicas("burt")
+
+	if err == nil {
+		t.Logf("Error was nil, expected non-nil - the service query response value was %+v ", svcQryResp)
+		t.Fail()
+	}
+}
+
+func TestGetReplicasExistentFn(t *testing.T) {
+
+	testServer := httptest.NewServer(
+		http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+			res.WriteHeader(http.StatusOK)
+			res.Write([]byte(`{"json":"body"}`))
+		}))
+	defer testServer.Close()
+
+	expectedSvcQryResp := handlers.ServiceQueryResponse{
+		Replicas:          0,
+		MaxReplicas:       uint64(handlers.DefaultMaxReplicas),
+		MinReplicas:       uint64(handlers.DefaultMinReplicas),
+		ScalingFactor:     uint64(handlers.DefaultScalingFactor),
+		AvailableReplicas: 0,
+	}
+
+	var creds auth.BasicAuthCredentials
+
+	url, _ := url.Parse(testServer.URL + "/")
+
+	esq := NewExternalServiceQuery(*url, &creds)
+
+	svcQryResp, err := esq.GetReplicas("burt")
+
+	if err != nil {
+		t.Logf("Expected err to be nil got: %s ", err.Error())
+		t.Fail()
+	}
+	if svcQryResp != expectedSvcQryResp {
+		t.Logf("Unexpected return values - wanted %+v, got: %+v ", expectedSvcQryResp, svcQryResp)
+		t.Fail()
+	}
+}
+
+func TestSetReplicasNonExistentFn(t *testing.T) {
+
+	testServer := httptest.NewServer(
+		http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+			res.WriteHeader(http.StatusInternalServerError)
+		}))
+	defer testServer.Close()
+
+	var creds auth.BasicAuthCredentials
+	url, _ := url.Parse(testServer.URL + "/")
+	esq := NewExternalServiceQuery(*url, &creds)
+
+	err := esq.SetReplicas("burt", 1)
+
+	expectedErrStr := "error scaling HTTP code 500"
+
+	if !strings.Contains(err.Error(), expectedErrStr) {
+		t.Logf("Wanted string containing %s, got %s", expectedErrStr, err.Error())
+		t.Fail()
+	}
+}
+
+func TestSetReplicasExistentFn(t *testing.T) {
+
+	testServer := httptest.NewServer(
+		http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+			res.WriteHeader(http.StatusOK)
+		}))
+	defer testServer.Close()
+
+	var creds auth.BasicAuthCredentials
+	url, _ := url.Parse(testServer.URL + "/")
+	esq := NewExternalServiceQuery(*url, &creds)
+
+	err := esq.SetReplicas("burt", 1)
+
+	if err != nil {
+		t.Logf("Expected err to be nil got: %s ", err.Error())
+		t.Fail()
+	}
+}