mw/kubernetes: move fallthrough tests out (#1008)

* mw/kubernetes: move fallthrough tests out

Remove the testcase duplication and put fallthrough tests in separate
file.

Also make some names shorter and more descriptive.

* fix test build

* fix corefile

test/kubernetes_fallthrough_test.go

+// +build k8s
+
+package test
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"testing"
+
+	"github.com/coredns/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+)
+
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
+var dnsTestCasesFallthrough = []test.Case{
+	{
+		Qname: "ext-svc.test-1.svc.cluster.local.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeSuccess,
+		Answer: []dns.RR{
+			test.A("example.net.		303	IN	A	13.14.15.16"),
+			test.CNAME("ext-svc.test-1.svc.cluster.local. 303 IN	CNAME	example.net."),
+		},
+	},
+	{
+		Qname: "f.b.svc.cluster.local.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeSuccess,
+		Answer: []dns.RR{
+			test.A("f.b.svc.cluster.local.      303    IN      A       10.10.10.11"),
+		},
+		Ns: []dns.RR{
+			test.NS("cluster.local.	303	IN	NS	a.iana-servers.net."),
+			test.NS("cluster.local.	303	IN	NS	b.iana-servers.net."),
+		},
+	},
+	{
+		Qname: "foo.cluster.local.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeSuccess,
+		Answer: []dns.RR{
+			test.A("foo.cluster.local.      303    IN      A       10.10.10.10"),
+		},
+		Ns: []dns.RR{
+			test.NS("cluster.local.	303	IN	NS	a.iana-servers.net."),
+			test.NS("cluster.local.	303	IN	NS	b.iana-servers.net."),
+		},
+	},
+}
+
+func TestKubernetesFallthrough(t *testing.T) {
+	dbfile, rmFunc, err := TempFile(os.TempDir(), clusterLocal)
+	if err != nil {
+		t.Fatalf("Could not create zonefile for fallthrough server: %s", err)
+	}
+	defer rmFunc()
+
+	rmFunc, upstream, udp := upstreamServer(t)
+	defer upstream.Stop()
+	defer rmFunc()
+
+	corefile :=
+		`.:0 {
+    file ` + dbfile + ` cluster.local
+    kubernetes cluster.local {
+                endpoint http://localhost:8080
+		namespaces test-1
+		upstream ` + udp + `
+		fallthrough
+    }
+`
+	doIntegrationTests(t, corefile, dnsTestCasesFallthrough)
+}