middleware/file: add test for reload (#361)

This add a highlevel integration test for zone reloading. It also
fixes a data race in the actual reloading process.

test/file_reload_test.go

@@ -0,0 +1,75 @@
+package test
+
+import (
+	"io/ioutil"
+	"log"
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/test"
+	"github.com/miekg/coredns/request"
+	"github.com/miekg/dns"
+)
+
+func TestZoneReload(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	name, rm, err := TempFile(".", exampleOrg)
+	if err != nil {
+		t.Fatalf("Failed to created zone: %s", err)
+	}
+	defer rm()
+
+	// Corefile with two stanzas
+	corefile := `example.org:0 {
+       file ` + name + `
+}
+
+example.net:0 {
+	file ` + name + `
+}
+`
+	i, err := CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	udp, _ := CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+	defer i.Stop()
+
+	p := proxy.New([]string{udp})
+	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
+
+	resp, err := p.Lookup(state, "example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+	if len(resp.Answer) != 2 {
+		t.Fatal("Expected two RR in answer section got %d", len(resp.Answer))
+	}
+
+	// Remove RR from the Apex
+	ioutil.WriteFile(name, []byte(exampleOrgUpdated), 0644)
+
+	time.Sleep(1 * time.Second) // fsnotify
+
+	resp, err = p.Lookup(state, "example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+
+	if len(resp.Answer) != 1 {
+		t.Fatal("Expected two RR in answer section got %d", len(resp.Answer))
+	}
+}
+
+const exampleOrgUpdated = `; example.org test file
+example.org.		IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082541 7200 3600 1209600 3600
+example.org.		IN	NS	b.iana-servers.net.
+example.org.		IN	NS	a.iana-servers.net.
+example.org.		IN	A	127.0.0.2
+`