mw/autopath: integration test with erratic (#930)

Add integration test with erratic. For this erratic now also returns an
autopath searchpath. This tests the whole chain; i.e registring a
searchfunction and calling that from autopath.

This tests does a autopathing domain and a non-autopathing one.

test/erratic_autopath_test.go

@@ -0,0 +1,85 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+func TestLookupAutoPathErratic(t *testing.T) {
+	corefile := `.:0 {
+	erratic
+	autopath @erratic
+	proxy . 8.8.8.8:53
+	debug
+    }
+`
+	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()
+
+	tests := []struct {
+		qname          string
+		expectedAnswer string
+		expectedType   uint16
+	}{
+		{"google.com.a.example.org.", "google.com.a.example.org.", dns.TypeCNAME},
+		{"google.com.", "google.com.", dns.TypeA},
+	}
+
+	for i, tc := range tests {
+		m := new(dns.Msg)
+		// erratic always returns this search path: "a.example.org.", "b.example.org.", "".
+		m.SetQuestion(tc.qname, dns.TypeA)
+
+		r, err := dns.Exchange(m, udp)
+		if err != nil {
+			t.Fatalf("Test %d, failed to sent query: %q", i, err)
+		}
+		if len(r.Answer) == 0 {
+			t.Fatalf("Test %d, answer section should have RRs", i)
+		}
+		if x := r.Answer[0].Header().Name; x != tc.expectedAnswer {
+			t.Fatalf("Test %d, expected answer %s, got %s", i, tc.expectedAnswer, x)
+		}
+		if x := r.Answer[0].Header().Rrtype; x != tc.expectedType {
+			t.Fatalf("Test %d, expected answer type %d, got %d", i, tc.expectedType, x)
+		}
+	}
+}
+
+func TestAutoPathErraticNotLoaded(t *testing.T) {
+	corefile := `.:0 {
+	autopath @erratic
+	proxy . 8.8.8.8:53
+	debug
+    }
+`
+	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()
+
+	m := new(dns.Msg)
+	m.SetQuestion("google.com.a.example.org.", dns.TypeA)
+	r, err := dns.Exchange(m, udp)
+	if err != nil {
+		t.Fatalf("Failed to sent query: %q", err)
+	}
+	if r.Rcode != dns.RcodeNameError {
+		t.Fatalf("Expected NXDOMAIN, got %d", r.Rcode)
+	}
+}