Harden scan robustness and tests

common/dns_cache_test.go

@@ -0,0 +1,23 @@
+package common
+
+import "testing"
+
+func TestDNSCacheResolveIPAndCacheHit(t *testing.T) {
+	cache := &dnsCache{}
+
+	first, err := cache.ResolveIP("127.0.0.1")
+	if err != nil {
+		t.Fatalf("ResolveIP loopback error = %v", err)
+	}
+	second, err := cache.ResolveIP("127.0.0.1")
+	if err != nil {
+		t.Fatalf("ResolveIP cached loopback error = %v", err)
+	}
+	if first != second {
+		t.Fatal("ResolveIP should return cached address on second lookup")
+	}
+
+	if _, err := cache.ResolveIP("bad host with spaces"); err == nil {
+		t.Fatal("ResolveIP should reject an invalid host")
+	}
+}