Improve testability of new code

src/network.cpp

@@ -209,29 +209,31 @@ namespace net {
 
   /**
    * @brief Returns a string for use as the instance name for mDNS.
+   * @param hostname The hostname to use for instance name generation.
    * @return Hostname-based instance name or "Sunshine" if hostname is invalid.
    */
   std::string
-  mdns_instance_name() {
-    std::string hostname = boost::asio::ip::host_name();
+  mdns_instance_name(const std::string_view &hostname) {
+    // Start with the unmodified hostname
+    std::string instancename { hostname.data(), hostname.size() };
 
     // Truncate to 63 characters per RFC 6763 section 7.2.
-    if (hostname.size() > 63) {
-      hostname.resize(63);
+    if (instancename.size() > 63) {
+      instancename.resize(63);
     }
 
-    for (auto i = 0; i < hostname.size(); i++) {
+    for (auto i = 0; i < instancename.size(); i++) {
       // Replace any spaces with dashes
-      if (hostname[i] == ' ') {
-        hostname[i] = '-';
+      if (instancename[i] == ' ') {
+        instancename[i] = '-';
       }
-      else if (!std::isalnum(hostname[i]) && hostname[i] != '-') {
+      else if (!std::isalnum(instancename[i]) && instancename[i] != '-') {
         // Stop at the first invalid character
-        hostname.resize(i);
+        instancename.resize(i);
         break;
       }
     }
 
-    return !hostname.empty() ? hostname : "Sunshine";
+    return !instancename.empty() ? instancename : "Sunshine";
   }
 }  // namespace net

src/network.h

@@ -108,8 +108,9 @@ namespace net {
 
   /**
    * @brief Returns a string for use as the instance name for mDNS.
+   * @param hostname The hostname to use for instance name generation.
    * @return Hostname-based instance name or "Sunshine" if hostname is invalid.
    */
   std::string
-  mdns_instance_name();
+  mdns_instance_name(const std::string_view &hostname);
 }  // namespace net

src/platform/linux/publish.cpp

@@ -426,7 +426,7 @@ namespace platf::publish {
       return nullptr;
     }
 
-    auto instance_name = net::mdns_instance_name();
+    auto instance_name = net::mdns_instance_name(boost::asio::ip::host_name());
     name.reset(avahi::strdup(instance_name.c_str()));
 
     client.reset(

src/platform/windows/publish.cpp

@@ -107,9 +107,10 @@ namespace platf::publish {
     auto alarm = safe::make_alarm<PDNS_SERVICE_INSTANCE>();
 
     std::wstring domain { SERVICE_TYPE_DOMAIN.data(), SERVICE_TYPE_DOMAIN.size() };
-    std::wstring name = from_utf8(net::mdns_instance_name() + '.') + domain;
 
-    auto host = from_utf8(boost::asio::ip::host_name() + ".local");
+    auto hostname = boost::asio::ip::host_name();
+    auto name = from_utf8(net::mdns_instance_name(hostname) + '.') + domain;
+    auto host = from_utf8(hostname + ".local");
 
     DNS_SERVICE_INSTANCE instance {};
     instance.pszInstanceName = name.data();

tests/unit/test_network.cpp

@@ -6,18 +6,21 @@
 
 #include "../tests_common.h"
 
-TEST(MdnsInstanceNameTests, ValidLength) {
-  auto name = net::mdns_instance_name();
+struct MdnsInstanceNameTest: testing::TestWithParam<std::tuple<std::string, std::string>> {};
 
-  // The instance name must be 63 characters or less
-  EXPECT_LT(name.size(), 64);
+TEST_P(MdnsInstanceNameTest, Run) {
+  auto [input, expected] = GetParam();
+  ASSERT_EQ(net::mdns_instance_name(input), expected);
 }
 
-TEST(MdnsInstanceNameTests, ValidCharacters) {
-  auto name = net::mdns_instance_name();
-
-  // The string must not contain invalid hostname characters
-  for (const char& c : name) {
-    EXPECT_TRUE(std::isalnum(c) || c == '-');
-  }
-}
+INSTANTIATE_TEST_SUITE_P(
+  MdnsInstanceNameTests,
+  MdnsInstanceNameTest,
+  testing::Values(
+    std::make_tuple("shortname-123", "shortname-123"),
+    std::make_tuple("space 123", "space-123"),
+    std::make_tuple("hostname.domain.test", "hostname"),
+    std::make_tuple("&", "Sunshine"),
+    std::make_tuple("", "Sunshine"),
+    std::make_tuple("😁", "Sunshine"),
+    std::make_tuple(std::string(128, 'a'), std::string(63, 'a'))));