Clarify native mocks and advert truncation tests

test/mocks/Arduino.h

@@ -6,6 +6,8 @@
 #include <string.h>
 #include <stdio.h>
 
+// Mock Arduino compatibility header for native testing.
+// Provides the small libc-backed helpers needed by Arduino-oriented code.
 inline char* ltoa(long value, char* buffer, int base) {
   if (base == 10) {
     snprintf(buffer, 32, "%ld", value);

test/mocks/Ed25519.h

@@ -10,6 +10,8 @@ extern "C" {
 
 #include <stdint.h>
 
+// Mock Ed25519 wrapper for native testing.
+// Adapts the test-only C ed25519 implementation to the Arduino-style class API.
 class Ed25519 {
 public:
   static bool verify(const uint8_t* sig, const uint8_t* pub_key, const uint8_t* message, int msg_len) {

test/mocks/SHA256.h

@@ -4,6 +4,8 @@
 #include <stddef.h>
 #include <string.h>
 
+// Mock SHA256 class for native testing.
+// Provides a deterministic stand-in so code can hash data without Arduino crypto deps.
 class SHA256 {
   uint32_t state_ = 2166136261u;
 

test/mocks/Stream.h

@@ -3,6 +3,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+// Mock Stream class for native testing.
+// Provides the minimal interface needed by code that depends on Arduino Stream.
 class Stream {
 public:
     virtual size_t readBytes(uint8_t*, size_t) { return 0; }

test/test_helpers/test_advert_data.cpp

@@ -329,6 +329,7 @@ TEST(AdvertData, ParsesPositiveLatitudeAndNegativeLongitudeBoundariesFromNetwork
   WriteI32Le(app_data, &offset, 90000000);
   // longitude field: minimum supported longitude, -180.000000 degrees.
   WriteI32Le(app_data, &offset, -180000000);
+  // name field: raw bytes for "dummy-node-name".
   WriteStringLiteral(app_data, &offset, "dummy-node-name");
 
   constexpr uint32_t current_timestamp = 1704067200U;
@@ -349,8 +350,11 @@ TEST(AdvertData, ParsesNullIslandCoordinatesFromNetworkPacket) {
 
   // flags/type byte: chat advert with zero-valued coordinates and a name.
   WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+  // latitude field: Null Island latitude at exactly 0.000000 degrees.
   WriteI32Le(app_data, &offset, 0);
+  // longitude field: Null Island longitude at exactly 0.000000 degrees.
   WriteI32Le(app_data, &offset, 0);
+  // name field: raw bytes for "dummy-node-name".
   WriteStringLiteral(app_data, &offset, "dummy-node-name");
 
   constexpr uint32_t current_timestamp = 1704067200U;
@@ -411,19 +415,15 @@ TEST(AdvertData, RejectsLongitudeBelowValidRangeFromNetworkPacket) {
   EXPECT_FALSE(test_mesh->discovered_contact.has_value());
 }
 
-void ExpectTruncatedGpsPayloadIsRejected(uint8_t app_data_len) {
-  uint8_t app_data[MAX_ADVERT_DATA_SIZE] = {};
+TEST(AdvertData, RejectsGpsPayloadWithMissingFlagsByte) {
+  // Backing storage is unused because the advertised app_data length is zero.
+  uint8_t app_data[1] = {};
   size_t offset = 0;
 
-  // Advert claims to carry GPS coordinates and a name, but the payload is truncated.
-  WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
-  WriteI32Le(app_data, &offset, 37774900);
-  WriteI32Le(app_data, &offset, -122419400);
-  WriteStringLiteral(app_data, &offset, "dummy-node-name");
-
   constexpr uint32_t current_timestamp = 1704067200U;
   constexpr uint32_t advert_timestamp = current_timestamp + 1;
-  mesh::Packet packet = BuildSignedAdvertPacket(advert_timestamp, app_data, app_data_len);
+  // Leave the app_data length at zero so the parser never sees the flags byte.
+  mesh::Packet packet = BuildSignedAdvertPacket(advert_timestamp, app_data, offset);
 
   auto test_mesh = MakeTestMesh(current_timestamp);
   test_mesh->recv(&packet);
@@ -431,20 +431,67 @@ void ExpectTruncatedGpsPayloadIsRejected(uint8_t app_data_len) {
   EXPECT_FALSE(test_mesh->discovered_contact.has_value());
 }
 
-TEST(AdvertData, RejectsGpsPayloadWithMissingFlagsByte) {
-  ExpectTruncatedGpsPayloadIsRejected(0);
-}
-
 TEST(AdvertData, RejectsGpsPayloadWithOnlyFlagsByte) {
-  ExpectTruncatedGpsPayloadIsRejected(1);
+  uint8_t app_data[1] = {};
+  size_t offset = 0;
+
+  // flags/type byte: chat advert that claims to carry coordinates and a name.
+  WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+
+  constexpr uint32_t current_timestamp = 1704067200U;
+  constexpr uint32_t advert_timestamp = current_timestamp + 1;
+  // Pass only the flags byte so no latitude bytes remain.
+  mesh::Packet packet = BuildSignedAdvertPacket(advert_timestamp, app_data, offset);
+
+  auto test_mesh = MakeTestMesh(current_timestamp);
+  test_mesh->recv(&packet);
+
+  EXPECT_FALSE(test_mesh->discovered_contact.has_value());
 }
 
 TEST(AdvertData, RejectsGpsPayloadWithLatitudeButMissingLongitude) {
-  ExpectTruncatedGpsPayloadIsRejected(5);
+  uint8_t app_data[5] = {};
+  size_t offset = 0;
+
+  // flags/type byte: chat advert that claims to carry coordinates and a name.
+  WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+  // latitude field: complete latitude bytes are present before truncation.
+  WriteI32Le(app_data, &offset, 37774900);
+
+  constexpr uint32_t current_timestamp = 1704067200U;
+  constexpr uint32_t advert_timestamp = current_timestamp + 1;
+  // Pass only the flags byte and latitude field so longitude is missing.
+  mesh::Packet packet = BuildSignedAdvertPacket(advert_timestamp, app_data, offset);
+
+  auto test_mesh = MakeTestMesh(current_timestamp);
+  test_mesh->recv(&packet);
+
+  EXPECT_FALSE(test_mesh->discovered_contact.has_value());
 }
 
 TEST(AdvertData, RejectsGpsPayloadOneByteShortOfFullCoordinates) {
-  ExpectTruncatedGpsPayloadIsRejected(8);
+  uint8_t app_data[8] = {};
+  size_t offset = 0;
+  uint8_t lon_bytes[sizeof(int32_t)] = {};
+  size_t lon_offset = 0;
+
+  // flags/type byte: chat advert that claims to carry coordinates and a name.
+  WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+  // latitude field: complete latitude bytes are present before truncation.
+  WriteI32Le(app_data, &offset, 37774900);
+  // longitude field: only the first three longitude bytes are present before truncation.
+  WriteI32Le(lon_bytes, &lon_offset, -122419400);
+  WriteBytes(app_data, &offset, lon_bytes, 3);
+
+  constexpr uint32_t current_timestamp = 1704067200U;
+  constexpr uint32_t advert_timestamp = current_timestamp + 1;
+  // Pass only the flags byte, latitude field, and three longitude bytes.
+  mesh::Packet packet = BuildSignedAdvertPacket(advert_timestamp, app_data, offset);
+
+  auto test_mesh = MakeTestMesh(current_timestamp);
+  test_mesh->recv(&packet);
+
+  EXPECT_FALSE(test_mesh->discovered_contact.has_value());
 }
 
 TEST(AdvertData, RejectsLatitudeOutsideValidRangeFromNetworkPacket) {
@@ -499,6 +546,7 @@ TEST(AdvertData, KeepsExistingGpsWhenUpdatedAdvertOmitsCoordinates) {
 
   // flags/type byte: chat advert with a new name but no GPS fields.
   WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_NAME_MASK);
+  // name field: replacement contact name with no coordinate payload following it.
   WriteStringLiteral(app_data, &offset, "updated-name");
 
   constexpr uint32_t current_timestamp = 1704067200U;
@@ -527,8 +575,11 @@ TEST(AdvertData, OverwritesExistingGpsWhenUpdatedAdvertIncludesCoordinates) {
 
   // flags/type byte: chat advert with replacement GPS coordinates and a new name.
   WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+  // latitude field: replacement latitude for 40.712800 degrees.
   WriteI32Le(app_data, &offset, 40712800);
+  // longitude field: replacement longitude for -74.006000 degrees.
   WriteI32Le(app_data, &offset, -74006000);
+  // name field: replacement contact name applied with the new coordinates.
   WriteStringLiteral(app_data, &offset, "updated-name");
 
   constexpr uint32_t current_timestamp = 1704067200U;
@@ -557,8 +608,11 @@ TEST(AdvertData, LeavesExistingGpsUntouchedWhenUpdatedAdvertHasInvalidCoordinate
 
   // flags/type byte: chat advert with invalid longitude and a new name.
   WriteU8(app_data, &offset, ADV_TYPE_CHAT | ADV_LATLON_MASK | ADV_NAME_MASK);
+  // latitude field: valid latitude so the update failure comes from longitude.
   WriteI32Le(app_data, &offset, 37774900);
+  // longitude field: one microdegree above +180.0, which should reject the update.
   WriteI32Le(app_data, &offset, 180000001);
+  // name field: replacement name that should not be applied when parsing fails.
   WriteStringLiteral(app_data, &offset, "updated-name");
 
   constexpr uint32_t current_timestamp = 1704067200U;