add unit test for mapping packets with lower sequence number than the…

… first mapped packet

see versatica#1437 and versatica#1438. Works but why not have a test

worker/test/src/RTC/TestSeqManager.cpp

@@ -1400,4 +1400,19 @@ SCENARIO("SeqManager", "[rtc][SeqMananger]")
  SeqManager<uint16_t> seqManager(/*initialOutput*/ 1000);
  validate(seqManager, inputs);
  }
+
+ SECTION("receive packets prior to first mapped packet")
+ {
+ // clang-format off
+ std::vector<TestSeqManagerInput<uint16_t>> inputs =
+ {
+ { 4, 4, false, false },
+ { 3, 3, false, false },
+ { 65535, 65535, false, false },
+ };
+ // clang-format on
+
+ SeqManager<uint16_t> seqManager;
+ validate(seqManager, inputs);
+ }
 }