Add NodeDB tests around FindClosestTo()

test/CMakeLists.txt

@@ -78,6 +78,7 @@ if(${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
 endif()
 
 add_executable(${CHECK_EXE}
+  nodedb/test_nodedb.cpp
   path/test_path.cpp
   check_main.cpp)
 

test/nodedb/test_nodedb.cpp

@@ -0,0 +1,68 @@
+#include "catch.hpp"
+#include "config/config.hpp"
+
+#include <router_contact.hpp>
+#include <nodedb.hpp>
+
+TEST_CASE("FindClosestTo returns correct number of elements", "[nodedb][dht]")
+{
+
+  llarp_nodedb nodeDB(nullptr, "");
+
+  constexpr uint64_t numRCs = 3;
+  for (uint64_t i=0; i<numRCs; ++i)
+  {
+    llarp::RouterContact rc;
+    rc.pubkey[0] = i;
+    nodeDB.Insert(rc);
+  }
+
+  REQUIRE(numRCs == nodeDB.num_loaded());
+
+  llarp::dht::Key_t key;
+
+  std::vector< llarp::RouterContact > results = nodeDB.FindClosestTo(key, 4);
+
+  // we asked for more entries than nodedb had
+  REQUIRE(numRCs == results.size());
+}
+
+TEST_CASE("FindClosestTo returns properly ordered set", "[nodedb][dht]")
+{
+
+  llarp_nodedb nodeDB(nullptr, "");
+
+  // insert some RCs: a < b < c
+  llarp::RouterContact a;
+  a.pubkey[0] = 1;
+  nodeDB.Insert(a);
+
+  llarp::RouterContact b;
+  b.pubkey[0] = 2;
+  nodeDB.Insert(b);
+
+  llarp::RouterContact c;
+  c.pubkey[0] = 3;
+  nodeDB.Insert(c);
+
+  REQUIRE(3 == nodeDB.num_loaded());
+
+  llarp::dht::Key_t key;
+
+  std::vector< llarp::RouterContact > results = nodeDB.FindClosestTo(key, 2);
+  REQUIRE(2 == results.size());
+
+  // we xor'ed with 0x0, so order should be a,b,c
+  REQUIRE(a.pubkey == results[0].pubkey);
+  REQUIRE(b.pubkey == results[1].pubkey);
+
+  llarp::dht::Key_t compKey;
+  compKey.Fill(0xFF);
+
+  results = nodeDB.FindClosestTo(compKey, 2);
+
+  // we xor'ed with 0xF...F, so order should be inverted (c,b,a)
+  REQUIRE(c.pubkey == results[0].pubkey);
+  REQUIRE(b.pubkey == results[1].pubkey);
+}
+