diff --git a/.travis.yml b/.travis.yml
index 5859f97b..438bf4d0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -107,3 +107,10 @@ script:
   #
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then make clean && make -j2 ARCH=x86-64-modern sanitize=undefined optimize=no debug=yes build > /dev/null && ../tests/instrumented.sh --sanitizer-undefined; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then make clean && make -j2 ARCH=x86-64-modern sanitize=thread    optimize=no debug=yes build > /dev/null && ../tests/instrumented.sh --sanitizer-thread; fi
+
+  #
+  # NNUE testing / TODO should work with debug=yes as well
+  #
+  - export CXXFLAGS="-O1 -fno-inline"
+  - if [ -x "$(command -v valgrind )" ]; then make clean && LDFLAGS="-lstdc++fs"  make -j2 ARCH=x86-64-modern debug=no optimize=no learn > /dev/null && ../tests/instrumented_learn.sh --valgrind; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then make clean && LDFLAGS="-lstdc++fs"  make -j2 ARCH=x86-64-modern sanitize=undefined optimize=no debug=no learn > /dev/null && ../tests/instrumented_learn.sh --sanitizer-undefined; fi
diff --git a/src/learn/learner.cpp b/src/learn/learner.cpp
index a5e36e4c..f9e73f8a 100644
--- a/src/learn/learner.cpp
+++ b/src/learn/learner.cpp
@@ -1606,9 +1606,9 @@ namespace Learner
             namespace sys = std::filesystem;
             sys::path kif_base_dir(Path::Combine(base_dir, target_dir)); // Origin of enumeration
             std::for_each(sys::directory_iterator(kif_base_dir), sys::directory_iterator(),
-                [&](const sys::path& p) {
-                    if (sys::is_regular_file(p))
-                        filenames.push_back(Path::Combine(target_dir, p.filename().generic_string()));
+                [&](const sys::path& path) {
+                    if (sys::is_regular_file(path))
+                        filenames.push_back(Path::Combine(target_dir, path.filename().generic_string()));
                 });
         }
 
diff --git a/tests/instrumented_learn.sh b/tests/instrumented_learn.sh
new file mode 100755
index 00000000..756569e6
--- /dev/null
+++ b/tests/instrumented_learn.sh
@@ -0,0 +1,126 @@
+#!/bin/bash
+# check for errors under valgrind or sanitizers.
+
+error()
+{
+  echo "instrumented testing failed on line $1"
+  exit 1
+}
+trap 'error ${LINENO}' ERR
+
+# define suitable post and prefixes for testing options
+case $1 in
+  --valgrind)
+    echo "valgrind testing started"
+    prefix=''
+    exeprefix='valgrind --error-exitcode=42'
+    postfix='1>/dev/null'
+    threads="1"
+  ;;
+  --valgrind-thread)
+    echo "valgrind-thread testing started"
+    prefix=''
+    exeprefix='valgrind --error-exitcode=42'
+    postfix='1>/dev/null'
+    threads="2"
+  ;;
+  --sanitizer-undefined)
+    echo "sanitizer-undefined testing started"
+    prefix='!'
+    exeprefix=''
+    postfix='2>&1 | grep -A50 "runtime error:"'
+    threads="1"
+  ;;
+  --sanitizer-thread)
+    echo "sanitizer-thread testing started"
+    prefix='!'
+    exeprefix=''
+    postfix='2>&1 | grep -A50 "WARNING: ThreadSanitizer:"'
+    threads="2"
+
+cat << EOF > tsan.supp
+race:TTEntry::move
+race:TTEntry::depth
+race:TTEntry::bound
+race:TTEntry::save
+race:TTEntry::value
+race:TTEntry::eval
+race:TTEntry::is_pv
+
+race:TranspositionTable::probe
+race:TranspositionTable::hashfull
+
+EOF
+
+    export TSAN_OPTIONS="suppressions=./tsan.supp"
+
+  ;;
+  *)
+    echo "unknown testing started"
+    prefix=''
+    exeprefix=''
+    postfix=''
+    threads="1"
+  ;;
+esac
+
+mkdir -p training_data_01
+mkdir -p training_data_02
+
+# gensfen testing 01
+cat << EOF > gensfen01.exp
+ set timeout 240
+ spawn $exeprefix ./stockfish
+
+ send "uci\n"
+ expect "uciok"
+
+ send "setoption name Threads value $threads\n"
+ send "setoption name Use NNUE value false\n"
+ send "isready\n"
+ send "gensfen depth 3 loop 100 use_draw_in_training_data_generation 1 eval_limit 32000 output_file_name training_data_01/training_data.bin use_raw_nnue_eval 0\n"
+ expect "gensfen finished."
+
+ send "quit\n"
+ expect eof
+
+ # return error code of the spawned program, useful for valgrind
+ lassign [wait] pid spawnid os_error_flag value
+ exit \$value
+EOF
+
+# gensfen testing 02
+cat << EOF > gensfen02.exp
+ set timeout 240
+ spawn $exeprefix ./stockfish
+
+ send "uci\n"
+ expect "uciok"
+
+ send "setoption name Threads value $threads\n"
+ send "setoption name Use NNUE value true\n"
+ send "isready\n"
+ send "gensfen depth 3 loop 100 use_draw_in_training_data_generation 1 eval_limit 32000 output_file_name training_data_02/training_data.bin use_raw_nnue_eval 0\n"
+ expect "gensfen finished."
+
+ send "quit\n"
+ expect eof
+
+ # return error code of the spawned program, useful for valgrind
+ lassign [wait] pid spawnid os_error_flag value
+ exit \$value
+EOF
+
+for exp in gensfen01.exp gensfen02.exp
+do
+
+  echo "$prefix expect $exp $postfix"
+  eval "$prefix expect $exp $postfix"
+
+  rm $exp
+
+done
+
+rm -f tsan.supp
+
+echo "instrumented learn testing OK"