diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 5758d85..08b98ca 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -25,6 +25,9 @@ jobs:
            mkdir -p build_linux && cd build_linux 
            cmake ..
            make
-           # simple test to make sure the code runs
-           cd src && sox ../../wav/wia.wav -t raw -r 16000 - | ./lpcnet_enc -s | ./lpcnet_dec -s > /dev/null
 
+    - name: Run ctests
+      shell: bash
+      run: |
+           cd build_linux 
+           ctest -V --output-on-failure
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ba2339b..c52d830 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -178,16 +178,26 @@ add_subdirectory(src)
 include(CTest)
 enable_testing()
 
-add_test(NAME core_synthesis_default
-         COMMAND sh -c "cd ${CMAKE_CURRENT_SOURCE_DIR}/unittest; SYNTH=1 ./test_core_nn.sh")
-add_test(NAME core_synthesis_load_20h
-         COMMAND sh -c "cd ${CMAKE_CURRENT_SOURCE_DIR}/unittest; SYNTH_20h=1 ./test_core_nn.sh")
-add_test(NAME core_synthesis_mag
-         COMMAND sh -c "cd ${CMAKE_CURRENT_SOURCE_DIR}/unittest; SYNTH_mag=1 ./test_core_nn.sh")
+# some basic tests - unfortunately the core NN synthsis is hard to test reliably as we get
+# different results on different runs due to numerical/precision issues
+add_test(NAME feature_extraction
+         COMMAND sh -c "PATH=$PATH:${CMAKE_CURRENT_BINARY_DIR}/src:${CMAKE_CURRENT_BINARY_DIR}/unittest;
+                        cd ${CMAKE_CURRENT_SOURCE_DIR}/unittest; 
+                        pwd;
+                        dump_data --test --c2pitch ${CMAKE_CURRENT_SOURCE_DIR}/wav/birch.wav birch.f32;
+                        md5sum birch.f32;
+                        md5sum birch_targ.f32;
+                        diff32 --cont birch_targ.f32 birch.f32")
 add_test(NAME nnet2f32
          COMMAND sh -c "cd ${CMAKE_CURRENT_BINARY_DIR}; ./src/nnet2f32 t.f32")
 add_test(NAME SIMD_functions
          COMMAND sh -c "cd ${CMAKE_CURRENT_BINARY_DIR}; ./src/test_vec")
+add_test(NAME lpcnet_enc_dec
+         COMMAND sh -c "PATH=$PATH:${CMAKE_CURRENT_BINARY_DIR}/src;
+                        cd ${CMAKE_CURRENT_SOURCE_DIR};
+                        sox wav/wia.wav -t raw -r 16000 - | 
+                        lpcnet_enc -s | 
+                        lpcnet_dec -s > /dev/null")
 
 # Packaging
 set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Next-Generation Digital Voice for Two-Way Radio")
diff --git a/src/diff32.c b/src/diff32.c
index b0b95e5..a84bf9e 100644
--- a/src/diff32.c
+++ b/src/diff32.c
@@ -1,4 +1,8 @@
-/* test tool to diffs two .f32 files */
+/* Test tool to diff two float (.f32) files that hold LPCNet
+   "features".  Each file can be seen as a matrix, where each row has
+   "stride" columns.  We calculate the "SNR" of each col measured
+   between the two files, as each col represents a specific feature
+   that will have it's own scaling. */
 
 #include <assert.h>
 #include <math.h>
@@ -6,10 +10,11 @@
 #include <stdlib.h>
 #include <getopt.h>
 
-#define NB_FEATURES 55
+#define NB_FEATURES   55
+#define FDIFF_THRESH  0.001
+#define SNR_THRESH    1000.0
 
 int main(int argc, char *argv[]) {
-    float fdiff, fdiff_tot=0.0;
     int f=0;
     unsigned int ret, i, stride = NB_FEATURES, cont = 0;
 
@@ -56,21 +61,39 @@ int main(int argc, char *argv[]) {
 	exit(1);
     }
 
-    float f1[stride],f2[stride];
+    float fdiff;
+    float f1[stride], f2[stride], s[stride], n[stride];
+    for(i=0; i<stride; i++) {s[i] = 0.0; n[i] = 0.0; }
+    
     while(fread(&f1,sizeof(float),stride,file1) == stride) {
         ret = fread(&f2,sizeof(float),stride,file2);
         if (ret != stride) break;
         for(i=0; i<stride; i++) {
+            s[i] += f1[i]*f1[i];
             fdiff = fabs(f1[i]-f2[i]);
-            fdiff_tot += fdiff;
-            
-            if (isnan(fdiff) || (fdiff > 1E-3)) {
-                printf("f: %d i: %d %f %f %f\n", f, i, f1[i], f2[i], fdiff);
-                if (cont == 0) exit(0);
+            n[i] += fdiff*fdiff;
+
+            /* flag any gross errors straight away */
+            if (isnan(fdiff) || (fdiff > FDIFF_THRESH)) {
+                fprintf(stderr, "f: %d i: %d %f %f %f\n", f, i, f1[i], f2[i], fdiff);
+                if (cont == 0) exit(1);
             }
         }
         f++;
     }
-    fprintf(stderr,"stride: %d f: %d fdiff_tot: %f\n", stride, f, fdiff_tot);
+
     fclose(file1); fclose(file2);
+
+    /* calculate per col SNRs, as each feature might have a different scaling */
+    float snr_min = 1E32;
+    for(i=0; i<stride; i++) {
+        float snr = s[i]/(n[i]+1E-12);
+        if ((s[i] != 0) && (snr < snr_min)) snr_min = snr;
+        fprintf(stderr, "i: %d s: %e n: %e SNR: %e %e\n",  i, s[i], n[i], snr, snr_min);
+    }   
+    
+    if (snr_min > SNR_THRESH)
+        exit(0);
+    else
+        exit(1);
 }
diff --git a/src/dump_data.c b/src/dump_data.c
index 4e8d3c4..2a76f41 100644
--- a/src/dump_data.c
+++ b/src/dump_data.c
@@ -438,7 +438,9 @@ int main(int argc, char **argv) {
       g = f*speech_gain + (1-f)*old_speech_gain;
       x[i] *= g;
     }
-    for (i=0;i<FRAME_SIZE;i++) x[i] += rand()/(float)RAND_MAX - .5;
+    if (training) {
+        for (i=0;i<FRAME_SIZE;i++) x[i] += rand()/(float)RAND_MAX - .5;
+    }
     compute_frame_features(st, X, P, Ex, Ep, Exp, features, x, logmag);
 
     if (c2pitch_en) {
diff --git a/unittest/birch_20h_states_targ.f32 b/unittest/birch_20h_states_targ.f32
deleted file mode 100644
index fccec93..0000000
Binary files a/unittest/birch_20h_states_targ.f32 and /dev/null differ
diff --git a/unittest/birch_20h_targ.raw b/unittest/birch_20h_targ.raw
deleted file mode 100644
index 5203e14..0000000
Binary files a/unittest/birch_20h_targ.raw and /dev/null differ
diff --git a/unittest/birch_mag.f32 b/unittest/birch_mag.f32
deleted file mode 100644
index 97e833e..0000000
Binary files a/unittest/birch_mag.f32 and /dev/null differ
diff --git a/unittest/birch_out_targ.raw b/unittest/birch_out_targ.raw
deleted file mode 100644
index 8ea4bbd..0000000
Binary files a/unittest/birch_out_targ.raw and /dev/null differ
diff --git a/unittest/birch_states_targ.f32 b/unittest/birch_states_targ.f32
deleted file mode 100644
index 41fefdb..0000000
Binary files a/unittest/birch_states_targ.f32 and /dev/null differ
diff --git a/unittest/birch_targ.f32 b/unittest/birch_targ.f32
index 26f5b24..2e495ae 100644
Binary files a/unittest/birch_targ.f32 and b/unittest/birch_targ.f32 differ
diff --git a/unittest/c01_01_190804a_targ.raw b/unittest/c01_01_190804a_targ.raw
deleted file mode 100644
index 65a440e..0000000
Binary files a/unittest/c01_01_190804a_targ.raw and /dev/null differ
diff --git a/unittest/c01_01_mag.f32 b/unittest/c01_01_mag.f32
deleted file mode 100644
index 466adfa..0000000
Binary files a/unittest/c01_01_mag.f32 and /dev/null differ
diff --git a/unittest/lpcnet_190215.f32 b/unittest/lpcnet_190215.f32
deleted file mode 100644
index 4881544..0000000
Binary files a/unittest/lpcnet_190215.f32 and /dev/null differ
diff --git a/unittest/lpcnet_190804a.f32 b/unittest/lpcnet_190804a.f32
deleted file mode 100644
index 9e38953..0000000
Binary files a/unittest/lpcnet_190804a.f32 and /dev/null differ
diff --git a/unittest/lpcnet_20h.f32 b/unittest/lpcnet_20h.f32
deleted file mode 100644
index 28a8900..0000000
Binary files a/unittest/lpcnet_20h.f32 and /dev/null differ
diff --git a/unittest/test_core_nn.sh b/unittest/test_core_nn.sh
deleted file mode 100755
index cd955c7..0000000
--- a/unittest/test_core_nn.sh
+++ /dev/null
@@ -1,68 +0,0 @@
-#!/bin/bash -x
-# test_core_nn.sh
-#
-
-# Some tests for core NN, e.g. generation of test data using
-# dump_data, and unquantised synthesis using and test_lpcnet.  Used to
-# ensure no existing features are broken during experimentation and
-# development.
-
-# test generation of training data (doesn't really test training as that takes hours)
-# TODO: This test not working yet
-if [ ! -z $TRAIN_TEST ]; then
-    TRAIN_SRC=all_speech
-    TRAIN_OUT_PCM=$(mktemp).pcm
-    TRAIN_OUT_F32=$(mktemp).f32
-    TRAIN_TARG_PCM=all_speech.pcm
-    TRAIN_TARG_F32=all_speech.f32
-    ../build_linux/src/dump_data --train --c2pitch -z 0 -n 1E6 ~/Downloads/$TRAIN_SRC.sw $TRAIN_OUT_F32 $TRAIN_OUT_PCM
-    diff $TRAIN_OUT_F32 $TRAIN_TARG_F32 || { echo "ERROR in train .f32 output! Exiting..."; exit 1; }
-    echo "train .f32 OK"
-    diff $TRAIN_OUT_PCM $TRAIN_TARG_PCM || { echo "ERROR in train .pcm output! Exiting..."; exit 1; }
-    echo "train .pcm OK"
-fi
-
-# Basic synthesis with compiled-in in network
-
-if [ ! -z $SYNTH ]; then
-    ../build_linux/src/dump_data --test --c2pitch ../wav/birch.wav birch.f32
-    diff birch_targ.f32 birch.f32 || { echo "ERROR in synth .f32 output! Exiting..."; exit 1; }
-    echo "synth .f32 OK"
-    ../build_linux/src/test_lpcnet -l birch_states.f32 birch.f32 birch_out.raw
-    octave -p ../src --no-gui <<< "ret=compare_states('birch_states_targ.f32', 'birch_states.f32'); quit(ret)"
-    if [ ! $? -eq 0 ]; then { echo "ERROR in synth states Octave output! Exiting..."; exit 1; } fi
-    echo "synth states Octave OK"			    
-    diff birch_states_targ.f32 birch_states.f32 || { echo "ERROR in synth states output! Exiting ..."; exit 1; }
-    echo "synth states OK"
-    diff birch_out_targ.raw birch_out.raw || { echo "ERROR in synth .raw output! Exiting..."; exit 1; }
-    echo "synth .raw OK"
-fi
-
-# Synthesis with the 20h network, loaded up at run time
-    
-if [ ! -z $SYNTH_20h ]; then
-    ../build_linux/src/dump_data --test --c2pitch ../wav/birch.wav birch.f32
-    diff birch_targ.f32 birch.f32 || { echo "ERROR in synth .f32 output! Exiting..."; exit 1; }
-    echo "synth .f32 OK"
-    ../build_linux/src/test_lpcnet -n lpcnet_20h.f32 -l birch_states.f32 birch.f32 birch_out.raw
-    octave -p ../src --no-gui <<< "ret=compare_states('birch_20h_states_targ.f32', 'birch_states.f32'); quit(ret)"
-    if [ ! $? -eq 0 ]; then { echo "ERROR in synth states Octave output! Exiting..."; exit 1; } fi
-    echo "synth states Octave OK"			    
-    diff birch_20h_states_targ.f32 birch_states.f32 || { echo "ERROR in synth states output! Exiting ..."; exit 1; }
-    echo "synth states OK"
-    diff birch_20h_targ.raw birch_out.raw || { echo "ERROR in synth .raw output! Exiting..."; exit 1; }
-    echo "synth .raw OK"
-fi
-
-# Testing log mag operation, using 190804a network.  Not checking states in this test
-    
-if [ ! -z $SYNTH_mag ]; then
-    ../build_linux/src/dump_data --mag --test --c2pitch ../wav/c01_01.wav c01_01.f32
-    diff c01_01_mag.f32 c01_01.f32 || { echo "ERROR in synth .f32 output! Exiting..."; exit 1; }
-    echo "mag .f32 OK"
-    ../build_linux/src/test_lpcnet --mag 1 -n lpcnet_190804a.f32 c01_01.f32 c01_01_out.raw
-    diff c01_01_190804a_targ.raw c01_01_out.raw || { echo "ERROR in synth .raw output! Exiting..."; exit 1; }
-    echo "mag .raw OK"
-fi
-
-echo "all tests PASSED"