diff --git a/test/hei_user_defines.cpp b/test/hei_user_defines.cpp
deleted file mode 100644
index f6e39f0..0000000
--- a/test/hei_user_defines.cpp
+++ /dev/null
@@ -1,30 +0,0 @@
-#include <assert.h>
-#include <stdarg.h>
-#include <stdio.h>
-
-namespace libhei
-{
-
-void hei_inf(char* format, ...)
-{
-    va_list args;
-
-    printf("I> ");
-    va_start(args, format);
-    vprintf(format, args);
-    va_end(args);
-    printf("\n");
-}
-
-void hei_err(char* format, ...)
-{
-    va_list args;
-
-    printf("E> ");
-    va_start(args, format);
-    vprintf(format, args);
-    va_end(args);
-    printf("\n");
-}
-
-} // namespace libhei
diff --git a/test/meson.build b/test/meson.build
index 209bad3..642b827 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -3,7 +3,7 @@
 
 # supporting files that need compiled/linked
 test_src = ['../src/util/hei_bit_string.cpp',
-               'hei_user_defines.cpp']
+            'sim_tracing.cpp']
 
 # build g-test framework unit tests
 gtests = [
diff --git a/test/sim_tracing.cpp b/test/sim_tracing.cpp
new file mode 100644
index 0000000..f3ac008
--- /dev/null
+++ b/test/sim_tracing.cpp
@@ -0,0 +1,29 @@
+#include <stdarg.h>
+#include <stdio.h>
+
+namespace libhei
+{
+
+// prints a single line to stdout
+void hei_inf(char* format, ...)
+{
+    va_list args;
+    fprintf(stdout, "I> ");
+    va_start(args, format);
+    vfprintf(stdout, format, args);
+    va_end(args);
+    fprintf(stdout, "\n");
+}
+
+// prints a single line to stderr
+void hei_err(char* format, ...)
+{
+    va_list args;
+    fprintf(stderr, "E> ");
+    va_start(args, format);
+    vfprintf(stderr, format, args);
+    va_end(args);
+    fprintf(stderr, "\n");
+}
+
+} // namespace libhei
diff --git a/test/simulator/meson.build b/test/simulator/meson.build
index ec5410f..590e381 100644
--- a/test/simulator/meson.build
+++ b/test/simulator/meson.build
@@ -1,12 +1,12 @@
 # Simulator sources
-sim_libhei = [
+sim_src = [
     'simulator.cpp',
-    'hei_user_interface.cpp',
-    '../hei_user_defines.cpp'
+    'sim_hardware_access.cpp',
+    '../sim_tracing.cpp'
 ]
 
 # Test cases
-test_libhei = [
+test_src = [
     'sample_test_case.cpp',
 ]
 
@@ -15,7 +15,7 @@
 # Build simulator linked locally
 if gtest.found()
     test('simulator',
-         executable('simulator', sim_libhei, test_libhei,
+         executable('simulator', sim_src, test_src,
                     dependencies : gtest,
                     link_with : libhei_static,
                     include_directories: incdir))
diff --git a/test/simulator/hei_user_interface.cpp b/test/simulator/sim_hardware_access.cpp
similarity index 100%
rename from test/simulator/hei_user_interface.cpp
rename to test/simulator/sim_hardware_access.cpp