diff --git a/tests/unit/modules/stubs/stub_shr16.cpp b/tests/unit/modules/stubs/stub_shr16.cpp
index 45bcf30..97d179f 100644
--- a/tests/unit/modules/stubs/stub_shr16.cpp
+++ b/tests/unit/modules/stubs/stub_shr16.cpp
@@ -6,20 +6,29 @@ namespace shr16 {
 SHR16 shr16;
 
 uint16_t shr16_v_copy;
+uint8_t shr16_tmc_dir;
 
 void SHR16::Init() {
     shr16_v_copy = 0;
+    shr16_tmc_dir = 0;
 }
 
 void SHR16::SetLED(uint16_t led) {
     shr16_v_copy = ((led & 0x00ff) << 8) | ((led & 0x0300) >> 2);
 }
+
 void SHR16::SetTMCEnabled(uint8_t index, bool ena) {
     // do nothing right now
 }
+
 void SHR16::SetTMCDir(uint8_t index, bool dir) {
-    // do nothing right now
+    // this is using another array for testing convenience
+    if (dir)
+        shr16_tmc_dir |= (1 << index);
+    else
+        shr16_tmc_dir &= ~(1 << index);
 }
+
 void SHR16::Write(uint16_t v) {
     // do nothing right now
 }