diff --git a/Firmware/Marlin_main.cpp b/Firmware/Marlin_main.cpp
index 7c06981f7..dc2a58818 100644
--- a/Firmware/Marlin_main.cpp
+++ b/Firmware/Marlin_main.cpp
@@ -3327,10 +3327,10 @@ static void mmu_M600_filament_change_screen(uint8_t eject_slot) {
         manage_heater();
         manage_inactivity(true);
 
-        btn = MMU2::mmu2.getPrinterButtonOperation();
+        btn = MMU2::mmu2.GetPrinterButtonOperation();
         if (btn != MMU2::Buttons::NoButton)
         {
-            MMU2::mmu2.clearPrinterButtonOperation();
+            MMU2::mmu2.ClearPrinterButtonOperation();
 
             if (btn == MMU2::Buttons::Eject) {
                 if (eject_slot != (uint8_t)MMU2::FILAMENT_UNKNOWN) {
diff --git a/Firmware/mmu2.cpp b/Firmware/mmu2.cpp
index 15c42915b..1ec53e6e4 100644
--- a/Firmware/mmu2.cpp
+++ b/Firmware/mmu2.cpp
@@ -761,7 +761,7 @@ void MMU2::CheckUserInput() {
     case Buttons::Load:
     case Buttons::Eject:
         // High level operation
-        setPrinterButtonOperation(btn);
+        SetPrinterButtonOperation(btn);
         break;
     case Buttons::ResetMMU:
         Reset(ResetPin); // we cannot do power cycle on the MK3
diff --git a/Firmware/mmu2.h b/Firmware/mmu2.h
index 6040eebb9..750154ce0 100644
--- a/Firmware/mmu2.h
+++ b/Firmware/mmu2.h
@@ -5,14 +5,11 @@
 #include "mmu2_marlin.h"
 
 #ifdef __AVR__
-#include "mmu2_protocol_logic.h"
+    #include "mmu2_protocol_logic.h"
 typedef float feedRate_t;
 
 #else
-
     #include "protocol_logic.h"
-    #include "../../Marlin/src/core/macros.h"
-    #include "../../Marlin/src/core/types.h"
     #include <atomic>
 #endif
 
@@ -48,9 +45,9 @@ public:
 
     /// Different levels of resetting the MMU
     enum ResetForm : uint8_t {
-        Software = 0,   ///< sends a X0 command into the MMU, the MMU will watchdog-reset itself
-        ResetPin = 1,   ///< trigger the reset pin of the MMU
-        CutThePower = 2, ///< power off and power on (that includes +5V and +24V power lines)
+        Software = 0,     ///< sends a X0 command into the MMU, the MMU will watchdog-reset itself
+        ResetPin = 1,     ///< trigger the reset pin of the MMU
+        CutThePower = 2,  ///< power off and power on (that includes +5V and +24V power lines)
         EraseEEPROM = 42, ///< erase MMU EEPROM and then perform a software reset
     };
 
@@ -201,9 +198,9 @@ public:
     };
     inline void InvokeErrorScreen(ErrorCode ec) {
         // The printer may not raise an error when the MMU is busy
-        if ( !logic.CommandInProgress() // MMU must not be busy
+        if (!logic.CommandInProgress()                // MMU must not be busy
             && MMUCurrentErrorCode() == ErrorCode::OK // The protocol must not be in error state
-            && lastErrorCode != ec) // The error code is not a duplicate
+            && lastErrorCode != ec)                   // The error code is not a duplicate
         {
             ReportError(ec, ErrorSource::ErrorSourcePrinter);
         }
@@ -217,21 +214,23 @@ public:
 
     /// @brief Queue a button operation which the printer can act upon
     /// @param btn Button operation
-    inline void setPrinterButtonOperation(Buttons btn) {
+    inline void SetPrinterButtonOperation(Buttons btn) {
         printerButtonOperation = btn;
     }
 
     /// @brief Get the printer button operation
     /// @return currently set printer button operation, it can be NoButton if nothing is queued
-    inline Buttons getPrinterButtonOperation() {
+    inline Buttons GetPrinterButtonOperation() {
         return printerButtonOperation;
     }
 
-    inline void clearPrinterButtonOperation() {
+    inline void ClearPrinterButtonOperation() {
         printerButtonOperation = Buttons::NoButton;
     }
 
+#ifndef UNITTEST
 private:
+#endif
     /// Perform software self-reset of the MMU (sends an X0 command)
     void ResetX0();
 
@@ -279,6 +278,11 @@ private:
 
     /// Responds to a change of MMU's progress
     /// - plans additional steps, e.g. starts the E-motor after fsensor trigger
+    /// The function is quite complex, because it needs to handle asynchronnous
+    /// progress and error reports coming from the MMU without an explicit command
+    /// - typically after MMU's start or after some HW issue on the MMU.
+    /// It must ensure, that calls to @ref ReportProgress and/or @ref ReportError are
+    /// only executed after @ref BeginReport has been called first.
     void OnMMUProgressMsg(ProgressCode pc);
     /// Progress code changed - act accordingly
     void OnMMUProgressMsgChanged(ProgressCode pc);