diff --git a/src/main/java/jace/core/SoundMixer.java b/src/main/java/jace/core/SoundMixer.java
index 8197eb6..55ebb5b 100644
--- a/src/main/java/jace/core/SoundMixer.java
+++ b/src/main/java/jace/core/SoundMixer.java
@@ -61,6 +61,9 @@ public class SoundMixer extends Device {
      */
     @ConfigurableField(name = "Playback Rate", shortName = "freq")
     public static int RATE = 48000;
+    @ConfigurableField(name = "Mute", shortName = "mute")
+    public static boolean MUTE = false;
+    
     /**
      * Sound format used for playback
      */
@@ -104,7 +107,9 @@ public class SoundMixer extends Device {
 
     @Override
     public synchronized void reconfigure() {
-        if (isConfigDifferent()) {
+        if (MUTE) {
+            detach();
+        } else if (isConfigDifferent()) {
             detach();
             try {
                 initMixer();
diff --git a/src/main/java/jace/core/Utility.java b/src/main/java/jace/core/Utility.java
index 533be9f..280102f 100644
--- a/src/main/java/jace/core/Utility.java
+++ b/src/main/java/jace/core/Utility.java
@@ -285,6 +285,10 @@ public class Utility {
     public static void setHeadlessMode(boolean headless) {
         isHeadless = headless;
     }
+
+    public static boolean isHeadlessMode() {
+        return isHeadless;
+    }
     
     public static Optional<Image> loadIcon(String filename) {
         if (isHeadless) {
diff --git a/src/test/java/jace/cpu/Basic6502FuncationalityTest.java b/src/test/java/jace/cpu/Basic6502FuncationalityTest.java
index a216314..212de68 100644
--- a/src/test/java/jace/cpu/Basic6502FuncationalityTest.java
+++ b/src/test/java/jace/cpu/Basic6502FuncationalityTest.java
@@ -20,6 +20,7 @@ import jace.apple2e.Apple2e;
 import jace.apple2e.MOS65C02;
 import jace.core.Computer;
 import jace.core.RAM;
+import jace.core.SoundMixer;
 import jace.core.Utility;
 import jace.ide.HeadlessProgram;
 import jace.ide.Program;
@@ -45,10 +46,12 @@ public class Basic6502FuncationalityTest {
     @BeforeClass
     public static void setupClass() {
         Utility.setHeadlessMode(true);
+        SoundMixer.MUTE = true;
         computer = new Apple2e();
         cpu = (MOS65C02) computer.getCpu();
         ram = computer.getMemory();
         Emulator.computer = (Apple2e) computer;
+        computer.pause();
     }
 
     @AfterClass
@@ -57,6 +60,7 @@ public class Basic6502FuncationalityTest {
 
     @Before
     public void setup() {
+        cpu.suspend();
         for (int i = 0; i < 1024; i++) {
             ram.write(i, (byte) 0, false, false);
         }
@@ -74,6 +78,7 @@ public class Basic6502FuncationalityTest {
     public void testAdditionNonDecimal() {
         cpu.A = 0;
         cpu.D = false;
+        cpu.C = 0;
         assemble(" adc #1");
         assertEquals("Nothing should change yet", 0, cpu.A);
         cpu.tick();