diff --git a/build.gradle.kts b/build.gradle.kts
index f7a6c34..818ae5b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -27,4 +27,5 @@ java {
 
 tasks.test {
     useJUnitPlatform()
+    jvmArgs = listOf("-Dfast=true")
 }
\ No newline at end of file
diff --git a/padlock-impl/build.gradle.kts b/padlock-impl/build.gradle.kts
index 946892a..66d7554 100644
--- a/padlock-impl/build.gradle.kts
+++ b/padlock-impl/build.gradle.kts
@@ -21,4 +21,5 @@ java {
 
 tasks.test {
     useJUnitPlatform()
+    jvmArgs = listOf("-Dfast=true")
 }
\ No newline at end of file
diff --git a/padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java b/padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java
index 30614c2..3495967 100644
--- a/padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java
+++ b/padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java
@@ -27,7 +27,7 @@ import static com.cleverthis.interview.padlock.Utils.ensureSleep;
  * After create, the input buffer is empty, you have to initialize.
  */
 public class PadlockImpl {
-    private final boolean debug;
+    private final boolean fast = Boolean.parseBoolean(System.getProperty("fast"));
     private final int numpadSize;
     private final Integer[] inputBuffer;
     private final Integer[] correctPasscode;
@@ -38,17 +38,6 @@ public class PadlockImpl {
      * @param numpadSize The number of buttons on the numpad of this lock.
      */
     public PadlockImpl(int numpadSize) {
-        this(numpadSize, false);
-    }
-
-    /**
-     * Create a padlock instance.
-     *
-     * @param numpadSize The number of buttons on the numpad of this lock.
-     * @param debug      Will skip sleep if is true
-     */
-    PadlockImpl(int numpadSize, boolean debug) {
-        this.debug = debug;
         if (numpadSize < 1) throw new IllegalArgumentException("numpadSize must be a positive number");
         this.numpadSize = numpadSize;
         this.inputBuffer = new Integer[numpadSize];
@@ -73,7 +62,7 @@ public class PadlockImpl {
      * @return The old value, null if not initialized.
      */
     public synchronized Integer writeInputBuffer(int address, int keyIndex) {
-        if (!debug) ensureSleep(1000);
+        if (!fast) ensureSleep(1000);
         if (keyIndex < 0 || keyIndex >= numpadSize)
             throw new IllegalArgumentException(
                     "keyIndex out of range. Keypad size: " + numpadSize + ", keyIndex: " + keyIndex);
diff --git a/padlock-impl/src/test/java/com/cleverthis/interview/padlock/PadlockTest.java b/padlock-impl/src/test/java/com/cleverthis/interview/padlock/PadlockTest.java
index b935727..5902d43 100644
--- a/padlock-impl/src/test/java/com/cleverthis/interview/padlock/PadlockTest.java
+++ b/padlock-impl/src/test/java/com/cleverthis/interview/padlock/PadlockTest.java
@@ -22,7 +22,7 @@ class PadlockTest {
 
     @Test
     void testInstantiationRest() {
-        PadlockImpl padlock = new PadlockImpl(5, true);
+        PadlockImpl padlock = new PadlockImpl(5);
         for (int i = 0; i < 5; i++) {
             // ensure input buffer is uninitialized
             // should return null when first set
@@ -34,7 +34,7 @@ class PadlockTest {
 
     @Test
     void testRejectInvalidInput() {
-        PadlockImpl padlock = new PadlockImpl(5, true);
+        PadlockImpl padlock = new PadlockImpl(5);
         for (int i = 0; i < 3; i++) {
             padlock.writeInputBuffer(i, i);
         }
@@ -54,7 +54,7 @@ class PadlockTest {
 
     @Test
     void testRejectInvalidInputBufferAddressAndValue() {
-        PadlockImpl padlock = new PadlockImpl(5, true);
+        PadlockImpl padlock = new PadlockImpl(5);
         // test address
         assertThrows(ArrayIndexOutOfBoundsException.class, () -> padlock.writeInputBuffer(-1, 1));
         assertThrows(ArrayIndexOutOfBoundsException.class, () -> padlock.writeInputBuffer(-10, 1));