diff --git a/padlock-impl/build.gradle.kts b/padlock-impl/build.gradle.kts
index 0aa5bde..946892a 100644
--- a/padlock-impl/build.gradle.kts
+++ b/padlock-impl/build.gradle.kts
@@ -14,6 +14,11 @@ dependencies {
     testImplementation("org.junit.jupiter:junit-jupiter")
 }
 
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
+
 tasks.test {
     useJUnitPlatform()
 }
\ 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 0986289..d6c3de6 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
@@ -27,6 +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 int numpadSize;
     private final Integer[] inputBuffer;
     private final Integer[] correctPasscode;
@@ -37,6 +38,17 @@ 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];
@@ -59,7 +71,7 @@ public class PadlockImpl {
      * @return The old value, null if not initialized.
      */
     public synchronized Integer writeInputBuffer(int address, int keyIndex) {
-        ensureSleep(1000);
+        if (!debug) ensureSleep(1000);
         if (keyIndex < 0 || keyIndex >= numpadSize)
             throw new IllegalArgumentException(
                     "keyIndex out of range. Keypad size: " + numpadSize + ", keyIndex: " + keyIndex);