diff --git a/src/fr/klemek/primedate/MainProcess.java b/src/fr/klemek/primedate/MainProcess.java
index 02359c4..4546819 100644
--- a/src/fr/klemek/primedate/MainProcess.java
+++ b/src/fr/klemek/primedate/MainProcess.java
@@ -15,7 +15,7 @@ import java.util.TimerTask;
  */
 public abstract class MainProcess {
 
-	private final static String VERSION = "v1.2";
+	private final static String VERSION = "v1.3";
 
 	private final static SimpleDateFormat DATE_TO_NUM = new SimpleDateFormat("yyyyMMddHHmm");
 
diff --git a/src/fr/klemek/primedate/PrimeCalculator.java b/src/fr/klemek/primedate/PrimeCalculator.java
index ecab7b9..c808bed 100644
--- a/src/fr/klemek/primedate/PrimeCalculator.java
+++ b/src/fr/klemek/primedate/PrimeCalculator.java
@@ -86,8 +86,10 @@ public abstract class PrimeCalculator {
 		long end = start + BLOCK_MAX;
 		long endSqrt = (long) Math.sqrt(end) + 1;
 
+		System.out.println(number);
+		
 		byte block = 0;
-		int p = 3;
+		int p = 2;
 		while (p < endSqrt) {
 			p = nextPrime(p);
 
@@ -102,6 +104,9 @@ public abstract class PrimeCalculator {
 		}
 		byte mask = (byte) (1 << ((number >> 1) & 7));
 
+		System.out.println(byteToBinary(block));
+		System.out.println(byteToBinary(mask));
+		
 		return !((block & mask) != 0);
 	}
 
@@ -125,5 +130,9 @@ public abstract class PrimeCalculator {
 			return !getBit(number);
 		return isPrimeByBlock(number);
 	}
+	
+	public static String byteToBinary(byte b) {
+		return String.format("%8s", Integer.toBinaryString(b & 0xFF)).replace(' ', '0');
+	}
 
 }
diff --git a/test/fr/klemek/primedate/PrimeCalculatorTests.java b/test/fr/klemek/primedate/PrimeCalculatorTests.java
new file mode 100644
index 0000000..7df54db
--- /dev/null
+++ b/test/fr/klemek/primedate/PrimeCalculatorTests.java
@@ -0,0 +1,44 @@
+package fr.klemek.primedate;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class PrimeCalculatorTests {
+
+	public void testNumber(boolean expected, long number) throws Exception {
+		if(expected)
+			assertTrue(number+" should be prime", PrimeCalculator.isPrime(number));
+		else
+			assertFalse(number+" should not be prime", PrimeCalculator.isPrime(number));
+	}
+	
+	@Test
+	public void testIsPrimeSmall() throws Exception {
+		testNumber(true, 1);
+		testNumber(true, 2);
+		testNumber(true, 3);
+		testNumber(false, 4);
+		testNumber(true, 5);
+		testNumber(false, 6);
+		testNumber(true, 7);
+		testNumber(false, 9);
+	}
+
+	@Test
+	public void testIsPrimeNormal() throws Exception {
+		testNumber(true, 8011);
+		testNumber(true, 8941);
+		testNumber(false, 8943);
+		testNumber(true, 9283);
+	}
+	
+	@Test
+	public void testIsPrimeBig() throws Exception {
+		testNumber(true, 201802181381L);
+		testNumber(false, 201802181383L);
+		testNumber(false, 201802181307L);
+		testNumber(false, 201802181409L);
+		testNumber(true, 201802181411L);
+	}
+}