testing: improving CRCAlgorithmTest (#6403)

* testing: improving CRCAlgorithmTest

* style: fix formatting

---------

Co-authored-by: Deniz Altunkapan <[email protected]>

Author: alxkm

src/test/java/com/thealgorithms/others/CRCAlgorithmTest.java

@@ -1,29 +1,82 @@
-
 package com.thealgorithms.others;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.Test;
 
 public class CRCAlgorithmTest {
 
     @Test
-    void test1() {
+    void testNoErrorsWithZeroBER() {
         CRCAlgorithm c = new CRCAlgorithm("10010101010100101010010000001010010101010", 10, 0.0);
-
-        // A bit-error rate of 0.0 should not provide any wrong messages
-        c.changeMess();
+        c.generateRandomMess();
         c.divideMessageWithP(false);
-        assertEquals(c.getWrongMess(), 0);
+        c.changeMess();
+        c.divideMessageWithP(true);
+        assertEquals(0, c.getWrongMess(), "BER=0 should produce no wrong messages");
+        assertEquals(0, c.getWrongMessCaught(), "No errors, so no caught wrong messages");
+        assertEquals(0, c.getWrongMessNotCaught(), "No errors, so no uncaught wrong messages");
+        assertTrue(c.getCorrectMess() > 0, "Should have some correct messages");
     }
 
     @Test
-    void test2() {
+    void testAllErrorsWithBEROne() {
         CRCAlgorithm c = new CRCAlgorithm("10010101010100101010010000001010010101010", 10, 1.0);
+        c.generateRandomMess();
+        c.divideMessageWithP(false);
+        c.changeMess();
+        c.divideMessageWithP(true);
+        assertTrue(c.getWrongMess() > 0, "BER=1 should produce wrong messages");
+        assertEquals(0, c.getCorrectMess(), "BER=1 should produce no correct messages");
+    }
 
-        // A bit error rate of 1.0 should not provide any correct messages
+    @Test
+    void testIntermediateBER() {
+        CRCAlgorithm c = new CRCAlgorithm("1101", 4, 0.5);
+        c.generateRandomMess();
+        for (int i = 0; i < 1000; i++) {
+            c.refactor();
+            c.generateRandomMess();
+            c.divideMessageWithP(false);
+            c.changeMess();
+            c.divideMessageWithP(true);
+        }
+        assertTrue(c.getWrongMess() > 0, "Some wrong messages expected with BER=0.5");
+        assertTrue(c.getWrongMessCaught() >= 0, "Wrong messages caught counter >= 0");
+        assertTrue(c.getWrongMessNotCaught() >= 0, "Wrong messages not caught counter >= 0");
+        assertTrue(c.getCorrectMess() >= 0, "Correct messages counter >= 0");
+        assertEquals(c.getWrongMess(), c.getWrongMessCaught() + c.getWrongMessNotCaught(), "Sum of caught and not caught wrong messages should equal total wrong messages");
+    }
+
+    @Test
+    void testMessageChangedFlag() {
+        CRCAlgorithm c = new CRCAlgorithm("1010", 4, 1.0);
+        c.generateRandomMess();
+        c.divideMessageWithP(false);
+        c.changeMess();
+        assertTrue(c.getWrongMess() > 0, "Message should be marked as changed with BER=1");
+    }
+
+    @Test
+    void testSmallMessageSize() {
+        CRCAlgorithm c = new CRCAlgorithm("11", 2, 0.0);
+        c.generateRandomMess();
+        c.divideMessageWithP(false);
         c.changeMess();
+        c.divideMessageWithP(true);
+        assertEquals(0, c.getWrongMess(), "No errors expected for BER=0 with small message");
+    }
+
+    @Test
+    void testLargeMessageSize() {
+        CRCAlgorithm c = new CRCAlgorithm("1101", 1000, 0.01);
+        c.generateRandomMess();
         c.divideMessageWithP(false);
-        assertEquals(c.getCorrectMess(), 0);
+        c.changeMess();
+        c.divideMessageWithP(true);
+        // Just ensure counters are updated, no exceptions
+        assertTrue(c.getWrongMess() >= 0);
+        assertTrue(c.getCorrectMess() >= 0);
     }
 }