Refactor BCD Conversion docs and add more tests (#5762)

src/test/java/com/thealgorithms/bitmanipulation/BcdConversionTest.java

@@ -1,65 +1,85 @@
 package com.thealgorithms.bitmanipulation;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
-/**
- * Unit tests for the BcdConversion class.
- */
 public class BcdConversionTest {
 
-    /**
-     * Test the bcdToBinary method with a BCD number.
-     */
     @Test
-    public void testBcdToBinary() {
-        int binary = BcdConversion.bcdToBinary(0x1234);
-        assertEquals(1234, binary); // BCD 0x1234 should convert to binary 1234
+    public void testBcdToDecimal() {
+        int decimal = BcdConversion.bcdToDecimal(0x1234);
+        assertEquals(1234, decimal); // BCD 0x1234 should convert to decimal 1234
     }
 
-    /**
-     * Test the binaryToBcd method with a binary number.
-     */
     @Test
-    public void testBinaryToBcd() {
-        int bcd = BcdConversion.binaryToBcd(1234);
-        assertEquals(0x1234, bcd); // Binary 1234 should convert to BCD 0x1234
+    public void testDecimalToBcd() {
+        int bcd = BcdConversion.decimalToBcd(1234);
+        assertEquals(0x1234, bcd); // Decimal 1234 should convert to BCD 0x1234
     }
 
-    /**
-     * Test the bcdToBinary method with zero.
-     */
     @Test
-    public void testBcdToBinaryZero() {
-        int binary = BcdConversion.bcdToBinary(0x0);
-        assertEquals(0, binary); // BCD 0x0 should convert to binary 0
+    public void testBcdToDecimalZero() {
+        int decimal = BcdConversion.bcdToDecimal(0x0);
+        assertEquals(0, decimal); // BCD 0x0 should convert to decimal 0
     }
 
-    /**
-     * Test the binaryToBcd method with zero.
-     */
     @Test
-    public void testBinaryToBcdZero() {
-        int bcd = BcdConversion.binaryToBcd(0);
-        assertEquals(0x0, bcd); // Binary 0 should convert to BCD 0x0
+    public void testDecimalToBcdZero() {
+        int bcd = BcdConversion.decimalToBcd(0);
+        assertEquals(0x0, bcd); // Decimal 0 should convert to BCD 0x0
     }
 
-    /**
-     * Test the bcdToBinary method with a single digit BCD number.
-     */
     @Test
-    public void testBcdToBinarySingleDigit() {
-        int binary = BcdConversion.bcdToBinary(0x7);
-        assertEquals(7, binary); // BCD 0x7 should convert to binary 7
+    public void testBcdToDecimalSingleDigit() {
+        int decimal = BcdConversion.bcdToDecimal(0x7);
+        assertEquals(7, decimal); // BCD 0x7 should convert to decimal 7
     }
 
-    /**
-     * Test the binaryToBcd method with a single digit binary number.
-     */
     @Test
-    public void testBinaryToBcdSingleDigit() {
-        int bcd = BcdConversion.binaryToBcd(7);
-        assertEquals(0x7, bcd); // Binary 7 should convert to BCD 0x7
+    public void testDecimalToBcdSingleDigit() {
+        int bcd = BcdConversion.decimalToBcd(7);
+        assertEquals(0x7, bcd); // Decimal 7 should convert to BCD 0x7
+    }
+
+    @Test
+    public void testBcdToDecimalMaxValue() {
+        int decimal = BcdConversion.bcdToDecimal(0x9999);
+        assertEquals(9999, decimal); // BCD 0x9999 should convert to decimal 9999
+    }
+
+    @Test
+    public void testDecimalToBcdMaxValue() {
+        int bcd = BcdConversion.decimalToBcd(9999);
+        assertEquals(0x9999, bcd); // Decimal 9999 should convert to BCD 0x9999
+    }
+
+    @Test
+    public void testBcdToDecimalInvalidHighDigit() {
+        // Testing invalid BCD input where one of the digits is > 9
+        assertThrows(IllegalArgumentException.class, () -> {
+            BcdConversion.bcdToDecimal(0x123A); // Invalid BCD, 'A' is not a valid digit
+        });
+    }
+
+    @Test
+    public void testDecimalToBcdInvalidValue() {
+        // Testing conversion for numbers greater than 9999, which cannot be represented in BCD
+        assertThrows(IllegalArgumentException.class, () -> {
+            BcdConversion.decimalToBcd(10000); // 10000 is too large for BCD representation
+        });
+    }
+
+    @Test
+    public void testBcdToDecimalLeadingZeroes() {
+        int decimal = BcdConversion.bcdToDecimal(0x0234);
+        assertEquals(234, decimal); // BCD 0x0234 should convert to decimal 234, ignoring leading zero
+    }
+
+    @Test
+    public void testDecimalToBcdLeadingZeroes() {
+        int bcd = BcdConversion.decimalToBcd(234);
+        assertEquals(0x0234, bcd); // Decimal 234 should convert to BCD 0x0234
     }
 }