Add tests, remove main & print methods in CoinChange.java (TheAlgorithms#5642)

Author: Hardvan

DIRECTORY.md

@@ -786,6 +786,7 @@
             * [BruteForceKnapsackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/BruteForceKnapsackTest.java)
             * [CatalanNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/CatalanNumberTest.java)
             * [ClimbStairsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/ClimbStairsTest.java)
+            * [CoinChangeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/CoinChangeTest.java)
             * [CountFriendsPairingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/CountFriendsPairingTest.java)
             * [EditDistanceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EditDistanceTest.java)
             * [EggDroppingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/EggDroppingTest.java)

src/main/java/com/thealgorithms/dynamicprogramming/CoinChange.java

@@ -7,15 +7,6 @@ public final class CoinChange {
     private CoinChange() {
     }
 
-    // Driver Program
-    public static void main(String[] args) {
-        int amount = 12;
-        int[] coins = {2, 4, 5};
-
-        System.out.println("Number of combinations of getting change for " + amount + " is: " + change(coins, amount));
-        System.out.println("Minimum number of coins required for amount :" + amount + " is: " + minimumCoins(coins, amount));
-    }
-
     /**
      * This method finds the number of combinations of getting change for a
      * given amount and change coins
@@ -32,8 +23,6 @@ public static int change(int[] coins, int amount) {
             for (int i = coin; i < amount + 1; i++) {
                 combinations[i] += combinations[i - coin];
             }
-            // Uncomment the below line to see the state of combinations for each coin
-            // printAmount(combinations);
         }
 
         return combinations[amount];
@@ -65,16 +54,7 @@ public static int minimumCoins(int[] coins, int amount) {
                 }
             }
         }
-        // Uncomment the below line to see the state of combinations for each coin
-        // printAmount(minimumCoins);
-        return minimumCoins[amount];
-    }
 
-    // A basic print method which prints all the contents of the array
-    public static void printAmount(int[] arr) {
-        for (int i = 0; i < arr.length; i++) {
-            System.out.print(arr[i] + " ");
-        }
-        System.out.println();
+        return minimumCoins[amount];
     }
 }

src/test/java/com/thealgorithms/dynamicprogramming/CoinChangeTest.java

@@ -0,0 +1,80 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class CoinChangeTest {
+
+    @Test
+    void testChangeBasic() {
+        int amount = 12;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(5, CoinChange.change(coins, amount));
+    }
+
+    @Test
+    void testChangeNoCoins() {
+        int amount = 12;
+        int[] coins = {};
+
+        assertEquals(0, CoinChange.change(coins, amount));
+    }
+
+    @Test
+    void testChangeNoAmount() {
+        int amount = 0;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(1, CoinChange.change(coins, amount));
+    }
+
+    @Test
+    void testChangeImpossibleAmount() {
+        int amount = 3;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(0, CoinChange.change(coins, amount));
+    }
+
+    @Test
+    void testMinimumCoinsBasic() {
+        int amount = 12;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(3, CoinChange.minimumCoins(coins, amount));
+    }
+
+    @Test
+    void testMinimumCoinsNoCoins() {
+        int amount = 12;
+        int[] coins = {};
+
+        assertEquals(Integer.MAX_VALUE, CoinChange.minimumCoins(coins, amount));
+    }
+
+    @Test
+    void testMinimumCoinsNoAmount() {
+        int amount = 0;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(0, CoinChange.minimumCoins(coins, amount));
+    }
+
+    @Test
+    void testMinimumCoinsImpossibleAmount() {
+        int amount = 3;
+        int[] coins = {2, 4, 5};
+
+        assertEquals(Integer.MAX_VALUE, CoinChange.minimumCoins(coins, amount));
+    }
+
+    @Test
+    void testMinimumCoinsExactAmount() {
+        int amount = 10;
+        int[] coins = {1, 5, 10};
+
+        assertEquals(1, CoinChange.minimumCoins(coins, amount));
+    }
+}