Fixed One Bug

src/CharacterFrequencyCounter.java

@@ -60,8 +60,13 @@ public int getFrequency(char c) {
      */
     public double getRelativePercentage(char c) {
         c = Character.toLowerCase(c);
-        int charCount = frequencyMap.get(c);
+        int charCount = 0;
+        if(frequencyMap.get(c) != null)
+        {
+            charCount = frequencyMap.get(c);
+        }
 
+
         return ((double) charCount / totalCharacterCount) * 100;
     }
 }

src/CharacterFrequencyCounterTest.java

@@ -3,5 +3,27 @@
 import org.junit.jupiter.api.Test;
 
 public class CharacterFrequencyCounterTest {
-
+    @Test
+    public void testLAppearsThreeTimesInHelloWorld()
+    {
+        //arrange: set up test
+        CharacterFrequencyCounter counter = new CharacterFrequencyCounter("hello world");
+
+        //act: making something happen calling a method usually
+        int actualCount = counter.getFrequency('l');
+
+        //assert: get results and check that they match expected results
+        assertEquals(3, actualCount);
+
+    }
+
+    @Test
+    public void testNoneOccurringCharacterPercentageIsZero()
+    {
+        CharacterFrequencyCounter counter = new CharacterFrequencyCounter("hi there");
+
+        double actualPercentage = counter.getRelativePercentage('z');
+
+        assertEquals(0.0, actualPercentage, 0.001);
+    }
 }