Updated tests

src/CharacterFrequencyCounter.java

@@ -60,8 +60,10 @@ 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 +3,23 @@
 import org.junit.jupiter.api.Test;
 
 public class CharacterFrequencyCounterTest {
-
+  @Test
+  public void testLAppears3TimesInHelloWorld(){
+    // arrange
+    CharacterFrequencyCounter counter = new CharacterFrequencyCounter("hello world");
+    // act
+    int actual = counter.getFrequency('l');
+    // assert
+    assertEquals(3, actual);
+  }    
+
+  @Test
+  public void testNonOccurringCharacterPercentageIsZero(){
+    // arrange
+    CharacterFrequencyCounter counter = new CharacterFrequencyCounter("hi there");
+    // act
+    double actualPercent = counter.getRelativePercentage('z');
+    // assert
+    assertEquals(0.0, actualPercent, 0.0001);
+  }    
 }