add test for handling no occurrences of a character in countChar function

Author: CatchingKiyoko

Sprint-3/2-practice-tdd/count.test.js

@@ -22,3 +22,10 @@ test("should count multiple occurrences of a character", () => {
 // And a character char that does not exist within the case-sensitive str,
 // When the function is called with these inputs,
 // Then it should return 0, indicating that no occurrences of the char were found in the case-sensitive str.
+
+test("should return 0 for no occurrences of a character", () => {
+  const str = "example";
+  const char = "z";
+  const count = countChar(str, char);
+  expect(count).toEqual(0);
+});