added test for hexStrLen function

test/conversionOfNumbers/test_conversionOfNumbers.c

@@ -141,3 +141,15 @@ void test_convert12ToHexStrC(){
     TEST_ASSERT_EQUAL_STRING(expected, result);
     free(result);
 }
+
+void test_binaryStringLengthOfInput256is3(){
+    //arrange
+    int result;
+    int expected = 3;
+
+    //act
+    result = hexStrLen(256);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected, result);
+}