Add test for String character access Functions

Author: giulcioffi

test/CMakeLists.txt

@@ -45,6 +45,7 @@ set(TEST_SRCS
   src/String/test_concat.cpp
   src/String/test_compareTo.cpp
   src/String/test_comparisonFunc.cpp
+  src/String/test_characterAccessFunc.cpp
   src/String/test_indexOf.cpp
   src/String/test_lastIndexOf.cpp
   src/String/test_length.cpp

test/src/String/test_characterAccessFunc.cpp

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2020 Arduino.  All rights reserved.
+ */
+
+/**************************************************************************************
+ * INCLUDE
+ **************************************************************************************/
+
+#include <catch.hpp>
+
+#include <String.h>
+
+/**************************************************************************************
+ * TEST CODE
+ **************************************************************************************/
+
+TEST_CASE ("Testing String::charAt(unsigned int)", "[String-charAt-01]")
+{
+  arduino::String str1("Hello");
+  REQUIRE(str1.charAt(2) == 'l');
+}
+
+TEST_CASE ("Testing String::setCharAt(unsigned int, char )", "[String-setCharAt-02]")
+{
+  arduino::String str1("Hello");
+  str1.setCharAt(1, 'a');
+  REQUIRE(str1.compareTo("Hallo") == 0);
+}
+
+TEST_CASE ("Testing String::getBytes(unsigned char, unsigned int, unsigned int)", "[String-getBytes-02]")
+{
+  WHEN("No bufsize") {
+    arduino::String str("Hello");
+    unsigned char buf[2];
+    str.getBytes(buf, 0, 0);
+  }
+
+  WHEN("Index >= len") {
+    arduino::String str("Hello");
+    unsigned char buf[2];
+    str.getBytes(buf, 5, 6);
+  }
+
+  WHEN("Valid operation") {
+    arduino::String str("Hello");
+    unsigned char buf[2];
+    str.getBytes(buf, 5, 3);
+    REQUIRE(buf[0] == 'l');
+    REQUIRE(buf[1] == 'o');
+  }
+}