Properly print Arduino String objects in tests

This ensures that checks like:

    REQUIRE(some_str == "ABC");

Actually print the value of some_str instead of just `1` (which is the
String object converted to StringIfHelperType).

This is implemented by adding a specialization of the Catch StringMaker
template, so this only takes effect when StringPrinter.h is included.
This commit includes it in all the String testcases (even ones that do
not strictly use it now) for good measure.

Author: matthijskooijman

Diff for: test/src/String/StringPrinter.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <catch.hpp>
+#include <String.h>
+
+namespace Catch {
+  /**
+   * Template specialization that makes sure Catch can properly print
+   * Arduino Strings when used in comparisons directly.
+   *
+   * Note that without this, String objects are printed as 0 and 1,
+   * because they are implicitly convertible to StringIfHelperType,
+   * which is a dummy pointer.
+   */
+  template<>
+  struct StringMaker<arduino::String> {
+      static std::string convert(const arduino::String& str) {
+	if (str)
+	  return ::Catch::Detail::stringify(std::string(str.c_str(), str.length()));
+	else
+	  return "{invalid String}";
+      }
+  };
+} // namespace Catch

Diff for: test/src/String/test_String.cpp

@@ -12,6 +12,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_characterAccessFunc.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_compareTo.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_comparisonFunc.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_concat.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_indexOf.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_lastIndexOf.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_length.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_operators.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_remove.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_replace.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_substring.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_toDouble.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_toFloat.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_toInt.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_toLowerCase.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_toUpperCase.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/

Diff for: test/src/String/test_trim.cpp

@@ -10,6 +10,8 @@
 
 #include <String.h>
 
+#include "StringPrinter.h"
+
 /**************************************************************************************
  * TEST CODE
  **************************************************************************************/