From 48b3d82ffe1ed19db9ba3cf7e6536ecf92e27391 Mon Sep 17 00:00:00 2001
From: Szczepan Zalega <szczepan@nitrokey.com>
Date: Fri, 22 Dec 2017 16:53:56 +0100
Subject: Squashed 'unittest/Catch/' content from commit ae5ee2cf

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+# String conversions
+
+Catch needs to be able to convert types you use in assertions and logging expressions into strings (for logging and reporting purposes).
+Most built-in or std types are supported out of the box but there are three ways that you can tell Catch how to convert your own types (or other, third-party types) into strings.
+
+## operator << overload for std::ostream
+
+This is the standard way of providing string conversions in C++ - and the chances are you may already provide this for your own purposes. If you're not familiar with this idiom it involves writing a free function of the form:
+
+```
+std::ostream& operator << ( std::ostream& os, T const& value ) {
+	os << convertMyTypeToString( value );
+	return os;
+}
+```
+
+(where ```T``` is your type and ```convertMyTypeToString``` is where you'll write whatever code is necessary to make your type printable - it doesn't have to be in another function).
+
+You should put this function in the same namespace as your type.
+
+Alternatively you may prefer to write it as a member function:
+
+```
+std::ostream& T::operator << ( std::ostream& os ) const {
+	os << convertMyTypeToString( *this );
+	return os;
+}
+```
+
+## Catch::toString overload
+
+If you don't want to provide an ```operator <<``` overload, or you want to convert your type differently for testing purposes, you can provide an overload for ```Catch::toString()``` for your type.
+
+```
+namespace Catch {
+	std::string toString( T const& value ) {
+		return convertMyTypeToString( value );
+	}
+}
+```
+
+Again ```T``` is your type and ```convertMyTypeToString``` is where you'll write whatever code is necessary to make your type printable. Note that the function must be in the Catch namespace, which itself must be in the global namespace.
+
+## Catch::StringMaker<T> specialisation
+
+There are some cases where overloading toString does not work as expected. Specialising StringMaker<T> gives you more precise, and reliable, control - but at the cost of slightly more code and complexity:
+
+```
+namespace Catch {
+	template<> struct StringMaker<T> {
+    	static std::string convert( T const& value ) {
+        	return convertMyTypeToString( value ); 
+        } 
+    }; 
+}
+```
+
+## Exceptions
+
+By default all exceptions deriving from `std::exception` will be translated to strings by calling the `what()` method. For exception types that do not derive from `std::exception` - or if `what()` does not return a suitable string - use `CATCH_TRANSLATE_EXCEPTION`. This defines a function that takes your exception type, by reference, and returns a string. It can appear anywhere in the code - it doesn't have to be in the same translation unit. For example:
+
+```
+CATCH_TRANSLATE_EXCEPTION( MyType& ex ) {
+	return ex.message();
+}
+```
+
+---
+
+[Home](Readme.md)
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