add tests and examples

untests/defer_examples.cpp

@@ -7,11 +7,53 @@
 #define CATCH_CONFIG_FAST_COMPILE
 #include <catch2/catch.hpp>
 
+#include <iostream>
 #include <defer.hpp/defer.hpp>
 
-namespace
-{
-}
-
 TEST_CASE("examples") {
+    SECTION("basic_defer") {
+        if ( FILE *file = ::fopen("output.txt", "a") ) {
+            // defer will close the file after scope or on exception
+            DEFER([file]{ ::fclose(file); });
+
+            const char buffer[] = "hello world\n";
+            if ( 12 != ::fwrite(buffer, sizeof(buffer[0]), ::strlen(buffer), file) ) {
+                throw std::runtime_error("some exception");
+            }
+        }
+    }
+
+    SECTION("error_defer") {
+        if ( FILE *file = ::fopen("output.txt", "a") ) {
+            // defer will close the file after scope or on exception
+            DEFER([file]{ ::fclose(file); });
+
+            // error defer will be called on exception
+            ERROR_DEFER([]{
+                std::cerr << "there is something wrong" << std::endl;
+            });
+
+            const char buffer[] = "hello world\n";
+            if ( 12 != ::fwrite(buffer, sizeof(buffer[0]), ::strlen(buffer), file) ) {
+                throw std::runtime_error("some exception");
+            }
+        }
+    }
+
+    SECTION("return_defer") {
+        if ( FILE *file = ::fopen("output.txt", "a") ) {
+            // defer will close the file after scope or on exception
+            DEFER([file]{ ::fclose(file); });
+
+            // return defer will be called on successful scope exit
+            RETURN_DEFER([]{
+                std::cout << "all is ok!" << std::endl;
+            });
+
+            const char buffer[] = "hello world\n";
+            if ( 12 != ::fwrite(buffer, sizeof(buffer[0]), ::strlen(buffer), file) ) {
+                throw std::runtime_error("some exception");
+            }
+        }
+    }
 }