Added a test for += String operator

diff --git a/test/string_cat.cpp b/test/string_cat.cpp
index 6dffb01..56c1da8 100644 (file)
--- a/test/string_cat.cpp
+++ b/test/string_cat.cpp
@@ -25,6 +25,11 @@ int main()
    std::cout << s2 << " + " << s1 << " = " << s4 << "\n";
    assert(s4 == "defabc");
 
+   s3 = s1;
+   s3 += s2;
+   std::cout << s1 << " += " << s2 << " = " << s3 << "\n";
+   assert(s3 == "abcdef");
+
    return 0;
 }