Update logic to capture stderr

Author: tharun571

test/test_interpreter.cpp

@@ -26,23 +26,24 @@
 #endif
 
 // Object for capturing stderr
-class StdErrRedirect {
-public:
-    StdErrRedirect(std::ostream& new_stream) : old_cerr_buff(std::cerr.rdbuf()), ss(static_cast<std::stringstream&>(new_stream)) {
-        std::cerr.rdbuf(ss.rdbuf());
-    }
+class StreamRedirectRAII {
+    public:
+        StreamRedirectRAII(std::ostream& stream) : old_stream_buff(stream.rdbuf()), stream_to_redirect(stream) {
+            stream_to_redirect.rdbuf(ss.rdbuf());
+        }
 
-    ~StdErrRedirect() {
-        std::cerr.rdbuf(old_cerr_buff);
-    }
+        ~StreamRedirectRAII() {
+            stream_to_redirect.rdbuf(old_stream_buff);
+        }
 
-    std::string getCaptured() {
-        return ss.str();
-    }
+        std::string getCaptured() {
+            return ss.str();
+        }
 
-private:
-    std::streambuf* old_cerr_buff;
-    std::stringstream& ss;
+    private:
+        std::streambuf* old_stream_buff;
+        std::ostream& stream_to_redirect;
+        std::stringstream ss;
 };
 
 TEST_SUITE("execute_request")
@@ -694,16 +695,15 @@ TEST_SUITE("xmagics_apply"){
     } 
 
     TEST_CASE("cell magic with empty cell body") {
+        
         xcpp::xmagics_manager manager;
 
-        std::stringstream ss;
-    StdErrRedirect redirect(ss);
-
-    manager.apply("test", "line", "");
+        StreamRedirectRAII redirect(std::cerr);
 
-    REQUIRE(redirect.getCaptured() == "UsageError: %%test is a cell magic, but the cell body is empty.\n"
-                  "If you only intend to display %%test help, please use a double line break to fill in the cell body.\n");
+        manager.apply("test", "line", "");
 
+        REQUIRE(redirect.getCaptured() == "UsageError: %%test is a cell magic, but the cell body is empty.\n"
+                    "If you only intend to display %%test help, please use a double line break to fill in the cell body.\n");
     }
 }