STL: suspicious conditions when using find. Added ok testcases and assert that no error message is written

test/teststl.cpp

@@ -646,17 +646,42 @@ private:
 
     void if_find()
     {
+        // ---------------------------
+        // string::find
+        // ---------------------------
+
+        // error
         check("void f(std::string s)\n"
               "{\n"
               "    if (s.find(\"ab\")) { }\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:3]: (possible style) Suspicious condition. string::find will return 0 if the string is found at position 0. If this is what you want to check then string::compare is a faster alternative because it doesn't scan through the string.\n", errout.str());
 
+        // ok
+        check("void f(std::string s)\n"
+              "{\n"
+              "    if (s.find(\"ab\") != std::string::npos) { }\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+
+        // ---------------------------
+        // set::find
+        // ---------------------------
+
+        // error
         check("void f(std::set<int> s)\n"
               "{\n"
               "    if (s.find(12)) { }\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:3]: (style) Suspicious condition. The result of find is an iterator, but it is not properly checked.\n", errout.str());
+
+        // ok
+        check("void f(std::set<int> s)\n"
+              "{\n"
+              "    if (s.find(123) != s.end()) { }\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }