Add test witnessing unescaping bug

src/test.cpp

@@ -3,6 +3,7 @@
 #include <cstdio>
 #include <cstring>
 
+#include <limits>
 #include <string>
 
 #include <doctest.h>
@@ -208,10 +209,10 @@ TEST_CASE("parser3") {
 TEST_CASE("streaming") { testStreaming(json); }
 
 void doTestUnescapingUtf8(std::string const &escaped,
-                          std::string const &expected, bool streaming) {
+                          std::string const &expected, int stride) {
   CAPTURE(escaped);
   CAPTURE(expected);
-  CAPTURE(streaming);
+  CAPTURE(stride);
   auto c = noopCallbacks();
   std::string result;
   c.on_string_data = +[](void *p, const char *buf, int len) {
@@ -220,13 +221,11 @@ void doTestUnescapingUtf8(std::string const &escaped,
   };
   parser3::Parser3 parser(&c, &result);
   auto copy = escaped;
-  if (streaming) {
-    for (int i = 0; i < copy.size(); ++i) {
+  for (int i = 0; i < copy.size(); i += stride) {
     CAPTURE(i);
-      CHECK(parser.parse(copy.data() + i, 1) == parser3::S_AGAIN);
-    }
-  } else {
-    CHECK(parser.parse(copy.data(), copy.size()) == parser3::S_AGAIN);
+    CHECK(
+        parser.parse(copy.data() + i, std::min<int>(stride, copy.size() - i)) ==
+        parser3::S_AGAIN);
   }
   CHECK(parser.parse(nullptr, 0) == parser3::S_OK);
   CHECK(result.size() == expected.size());
@@ -235,8 +234,11 @@ void doTestUnescapingUtf8(std::string const &escaped,
 
 void testUnescapingUtf8(std::string const &escaped,
                         std::string const &expected) {
-  doTestUnescapingUtf8(escaped, expected, false);
-  doTestUnescapingUtf8(escaped, expected, true);
+  for (int stride = 0; stride < 10; ++stride) {
+    doTestUnescapingUtf8(escaped, expected,
+                         stride == 0 ? std::numeric_limits<int>::max()
+                                     : stride);
+  }
 }
 
 TEST_CASE("unescaping utf-8") {