http2: updates test coverage for Http2CodecImplTest.CheckHeaderValueV…

…alidation (#37966)

The only case where codec behavior differs is `\0`, so that case is
still skipped.

UHV + oghttp2 is also skipped, as otherwise the `compile-time-options`
build fails.

Commit Message:
Additional Description:
Risk Level: none, test only
Testing: ran codec_impl_test locally
Docs Changes:
Release Notes:
Platform Specific Features:

---------

Signed-off-by: Biren Roy <[email protected]>

test/common/http/http2/codec_impl_test.cc

@@ -4448,18 +4448,29 @@ TEST_P(Http2CodecImplTest, CheckHeaderValueValidation) {
   scoped_runtime_.mergeValues({{"envoy.reloadable_features.validate_upstream_headers", "false"}});
   stream_error_on_invalid_http_messaging_ = true;
   initialize();
+
+#ifdef ENVOY_ENABLE_UHV
+  // UHV does not appear to reject some header value chars.
   if (http2_implementation_ == Http2Impl::Oghttp2) {
-    // oghttp2 fails this test for now.
-    return;
+    GTEST_SKIP();
   }
+#endif
 
   // Change one character in the header value and verify that codec correctly
   // accepts or rejects based on the table above.
   std::string header_value{"aaaaaaaa"};
   for (int i = 0; i <= 0xff; ++i) {
+    if (i == 0 && http2_implementation_ == Http2Impl::Oghttp2) {
+      // oghttp2 fails this specific case for now.
+      continue;
+    }
+
     TestRequestHeaderMapImpl request_headers;
     HttpTestUtility::addDefaultHeaders(request_headers);
     header_value[2] = static_cast<char>(i);
+
+    SCOPED_TRACE(absl::StrCat("header value: [", absl::CEscape(header_value), "]"));
+
     HeaderString header_string("a");
     setHeaderStringUnvalidated(header_string, header_value);
     request_headers.addViaMove(HeaderString(absl::string_view("foo")), std::move(header_string));