As of merging #295 coverage started flaking.
These lines from the test server filter are no longer always covered:

65 | 0 | decoder_callbacks_->sendLocalReply(
66 | 0 | static_cast<Envoy::Http::Code>(500),
67 | 0 | fmt::format("test-server didn't understand the request: {}", *error_message_), nullptr,
68 | 0 | absl::nullopt, "");
69 | 0 | }

Apparently, the default simple warmup we had helped structurally hitting these lines.
It would be good to have an explicit test for this.

(from https://11211-180498819-gh.circle-artifacts.com/0/coverage/coverage/proc/self/cwd/source/server/http_test_server_filter.cc.html#L64)