Allow getting consumer group information

tests/test_utils.cpp

@@ -0,0 +1,77 @@
+#include <mutex>
+#include <chrono>
+#include <condition_variable>
+#include "test_utils.h"
+
+using std::vector;
+using std::move;
+using std::thread;
+using std::mutex;
+using std::lock_guard;
+using std::unique_lock;
+using std::condition_variable;
+
+using std::chrono::system_clock;
+using std::chrono::milliseconds;
+using std::chrono::seconds;
+
+using cppkafka::Consumer;
+using cppkafka::Message;
+
+ConsumerRunner::ConsumerRunner(Consumer& consumer, size_t expected, size_t partitions) 
+: consumer_(consumer) {
+    bool booted = false;
+    mutex mtx;
+    condition_variable cond;
+    thread_ = thread([&, expected, partitions]() {
+        consumer_.set_timeout(milliseconds(500));
+        size_t number_eofs = 0;
+        auto start = system_clock::now();
+        while (system_clock::now() - start < seconds(20)) {
+            if (expected > 0 && messages_.size() == expected) {
+                break;
+            }
+            if (expected == 0 && number_eofs >= partitions) {
+                break;
+            }
+            Message msg = consumer_.poll();
+            if (msg && number_eofs != partitions &&
+                msg.get_error() == RD_KAFKA_RESP_ERR__PARTITION_EOF) {
+                number_eofs++;
+                if (number_eofs == partitions) {
+                    lock_guard<mutex> _(mtx);
+                    booted = true;
+                    cond.notify_one();
+                }
+            }
+            else if (msg && !msg.get_error() && number_eofs == partitions) {
+                messages_.push_back(move(msg));
+            }
+        }
+        if (number_eofs < partitions) {
+            lock_guard<mutex> _(mtx);
+            booted = true;
+            cond.notify_one();
+        }
+    });
+
+    unique_lock<mutex> lock(mtx);
+    while (!booted) {
+        cond.wait(lock);
+    }
+}
+
+ConsumerRunner::~ConsumerRunner() {
+    try_join();
+}
+
+const vector<Message>& ConsumerRunner::get_messages() const {
+    return messages_;
+}
+
+void ConsumerRunner::try_join() {
+    if (thread_.joinable()) {
+        thread_.join();
+    }
+}
+