[coll] Add nccl. (#9726)

tests/cpp/collective/test_worker.cuh

@@ -0,0 +1,32 @@
+/**
+ * Copyright 2023, XGBoost Contributors
+ */
+#pragma once
+#include <memory>  // for shared_ptr
+
+#include "../../../src/collective/coll.h"  // for Coll
+#include "../../../src/collective/comm.h"  // for Comm
+#include "test_worker.h"
+#include "xgboost/context.h"  // for Context
+
+namespace xgboost::collective {
+class NCCLWorkerForTest : public WorkerForTest {
+ protected:
+  std::shared_ptr<Coll> coll_;
+  std::shared_ptr<xgboost::collective::Comm> nccl_comm_;
+  std::shared_ptr<Coll> nccl_coll_;
+  Context ctx_;
+
+ public:
+  using WorkerForTest::WorkerForTest;
+
+  void Setup() {
+    ctx_ = MakeCUDACtx(comm_.Rank());
+    coll_.reset(new Coll{});
+    nccl_comm_.reset(this->comm_.MakeCUDAVar(&ctx_, coll_));
+    nccl_coll_.reset(coll_->MakeCUDAVar());
+    ASSERT_EQ(comm_.World(), nccl_comm_->World());
+    ASSERT_EQ(comm_.Rank(), nccl_comm_->Rank());
+  }
+};
+}  // namespace xgboost::collective