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diff --git a/src/seastar/tests/unit/mock_file.hh b/src/seastar/tests/unit/mock_file.hh
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+++ b/src/seastar/tests/unit/mock_file.hh
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+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2017 ScyllaDB Ltd.
+ */
+
+#pragma once
+
+#include <boost/range/numeric.hpp>
+
+#include <seastar/testing/seastar_test.hh>
+#include <seastar/core/file.hh>
+
+namespace seastar {
+
+class mock_read_only_file final : public file_impl {
+    bool _closed = false;
+    uint64_t _total_file_size;
+    size_t _allowed_read_requests = 0;
+    std::function<void(size_t)> _verify_length;
+private:
+    size_t verify_read(uint64_t position, size_t length) {
+        BOOST_CHECK(!_closed);
+        BOOST_CHECK_LE(position, _total_file_size);
+        BOOST_CHECK_LE(position + length, _total_file_size);
+        if (position + length != _total_file_size) {
+            _verify_length(length);
+        }
+        BOOST_CHECK(_allowed_read_requests);
+        assert(_allowed_read_requests);
+        _allowed_read_requests--;
+        return length;
+    }
+public:
+    explicit mock_read_only_file(uint64_t file_size) noexcept
+        : _total_file_size(file_size)
+        , _verify_length([] (auto) { })
+    { }
+
+    void set_read_size_verifier(std::function<void(size_t)> fn) {
+        _verify_length = fn;
+    }
+    void set_expected_read_size(size_t expected) {
+        _verify_length = [expected] (auto length) {
+            BOOST_CHECK_EQUAL(length, expected);
+        };
+    }
+    void set_allowed_read_requests(size_t requests) {
+        _allowed_read_requests = requests;
+    }
+
+    virtual future<size_t> write_dma(uint64_t, const void*, size_t, const io_priority_class&) override {
+        throw std::bad_function_call();
+    }
+    virtual future<size_t> write_dma(uint64_t, std::vector<iovec>, const io_priority_class&) override {
+        throw std::bad_function_call();
+    }
+    virtual future<size_t> read_dma(uint64_t pos, void*, size_t len, const io_priority_class&) override {
+        return make_ready_future<size_t>(verify_read(pos, len));
+    }
+    virtual future<size_t> read_dma(uint64_t pos, std::vector<iovec> iov, const io_priority_class&) override {
+        auto length = boost::accumulate(iov | boost::adaptors::transformed([] (auto&& iov) { return iov.iov_len; }),
+                                        size_t(0), std::plus<size_t>());
+        return make_ready_future<size_t>(verify_read(pos, length));
+    }
+    virtual future<> flush() override {
+        return make_ready_future<>();
+    }
+    virtual future<struct stat> stat() override {
+        throw std::bad_function_call();
+    }
+    virtual future<> truncate(uint64_t) {
+        throw std::bad_function_call();
+    }
+    virtual future<> discard(uint64_t offset, uint64_t length) override {
+        throw std::bad_function_call();
+    }
+    virtual future<> allocate(uint64_t position, uint64_t length) override {
+        throw std::bad_function_call();
+    }
+    virtual future<uint64_t> size() override {
+        return make_ready_future<uint64_t>(_total_file_size);
+    }
+    virtual future<> close() override {
+        BOOST_CHECK(!_closed);
+        _closed = true;
+        return make_ready_future<>();
+    }
+    virtual subscription<directory_entry> list_directory(std::function<future<> (directory_entry de)>) override {
+        throw std::bad_function_call();
+    }
+    virtual future<temporary_buffer<uint8_t>> dma_read_bulk(uint64_t offset, size_t range_size, const io_priority_class&) override {
+        auto length = verify_read(offset, range_size);
+        return make_ready_future<temporary_buffer<uint8_t>>(temporary_buffer<uint8_t>(length));
+    }
+};
+
+}