rework Process API & tests

* Add separate classes ProcessParameters & ShellParameters for
Process::create() and Process::shell() methods.
* Add a separate "worker" executable. It's used in tests via a fairly
complicated scheme, receiving orders to execute via a shared memory
region.
* Add tests that utilize the Console API, reading console window's
screen buffer directly, making for more reliable tests & broader
coverage.

11 files changed, 946 insertions, 11 deletions

diff --git a/test/unit_tests/CMakeLists.txt b/test/unit_tests/CMakeLists.txt
index fb87230..7311d75 100644
--- a/test/unit_tests/CMakeLists.txt
+++ b/test/unit_tests/CMakeLists.txt
@@ -1,5 +1,7 @@
+file(GLOB shared_src "shared/*.hpp")
+
 file(GLOB unit_tests_src "*.cpp" "*.h" "*.hpp" "*.rc")
-add_executable(unit_tests ${unit_tests_src})
+add_executable(unit_tests ${unit_tests_src} ${shared_src})
 set_target_properties(unit_tests PROPERTIES OUTPUT_NAME winapi-common-unit-tests)
 
 target_link_libraries(unit_tests PRIVATE winapi_common winapi_utf8)
@@ -11,3 +13,17 @@ install(TARGETS unit_tests RUNTIME DESTINATION bin)
 if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     install(FILES "$<TARGET_PDB_FILE:unit_tests>" DESTINATION bin OPTIONAL)
 endif()
+
+file(GLOB worker_src "worker/*.cpp")
+add_executable(worker ${worker_src} ${shared_src})
+set_target_properties(worker PROPERTIES OUTPUT_NAME winapi-common-test-worker)
+
+target_link_libraries(worker PRIVATE winapi_common winapi_utf8)
+
+find_package(Boost REQUIRED)
+target_link_libraries(worker PRIVATE Boost::disable_autolinking Boost::boost)
+
+install(TARGETS worker RUNTIME DESTINATION bin)
+if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+    install(FILES "$<TARGET_PDB_FILE:worker>" DESTINATION bin OPTIONAL)
+endif()
diff --git a/test/unit_tests/console.cpp b/test/unit_tests/console.cpp
new file mode 100644
index 0000000..9eb787c
--- /dev/null
+++ b/test/unit_tests/console.cpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#include "shared/console.hpp"
+
+#include <boost/test/unit_test.hpp>
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+BOOST_AUTO_TEST_SUITE(console_tests)
+
+BOOST_AUTO_TEST_CASE(read_last_lines) {
+    std::cout << "abc\ndef" << std::endl;
+    console::Buffer buffer;
+    const auto last = buffer.read_last_line();
+    const auto last2 = buffer.read_last_lines(2);
+    const std::string expected{"def"};
+    const std::vector<std::string> expected2{"abc", "def"};
+    BOOST_TEST(last == expected);
+    BOOST_TEST(last2 == expected2);
+}
+
+BOOST_AUTO_TEST_CASE(read_last_lines_overflow) {
+    console::Buffer buffer;
+    const std::string output(buffer.get_columns() + 5, 'X');
+    std::cout << output << std::endl;
+    buffer.update();
+    const auto last = buffer.read_last_lines(1);
+    const auto last2 = buffer.read_last_lines(2);
+    const std::vector<std::string> expected{"XXXXX"};
+    const std::vector<std::string> expected2{std::string(buffer.get_columns(), 'X'), "XXXXX"};
+    BOOST_TEST(last == expected);
+    BOOST_TEST(last2 == expected2);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/test/unit_tests/fixtures.hpp b/test/unit_tests/fixtures.hpp
index 293ad35..aaf6571 100644
--- a/test/unit_tests/fixtures.hpp
+++ b/test/unit_tests/fixtures.hpp
@@ -5,6 +5,8 @@
 
 #pragma once
 
+#include "shared/command.hpp"
+
 #include <winapi/cmd_line.hpp>
 #include <winapi/file.hpp>
 #include <winapi/path.hpp>
@@ -34,18 +36,13 @@ private:
     RemoveFileGuard& operator=(const RemoveFileGuard&) = delete;
 };
 
-class WithEchoExe {
+class WithParam {
 public:
-    WithEchoExe() : m_echo_exe(find_echo_exe()) {}
+    WithParam(const std::string& param_prefix) : m_value(find_param_value(param_prefix)) {}
 
-    const std::string& get_echo_exe() { return m_echo_exe; }
+    const std::string& get_value() { return m_value; }
 
 private:
-    static std::string find_echo_exe() {
-        static const std::string prefix{"--echo_exe="};
-        return find_param_value(prefix);
-    }
-
     static std::string find_param_value(const std::string& param_prefix) {
         const auto cmd_line = winapi::CommandLine::query();
         const auto& args = cmd_line.get_args();
@@ -57,5 +54,21 @@ private:
         throw std::runtime_error{"couldn't find parameter " + param_prefix};
     }
 
-    std::string m_echo_exe;
+    std::string m_value;
+};
+
+class WithEchoExe : public WithParam {
+public:
+    WithEchoExe() : WithParam{"--echo_exe="} {}
+
+    const std::string& get_echo_exe() { return get_value(); }
+};
+
+class WithWorkerExe : public WithParam {
+public:
+    WithWorkerExe() : WithParam{"--worker_exe="}, m_cmd{worker::Command::create()} {}
+
+    const std::string& get_worker_exe() { return get_value(); }
+
+    worker::Command::Shared m_cmd;
 };
diff --git a/test/unit_tests/process.cpp b/test/unit_tests/process.cpp
index cfc50f4..a048c84 100644
--- a/test/unit_tests/process.cpp
+++ b/test/unit_tests/process.cpp
@@ -86,7 +86,8 @@ BOOST_FIXTURE_TEST_CASE(echo_stdin_from_file, WithEchoExe) {
 
 BOOST_FIXTURE_TEST_CASE(echo_runas, WithEchoExe) {
     const CommandLine cmd_line{get_echo_exe(), {"foo", "bar"}};
-    const auto process = Process::runas(cmd_line);
+    const auto params = ShellParameters::runas(cmd_line);
+    const auto process = Process::shell(params);
     process.wait();
     BOOST_TEST(process.get_exit_code() == 0);
 }
diff --git a/test/unit_tests/process_worker.cpp b/test/unit_tests/process_worker.cpp
new file mode 100644
index 0000000..492ffff
--- /dev/null
+++ b/test/unit_tests/process_worker.cpp
@@ -0,0 +1,278 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#include "fixtures.hpp"
+#include "shared/command.hpp"
+#include "shared/console.hpp"
+#include "shared/test_data.hpp"
+#include "shared/worker.hpp"
+
+#include <winapi/buffer.hpp>
+#include <winapi/cmd_line.hpp>
+#include <winapi/handle.hpp>
+#include <winapi/pipe.hpp>
+#include <winapi/process.hpp>
+#include <winapi/process_io.hpp>
+
+#include <boost/test/unit_test.hpp>
+
+#include <windows.h>
+
+#include <cstddef>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+using winapi::Buffer;
+using winapi::CommandLine;
+using winapi::Handle;
+using winapi::Pipe;
+using winapi::Process;
+using winapi::ProcessParameters;
+namespace process = winapi::process;
+
+using worker::StdHandles;
+using worker::Worker;
+
+namespace {
+
+void check_window_same(Worker& worker) {
+    BOOST_TEST(::GetConsoleWindow());
+    BOOST_TEST(worker.get_console_window() == ::GetConsoleWindow());
+    BOOST_TEST(worker.is_window_visible());
+}
+
+void check_window_none(Worker& worker) {
+    BOOST_TEST(::GetConsoleWindow());
+    BOOST_TEST(!worker.get_console_window());
+    BOOST_TEST(!worker.is_window_visible());
+}
+
+void check_window_new(Worker& worker) {
+    BOOST_TEST(::GetConsoleWindow());
+    BOOST_TEST(worker.get_console_window());
+    BOOST_TEST(worker.get_console_window() != ::GetConsoleWindow());
+    BOOST_TEST(worker.is_window_visible());
+}
+
+void check_std_handles(Worker& worker, const StdHandles& expected) {
+    const auto actual = worker.get_std_handles();
+    BOOST_TEST(actual.in == expected.in);
+    BOOST_TEST(actual.out == expected.out);
+    BOOST_TEST(actual.err == expected.err);
+}
+
+void check_std_handles_same(Worker& worker) {
+    check_std_handles(worker,
+                      {::GetStdHandle(STD_INPUT_HANDLE),
+                       ::GetStdHandle(STD_OUTPUT_HANDLE),
+                       ::GetStdHandle(STD_ERROR_HANDLE)});
+}
+
+void check_std_handles_different(Worker& worker) {
+    const auto actual = worker.get_std_handles();
+    BOOST_TEST(actual.in);
+    BOOST_TEST(actual.out);
+    BOOST_TEST(actual.err);
+    BOOST_TEST(actual.in != ::GetStdHandle(STD_INPUT_HANDLE));
+    BOOST_TEST(actual.out != ::GetStdHandle(STD_OUTPUT_HANDLE));
+    BOOST_TEST(actual.err != ::GetStdHandle(STD_ERROR_HANDLE));
+}
+
+void check_write(Worker& worker) {
+    const auto handles = worker.test_write();
+    BOOST_TEST(!Handle::is_invalid(handles.in));
+    BOOST_TEST(!Handle::is_invalid(handles.out));
+    BOOST_TEST(!Handle::is_invalid(handles.err));
+}
+
+void check_redirected_output(const Buffer& buffer, const std::vector<std::string>& expected_lines) {
+    const auto actual = buffer.as_utf8();
+    std::ostringstream oss;
+    for (const auto& line : expected_lines) {
+        oss << line << "\r\n";
+    }
+    const std::string expected{oss.str()};
+    BOOST_TEST(actual == expected);
+}
+
+const std::string PLACEHOLDER{"This is a placeholder line."};
+
+void check_console_buffer_inherit(Worker& worker, const std::vector<std::string>& expected) {
+    // Check that
+    // 1) the worker process writes the expected lines to its console window,
+    // 2) the lines appear in this process's window, since they're the same.
+
+    const auto numof_lines = expected.size();
+    // Write some lines in this process's window, they should be overwritten
+    // by worker's writes.
+    for (std::size_t i = 0; i < numof_lines; ++i) {
+        std::cout << PLACEHOLDER << std::endl;
+    }
+    // Order worker to write the lines:
+    const auto handles = worker.test_write();
+    // Query worker process's window:
+    const auto worker_actual = worker.read_last_lines(numof_lines);
+    // Query this process's window:
+    const auto this_actual = console::Buffer{}.read_last_lines(numof_lines);
+
+    // They should look the same:
+    const auto& worker_expected = expected;
+    const auto& this_expected = worker_expected;
+
+    BOOST_TEST(worker_actual == worker_expected);
+    BOOST_TEST(this_actual == this_expected);
+}
+
+void check_console_buffer_new(Worker& worker, const std::vector<std::string>& expected) {
+    // Check that
+    // 1) the worker process writes the expected lines in its console window,
+    // 2) the lines _do not_ appear in this process's window, since they're
+    // different windows.
+
+    const auto numof_lines = expected.size();
+    // Write some lines in this process's window, they _should not_ be
+    // overwritten by worker's writes.
+    for (std::size_t i = 0; i < numof_lines; ++i) {
+        std::cout << PLACEHOLDER << std::endl;
+    }
+    // Order worker to write the lines:
+    const auto handles = worker.test_write();
+    // Query worker process's window:
+    const auto worker_actual = worker.read_last_lines(numof_lines);
+    // Query this process's window:
+    const auto this_actual = console::Buffer{}.read_last_lines(numof_lines);
+
+    // Placeholder lines are still last in this process's window:
+    const auto& worker_expected = expected;
+    const std::vector<std::string> this_expected(numof_lines, PLACEHOLDER);
+
+    BOOST_TEST(worker_actual == worker_expected);
+    BOOST_TEST(this_actual == this_expected);
+}
+
+// CREATE_NO_WINDOW actually does create a new buffer, it's just invisible.
+void check_console_buffer_none(Worker& worker, const std::vector<std::string>& expected) {
+    check_console_buffer_new(worker, expected);
+}
+
+} // namespace
+
+BOOST_AUTO_TEST_SUITE(process_console_tests)
+
+BOOST_FIXTURE_TEST_CASE(create_inherit, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleInherit;
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_same(worker);
+    check_std_handles_same(worker);
+    check_write(worker);
+    check_console_buffer_inherit(worker, {worker::test_data::out(), worker::test_data::err()});
+    BOOST_TEST(worker.exit() == 0);
+}
+
+BOOST_FIXTURE_TEST_CASE(create_inherit_override, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleInherit;
+
+    Pipe stdin_pipe, stderr_pipe;
+    const StdHandles expected_handles{
+        stdin_pipe.read_end().get(), Handle::std_out().get(), stderr_pipe.write_end().get()};
+
+    process::IO io;
+    io.std_in = process::Stdin{stdin_pipe};
+    io.std_err = process::Stderr{stderr_pipe};
+    params.io = std::move(io);
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_same(worker);
+    check_std_handles(worker, expected_handles);
+    check_write(worker);
+    check_console_buffer_inherit(worker, {worker::test_data::out()});
+    BOOST_TEST(worker.exit() == 0);
+    check_redirected_output(stderr_pipe.read_end().read(),
+                            {worker::test_data::err(), worker::test_data::err()});
+}
+
+BOOST_FIXTURE_TEST_CASE(create_none, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleNone;
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_none(worker);
+    check_std_handles_different(worker);
+    check_write(worker);
+    check_console_buffer_none(worker, {worker::test_data::out(), worker::test_data::err()});
+    BOOST_TEST(worker.exit() == 0);
+}
+
+BOOST_FIXTURE_TEST_CASE(create_none_override, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleNone;
+
+    Pipe stdin_pipe, stderr_pipe;
+    const StdHandles expected_handles{
+        stdin_pipe.read_end().get(), Handle::std_out().get(), stderr_pipe.write_end().get()};
+
+    process::IO io;
+    io.std_in = process::Stdin{stdin_pipe};
+    io.std_err = process::Stderr{stderr_pipe};
+    params.io = std::move(io);
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_none(worker);
+    check_std_handles(worker, expected_handles);
+    check_write(worker);
+    check_console_buffer_none(worker, {worker::test_data::out()});
+    BOOST_TEST(worker.exit() == 0);
+    check_redirected_output(stderr_pipe.read_end().read(),
+                            {worker::test_data::err(), worker::test_data::err()});
+}
+
+BOOST_FIXTURE_TEST_CASE(create_new, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleNew;
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_new(worker);
+    check_std_handles_different(worker);
+    check_write(worker);
+    check_console_buffer_new(worker, {worker::test_data::out(), worker::test_data::err()});
+    BOOST_TEST(worker.exit() == 0);
+}
+
+BOOST_FIXTURE_TEST_CASE(create_new_override, WithWorkerExe) {
+    const CommandLine cmd_line{get_worker_exe()};
+    ProcessParameters params{cmd_line};
+    params.console_mode = ProcessParameters::ConsoleNew;
+
+    Pipe stdin_pipe, stderr_pipe;
+    const StdHandles expected_handles{
+        stdin_pipe.read_end().get(), Handle::std_out().get(), stderr_pipe.write_end().get()};
+
+    process::IO io;
+    io.std_in = process::Stdin{stdin_pipe};
+    io.std_err = process::Stderr{stderr_pipe};
+    params.io = std::move(io);
+
+    Worker worker{Process::create(std::move(params))};
+    check_window_new(worker);
+    check_std_handles(worker, expected_handles);
+    check_write(worker);
+    check_console_buffer_new(worker, {worker::test_data::out()});
+    BOOST_TEST(worker.exit() == 0);
+    check_redirected_output(stderr_pipe.read_end().read(),
+                            {worker::test_data::err(), worker::test_data::err()});
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/test/unit_tests/shared/command.hpp b/test/unit_tests/shared/command.hpp
new file mode 100644
index 0000000..de7c704
--- /dev/null
+++ b/test/unit_tests/shared/command.hpp
@@ -0,0 +1,142 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include "fixed_size.hpp"
+
+#include <winapi/shmem.hpp>
+
+#include <boost/config.hpp>
+#include <boost/interprocess/sync/interprocess_condition.hpp>
+#include <boost/interprocess/sync/interprocess_mutex.hpp>
+#include <boost/interprocess/sync/scoped_lock.hpp>
+
+#include <windows.h>
+
+#include <cstddef>
+#include <exception>
+#include <functional>
+#include <stdexcept>
+
+namespace worker {
+
+struct StdHandles {
+    HANDLE in;
+    HANDLE out;
+    HANDLE err;
+};
+
+class Command {
+public:
+    BOOST_STATIC_CONSTEXPR auto SHMEM_NAME = "shmem-test-cmd";
+
+    typedef winapi::SharedObject<Command> Shared;
+
+    static Shared create() { return Shared::create(SHMEM_NAME); }
+    static Shared open() { return Shared::open(SHMEM_NAME); }
+
+    typedef boost::interprocess::interprocess_mutex mutex;
+    typedef boost::interprocess::interprocess_condition condition_variable;
+    typedef boost::interprocess::scoped_lock<mutex> lock;
+
+    enum Action {
+        EXIT = 1,
+        GET_CONSOLE_WINDOW,
+        IS_WINDOW_VISIBLE,
+        GET_STD_HANDLES,
+        TEST_WRITE,
+        GET_CONSOLE_BUFFER,
+    };
+
+    union Args {
+        std::size_t numof_lines;
+    };
+
+    union Result {
+        HWND console_window;
+        bool is_window_visible;
+        StdHandles std_handles;
+        fixed_size::StringList<> console_buffer;
+    };
+
+    typedef std::function<void(Args&)> SetArgs;
+    typedef std::function<void(const Result&)> ReadResult;
+
+    void get_result(Action action, const SetArgs& set_args, const ReadResult& read_result) {
+        {
+            lock lck{m_mtx};
+            m_action = action;
+            set_args(m_args);
+
+            m_action_requested = true;
+            m_result_ready = false;
+            m_error_occured = false;
+        }
+        m_cv.notify_all();
+
+        lock lck{m_mtx};
+        m_cv.wait(lck, [this]() { return m_error_occured || m_result_ready; });
+
+        const auto error = m_error_occured;
+
+        m_action_requested = false;
+        m_result_ready = false;
+        m_error_occured = false;
+
+        if (error) {
+            throw std::runtime_error{"Worker error: " + m_error.extract()};
+        }
+
+        read_result(m_result);
+    }
+
+    void get_result(Action action, const ReadResult& read_result) {
+        return get_result(
+            action, [](Args&) {}, read_result);
+    }
+
+    void get_result(Action action) {
+        return get_result(action, [](const Result&) {});
+    }
+
+    typedef std::function<void(Action, const Args&, Result&)> ProcessAction;
+
+    void process_action(const ProcessAction& callback) {
+        {
+            lock lck{m_mtx};
+            m_cv.wait(lck, [this]() { return m_action_requested; });
+
+            m_action_requested = false;
+            m_result_ready = false;
+            m_error_occured = false;
+
+            try {
+                callback(m_action, m_args, m_result);
+                m_result_ready = true;
+            } catch (const std::exception& e) {
+                m_error_occured = true;
+                m_error = m_error.convert(e.what());
+            }
+        }
+        m_cv.notify_all();
+    }
+
+private:
+    Action m_action;
+    Args m_args;
+    bool m_action_requested = false;
+
+    Result m_result;
+    bool m_result_ready = false;
+
+    bool m_error_occured = false;
+    fixed_size::String<> m_error;
+
+    mutex m_mtx;
+    condition_variable m_cv;
+};
+
+} // namespace worker
diff --git a/test/unit_tests/shared/console.hpp b/test/unit_tests/shared/console.hpp
new file mode 100644
index 0000000..0a415e5
--- /dev/null
+++ b/test/unit_tests/shared/console.hpp
@@ -0,0 +1,138 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include <winapi/error.hpp>
+#include <winapi/handle.hpp>
+#include <winapi/utf8.hpp>
+
+#include <boost/algorithm/string.hpp>
+
+#include <windows.h>
+
+#include <cstddef>
+#include <cstring>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace console {
+
+class Buffer {
+public:
+    typedef CONSOLE_SCREEN_BUFFER_INFO Info;
+
+    Buffer() : m_handle{winapi::Handle::std_out()}, m_info{get_info(m_handle)} {}
+
+    Buffer(winapi::Handle&& handle) : m_handle{std::move(handle)}, m_info{get_info(m_handle)} {}
+
+    std::size_t get_columns() const { return m_info.dwSize.X; }
+
+    std::size_t get_lines() const { return m_info.dwSize.Y; }
+
+    std::size_t get_cursor_column() const { return m_info.dwCursorPosition.X; }
+
+    std::size_t get_cursor_line() const { return m_info.dwCursorPosition.Y; }
+
+    void update() { m_info = get_info(m_handle); }
+
+    /*
+     * This is a stupid little function to read the console screen buffer.
+     * It's fragile and will break whenever anything happens (like, if the
+     * console screen is resized).
+     *
+     * The screen buffer:
+     * 1) doesn't preserve line breaks,
+     * 2) pads text lines with spaces (ASCII 0x20) for storage.
+     *
+     * Hence, the "lines" read are one-dimensional arrays, right-trimmed, and
+     * there's no way to learn whether the whole line printed by the user was
+     * read back in its entirety.
+     *
+     * For example, let the console window be 80 columns wide, and the user
+     * prints 85 consecutive characters 'a' using
+     *
+     *     std::cout << std::string(85, 'a') << '\n';
+     *
+     * The following holds:
+     * 1) read_lines(-1, -1) == {"aaaaa"},
+     * 2) read_lines(-2, -2) == {std::string(80, 'a'), "aaaaa"}.
+     *
+     * I also don't know how it interacts with tab characters '\t', encodings,
+     * etc. It sucks, don't use it.
+     */
+    std::vector<std::string> read_lines(int top, int bottom) const {
+        if (top < 0) {
+            top = get_cursor_line() + top;
+        }
+        if (bottom < 0) {
+            bottom = get_cursor_line() + bottom;
+        }
+        if (top > bottom) {
+            std::swap(top, bottom);
+        }
+        int numof_lines = bottom - top + 1;
+
+        COORD buffer_size;
+        buffer_size.X = get_columns();
+        buffer_size.Y = numof_lines;
+
+        COORD buffer_coord;
+        buffer_coord.X = 0;
+        buffer_coord.Y = 0;
+
+        std::vector<CHAR_INFO> buffer;
+        buffer.resize(buffer_size.X * buffer_size.Y);
+
+        SMALL_RECT read_region;
+        read_region.Top = top;
+        read_region.Left = 0;
+        read_region.Bottom = bottom;
+        read_region.Right = buffer_size.X - 1;
+
+        if (!::ReadConsoleOutputW(
+                m_handle.get(), buffer.data(), buffer_size, buffer_coord, &read_region)) {
+            throw winapi::error::windows(GetLastError(), "ReadConsoleOutputW");
+        }
+
+        std::vector<std::string> result;
+        for (std::size_t i = 0; i < numof_lines; ++i) {
+            std::wostringstream oss;
+            for (std::size_t c = 0; c < buffer_size.X; ++c) {
+                oss << buffer[i * buffer_size.X + c].Char.UnicodeChar;
+            }
+            result.emplace_back(boost::trim_right_copy(winapi::narrow(oss.str())));
+        }
+
+        return result;
+    }
+
+    std::vector<std::string> read_last_lines(int numof_lines = 1) const {
+        return read_lines(-numof_lines, -1);
+    }
+
+    std::string read_last_line() const { return read_lines(-1, -1)[0]; }
+
+    std::string read_line(int n) const { return read_lines(n, n)[0]; }
+
+private:
+    static Info get_info(const winapi::Handle& handle) {
+        Info dest;
+        std::memset(&dest, 0, sizeof(dest));
+
+        if (!::GetConsoleScreenBufferInfo(static_cast<HANDLE>(handle), &dest)) {
+            throw winapi::error::windows(GetLastError(), "GetConsoleScreenBufferInfo");
+        }
+
+        return dest;
+    }
+
+    winapi::Handle m_handle;
+    Info m_info;
+};
+
+} // namespace console
diff --git a/test/unit_tests/shared/fixed_size.hpp b/test/unit_tests/shared/fixed_size.hpp
new file mode 100644
index 0000000..e4b11c7
--- /dev/null
+++ b/test/unit_tests/shared/fixed_size.hpp
@@ -0,0 +1,79 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include <array>
+#include <cstddef>
+#include <cstring>
+#include <string>
+#include <vector>
+
+namespace fixed_size {
+
+/*
+ * These are fixed-size classes, to be used as part of an interprocess shared
+ * memory region.
+ */
+
+// 120 characters is an arbitrary limit, strings are cut to this many
+// characters for storage.
+template <std::size_t Length = 120>
+class String : public std::array<char, Length> {
+public:
+    static String convert(const std::string& src) {
+        String dest;
+        std::size_t nch = dest.size() - 1;
+        if (src.size() < nch) {
+            nch = src.size();
+        }
+        std::memcpy(dest.data(), src.c_str(), nch);
+        dest[nch] = '\0';
+        return dest;
+    }
+
+    std::string extract() const {
+        // Lines are null-terminated, and don't store their lenghts, so...
+        return data();
+    }
+
+private:
+};
+
+// 5 lines to store is also arbitrary, set it higher if needed.
+template <std::size_t Length = 5, std::size_t StringLength = 120>
+struct StringList : public std::array<String<StringLength>, Length> {
+    static StringList convert(const std::vector<std::string>& src) {
+        // If src.size() > Length, only the last Length lines from the source
+        // list are stored.
+
+        StringList dest;
+        std::memset(&dest, 0, sizeof(dest));
+
+        std::size_t src_offset = 0;
+        if (src.size() > dest.size()) {
+            src_offset = src.size() - dest.size();
+        }
+
+        for (std::size_t i = 0, j = src_offset; i < dest.size() && j < src.size();
+             ++i, ++j, ++dest.numof_lines) {
+            dest[i] = dest[i].convert(src[j]);
+        }
+
+        return dest;
+    }
+
+    std::vector<std::string> extract() const {
+        std::vector<std::string> dest;
+        for (std::size_t i = 0; i < numof_lines; ++i) {
+            dest.emplace_back(at(i).extract());
+        }
+        return dest;
+    }
+
+    std::size_t numof_lines;
+};
+
+} // namespace fixed_size
diff --git a/test/unit_tests/shared/test_data.hpp b/test/unit_tests/shared/test_data.hpp
new file mode 100644
index 0000000..0094f0b
--- /dev/null
+++ b/test/unit_tests/shared/test_data.hpp
@@ -0,0 +1,24 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include <string>
+
+namespace worker {
+namespace test_data {
+
+BOOST_STATIC_CONSTEXPR auto str = "Test output.";
+
+inline std::string out() {
+    return "stdout: " + std::string{str};
+}
+
+inline std::string err() {
+    return "stderr: " + std::string{str};
+}
+
+} // namespace test_data
+} // namespace worker
diff --git a/test/unit_tests/shared/worker.hpp b/test/unit_tests/shared/worker.hpp
new file mode 100644
index 0000000..320a924
--- /dev/null
+++ b/test/unit_tests/shared/worker.hpp
@@ -0,0 +1,86 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include "command.hpp"
+
+#include <winapi/process.hpp>
+
+#include <windows.h>
+
+#include <exception>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace worker {
+
+class Worker {
+public:
+    Worker(winapi::Process&& process) : m_cmd{Command::create()}, m_process{std::move(process)} {}
+
+    ~Worker() {
+        try {
+            if (m_process.is_running()) {
+                exit();
+            }
+        } catch (const std::exception&) {
+        }
+    }
+
+    HWND get_console_window() {
+        HWND ret = NULL;
+        m_cmd->get_result(Command::GET_CONSOLE_WINDOW,
+                          [&ret](const Command::Result& result) { ret = result.console_window; });
+        return ret;
+    }
+
+    bool is_window_visible() {
+        bool ret = false;
+        m_cmd->get_result(Command::IS_WINDOW_VISIBLE, [&ret](const Command::Result& result) {
+            ret = result.is_window_visible;
+        });
+        return ret;
+    }
+
+    StdHandles get_std_handles() {
+        StdHandles ret;
+        m_cmd->get_result(Command::GET_STD_HANDLES,
+                          [&ret](const Command::Result& result) { ret = result.std_handles; });
+        return ret;
+    }
+
+    StdHandles test_write() {
+        StdHandles ret;
+        m_cmd->get_result(Command::TEST_WRITE,
+                          [&ret](const Command::Result& result) { ret = result.std_handles; });
+        return ret;
+    }
+
+    std::vector<std::string> read_last_lines(std::size_t numof_lines) {
+        std::vector<std::string> ret;
+        const auto set_args = [numof_lines](Command::Args& args) {
+            args.numof_lines = numof_lines;
+        };
+        const auto read_result = [&ret](const Command::Result& result) {
+            ret = result.console_buffer.extract();
+        };
+        m_cmd->get_result(Command::GET_CONSOLE_BUFFER, set_args, read_result);
+        return ret;
+    }
+
+    int exit() {
+        m_cmd->get_result(Command::EXIT);
+        m_process.wait();
+        return m_process.get_exit_code();
+    }
+
+private:
+    Command::Shared m_cmd;
+    winapi::Process m_process;
+};
+
+} // namespace worker
diff --git a/test/unit_tests/worker/worker.cpp b/test/unit_tests/worker/worker.cpp
new file mode 100644
index 0000000..9e48deb
--- /dev/null
+++ b/test/unit_tests/worker/worker.cpp
@@ -0,0 +1,118 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#include "../shared/command.hpp"
+#include "../shared/console.hpp"
+#include "../shared/test_data.hpp"
+
+#include <winapi/error.hpp>
+#include <winapi/handle.hpp>
+
+#include <windows.h>
+
+#include <chrono>
+#include <cstddef>
+#include <exception>
+#include <stdexcept>
+#include <string>
+#include <thread>
+#include <vector>
+
+using worker::Command;
+
+namespace {
+
+bool is_window_visible() {
+    HWND window = ::GetConsoleWindow();
+
+    if (window == NULL) {
+        return false;
+    }
+
+    const auto mask = ::GetWindowLongW(window, GWL_STYLE);
+
+    if (!mask) {
+        throw winapi::error::windows(GetLastError(), "GetWindowLongW");
+    }
+
+    return mask & WS_VISIBLE;
+}
+
+winapi::Handle write_to(winapi::Handle dest, const std::string& msg) {
+    try {
+        dest.write(msg + "\r\n");
+    } catch (const std::exception& e) {
+        return winapi::Handle{};
+    }
+    return dest;
+}
+
+std::vector<std::string> get_console_buffer(std::size_t numof_lines) {
+    return console::Buffer{}.read_last_lines(numof_lines);
+}
+
+void process_action(Command::Action action, const Command::Args& args, Command::Result& result) {
+    switch (action) {
+        case Command::EXIT:
+            break;
+
+        case Command::GET_CONSOLE_WINDOW:
+            result.console_window = ::GetConsoleWindow();
+            break;
+
+        case Command::IS_WINDOW_VISIBLE:
+            result.is_window_visible = is_window_visible();
+            break;
+
+        case Command::GET_STD_HANDLES:
+            result.std_handles.in = ::GetStdHandle(STD_INPUT_HANDLE);
+            result.std_handles.out = ::GetStdHandle(STD_OUTPUT_HANDLE);
+            result.std_handles.err = ::GetStdHandle(STD_ERROR_HANDLE);
+            break;
+
+        case Command::TEST_WRITE:
+            result.std_handles.in = winapi::Handle::std_in().get();
+            result.std_handles.out =
+                write_to(winapi::Handle::std_out(), worker::test_data::out()).get();
+            result.std_handles.err =
+                write_to(winapi::Handle::std_err(), worker::test_data::err()).get();
+            break;
+
+        case Command::GET_CONSOLE_BUFFER:
+            result.console_buffer =
+                result.console_buffer.convert(get_console_buffer(args.numof_lines));
+            break;
+
+        default:
+            throw std::runtime_error{"invalid worker command"};
+    }
+}
+
+int loop() {
+    auto exit_loop = false;
+
+    const auto cmd = Command::open();
+
+    while (!exit_loop) {
+        cmd->process_action([&exit_loop](Command::Action action,
+                                         const Command::Args& args,
+                                         Command::Result& result) {
+            if (action == Command::EXIT) {
+                exit_loop = true;
+            } else {
+                process_action(action, args, result);
+            }
+        });
+    }
+    return 0;
+}
+
+} // namespace
+
+int main(int argc, char* argv[]) {
+    int ec = loop();
+    std::this_thread::sleep_for(std::chrono::milliseconds{1000});
+    return ec;
+}