Clean up cmake script and code includes (#106)

* Clean up CMake scripts and related include paths.
* Add unittests.

test/cpp/CMakeLists.txt

@@ -0,0 +1,28 @@
+find_package(GTest REQUIRED)
+
+add_executable(
+  unit_tests
+  allreduce_base_test.cpp
+  test_main.cpp)
+
+target_link_libraries(
+  unit_tests
+  GTest::GTest GTest::Main
+  rabit_base)
+
+target_include_directories(unit_tests PUBLIC
+  "$<BUILD_INTERFACE:${rabit_SOURCE_DIR}/include>"
+  "$<BUILD_INTERFACE:${DMLC_ROOT}/include>")
+
+set_target_properties(unit_tests
+  PROPERTIES
+  CXX_STANDARD 11
+  CXX_STANDARD_REQUIRED ON
+  RUNTIME_OUTPUT_DIRECTORY ${rabit_BINARY_DIR}
+  RUNTIME_OUTPUT_DIRECTORY_DEBUG ${rabit_BINARY_DIR}
+  RUNTIME_OUTPUT_DIRECTORY_RELEASE ${rabit_BINARY_DIR})
+
+add_test(
+  NAME TestRabitLib
+  COMMAND unit_tests
+  WORKING_DIRECTORY ${rabit_BINARY_DIR})

test/cpp/README.md

@@ -0,0 +1 @@
+Unittests for Rabit

test/cpp/allreduce_base_test.cpp

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+#define RABIT_CXXTESTDEFS_H
+#include <gtest/gtest.h>
+
+#include <string>
+#include <iostream>
+#include "../../src/allreduce_base.h"
+
+TEST(allreduce_base, init_task)
+{
+  rabit::engine::AllreduceBase base;
+
+  std::string rabit_task_id = "rabit_task_id=1";
+  char cmd[rabit_task_id.size()+1];
+  std::copy(rabit_task_id.begin(), rabit_task_id.end(), cmd);
+  cmd[rabit_task_id.size()] = '\0';
+
+  char* argv[] = {cmd};
+  base.Init(1, argv);
+  EXPECT_EQ(base.task_id, "1");
+}
+
+TEST(allreduce_base, init_with_cache_on)
+{
+  rabit::engine::AllreduceBase base;
+
+  std::string rabit_task_id = "rabit_task_id=1";
+  char cmd[rabit_task_id.size()+1];
+  std::copy(rabit_task_id.begin(), rabit_task_id.end(), cmd);
+  cmd[rabit_task_id.size()] = '\0';
+
+  std::string rabit_bootstrap_cache = "rabit_bootstrap_cache=1";
+  char cmd2[rabit_bootstrap_cache.size()+1];
+  std::copy(rabit_bootstrap_cache.begin(), rabit_bootstrap_cache.end(), cmd2);
+  cmd2[rabit_bootstrap_cache.size()] = '\0';
+
+  std::string rabit_debug = "rabit_debug=1";
+  char cmd3[rabit_debug.size()+1];
+  std::copy(rabit_debug.begin(), rabit_debug.end(), cmd3);
+  cmd3[rabit_debug.size()] = '\0';
+
+  char* argv[] = {cmd, cmd2, cmd3};
+  base.Init(3, argv);
+  EXPECT_EQ(base.task_id, "1");
+  EXPECT_EQ(base.rabit_bootstrap_cache, 1);
+  EXPECT_EQ(base.rabit_debug, 1);
+}
+
+TEST(allreduce_base, init_with_ring_reduce)
+{
+  rabit::engine::AllreduceBase base;
+
+  std::string rabit_task_id = "rabit_task_id=1";
+  char cmd[rabit_task_id.size()+1];
+  std::copy(rabit_task_id.begin(), rabit_task_id.end(), cmd);
+  cmd[rabit_task_id.size()] = '\0';
+
+  std::string rabit_reduce_ring_mincount = "rabit_reduce_ring_mincount=1";
+  char cmd2[rabit_reduce_ring_mincount.size()+1];
+  std::copy(rabit_reduce_ring_mincount.begin(), rabit_reduce_ring_mincount.end(), cmd2);
+  cmd2[rabit_reduce_ring_mincount.size()] = '\0';
+
+  char* argv[] = {cmd, cmd2};
+  base.Init(2, argv);
+  EXPECT_EQ(base.task_id, "1");
+  EXPECT_EQ(base.reduce_ring_mincount, 1);
+}

test/cpp/test_main.cpp

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+#include "gtest/gtest.h"
+
+int main(int argc, char** argv)
+{
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}