integrate gtest framwork

map/test/CMakeLists.txt

@@ -0,0 +1,9 @@
+add_executable(
+  test_mp_basic
+  test_basic.cpp
+)
+target_link_libraries(
+  test_mp_basic
+  GTest::gtest_main
+)
+gtest_discover_tests(test_mp_basic)

map/test/test_basic.cpp

@@ -0,0 +1,15 @@
+#include <gtest/gtest.h>
+#include "map.hpp"
+
+TEST(BasicTests, GTestItSelf) {
+  // Expect two strings not to be equal.
+  EXPECT_STRNE("hello", "world");
+  // Expect equality.
+  EXPECT_EQ(7 * 6, 42);
+}
+
+TEST(BasicTests, ConstructorAndEmptySize) {
+  sjtu::map<int, int> map;
+  EXPECT_EQ(map.empty(), true);
+  EXPECT_EQ(map.size(), 0);
+}