diff --git a/CMakeLists.txt b/CMakeLists.txt
index e8d5345..1f44102 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -69,3 +69,10 @@ set(COMMON_LIBRARIES
 
 add_executable(password-analyzer ${COMMON_SOURCES} analyzer.cpp)
 target_link_libraries(password-analyzer PRIVATE ${COMMON_LIBRARIES})
+
+add_executable(tests ${COMMON_SOURCES} tests.cpp)
+target_link_libraries(tests PRIVATE Catch2::Catch2WithMain ${COMMON_LIBRARIES})
+
+include(CTest)
+include(Catch)
+catch_discover_tests(tests)
diff --git a/analyzer.cpp b/analyzer.cpp
new file mode 100644
index 0000000..13b7c0a
--- /dev/null
+++ b/analyzer.cpp
@@ -0,0 +1,14 @@
+#include "defs.hpp"
+
+int main() {
+    stat_length(DataSource::YAHOO);
+    stat_length(DataSource::CSDN);
+
+    stat_struct(DataSource::YAHOO);
+    stat_struct(DataSource::CSDN);
+
+    stat_keystroke(DataSource::YAHOO);
+    stat_keystroke(DataSource::CSDN);
+
+    return 0;
+}
diff --git a/tests.cpp b/tests.cpp
new file mode 100644
index 0000000..319fcbd
--- /dev/null
+++ b/tests.cpp
@@ -0,0 +1,95 @@
+#include <vector>
+#include <catch2/catch_test_macros.hpp>
+#include "defs.hpp"
+
+auto count_passwords(const DataSource &source) -> size_t {
+    auto cnt = 0;
+    for (auto const &_ : passwords(source)) cnt++;
+    return cnt;
+}
+
+std::string get_struct(const std::string &password);
+auto        string_to_cord(const std::string &password) -> std::vector<Cord>;
+auto        cord_to_string(const std::vector<Cord> &cords) -> std::string;
+auto        is_neighbour(const Cord &a, const Cord &b) -> bool;
+
+TEST_CASE("number of CSDN is correct", "[passwords]") { REQUIRE(count_passwords(DataSource::CSDN) == 6428632); }
+
+TEST_CASE("number of YAHOO is correct", "[passwords]") { REQUIRE(count_passwords(DataSource::YAHOO) == 442836); }
+
+TEST_CASE("passwords(10) of CSDN is correct", "[passwords]") {
+    const std::string ans[] = {"12344321", "670203313747", "730413", "2535263", "KIC43dk6!",
+                               "s12345",   "apple",        "lj7202", "12345",   "hebeibdh"};
+
+    size_t i = 0;
+    for (auto const &p : passwords(DataSource::CSDN) | std::views::take(10)) {
+        REQUIRE(ans[i++] == p);
+    }
+}
+
+TEST_CASE("passwords(10) of YAHOO is correct", "[passwords]") {
+    const std::string ans[] = {"@fl!pm0de@", "pass",     "steveol",  "chotzi",   "lb2512",
+                               "scotch",     "passwerd", "flipmode", "flipmode", "alden2"};
+
+    size_t i = 0;
+    for (auto const &p : passwords(DataSource::YAHOO) | std::views::take(10)) {
+        REQUIRE(ans[i++] == p);
+    }
+}
+
+TEST_CASE("get_struct works", "[stat_struct]") {
+    const std::string test_cases[][2] = {{"A", "L1"},      {"1", "D1"},       {"!", "S1"},
+                                         {"AABBCC", "L6"}, {"A1@", "L1D1S1"}, {"AbCd@", "L4S1"}};
+
+    for (auto const &[password, expected] : test_cases) {
+        auto ans = get_struct(password);
+        REQUIRE(ans == expected);
+    }
+}
+
+TEST_CASE("string_to_cord works", "[stat_keystroke]") {
+    const std::pair<std::string, std::vector<Cord>> test_cases[] = {
+        {"asdf", {{2, 1}, {2, 2}, {2, 3}, {2, 4}}},
+        {"AwDr%", {{2, 1}, {1, 2}, {2, 3}, {1, 4}, {0, 5}}},
+        {"p_[=}\\", {{1, 10}, {0, 11}, {1, 11}, {0, 12}, {1, 12}, {1, 13}}},
+        {",L>;/\"", {{3, 8}, {2, 9}, {3, 9}, {2, 10}, {3, 10}, {2, 11}}},
+    };
+
+    for (auto const &[password, expected] : test_cases) {
+        auto ans = string_to_cord(password);
+        REQUIRE(ans == expected);
+    }
+}
+
+TEST_CASE("cord_to_string works", "[stat_keystroke]") {
+    const std::pair<std::string, std::vector<Cord>> test_cases[] = {
+        {"asdf", {{2, 1}, {2, 2}, {2, 3}, {2, 4}}},
+        {"awdr5", {{2, 1}, {1, 2}, {2, 3}, {1, 4}, {0, 5}}},
+        {"p-[=]\\", {{1, 10}, {0, 11}, {1, 11}, {0, 12}, {1, 12}, {1, 13}}},
+        {",l.;/'", {{3, 8}, {2, 9}, {3, 9}, {2, 10}, {3, 10}, {2, 11}}},
+    };
+
+    for (auto const &[expected, cords] : test_cases) {
+        auto ans = cord_to_string(cords);
+        REQUIRE(ans == expected);
+    }
+}
+
+TEST_CASE("is_neighbour works", "[stat_keystroke]") {
+    const auto dict = string_to_cord("`1qwad;./"s);
+
+    const std::pair<std::pair<Cord, Cord>, bool> test_cases[] = {
+        {{dict[0], dict[1]}, true},  // `1
+        {{dict[0], dict[2]}, true},  // `q
+        {{dict[3], dict[4]}, true},  // wa
+        {{dict[3], dict[5]}, true},  // wd
+        {{dict[4], dict[5]}, false}, // ad
+        {{dict[6], dict[7]}, true},  // ;.
+        {{dict[6], dict[8]}, true},  // ;/
+    };
+
+    for (auto const &[cords, expected] : test_cases) {
+        auto ans = is_neighbour(cords.first, cords.second);
+        REQUIRE(ans == expected);
+    }
+}