diff --git a/tests/unit/Makefile b/tests/unit/Makefile
new file mode 100644
index 0000000..0fe36d8
--- /dev/null
+++ b/tests/unit/Makefile
@@ -0,0 +1,30 @@
+# Unit Tests Makefile
+CC = gcc
+CFLAGS = -Wall -Wextra -std=c11 -I../../include
+LDFLAGS = -pthread
+
+# Source files
+UTF8_SRC = ../../src/utf8.c
+MESSAGE_SRC = ../../src/message.c
+
+TESTS = test_utf8 test_message
+
+.PHONY: all clean run
+
+all: $(TESTS)
+
+test_utf8: test_utf8.c $(UTF8_SRC)
+	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+test_message: test_message.c $(MESSAGE_SRC) $(UTF8_SRC)
+	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+run: all
+	@echo "=== Running UTF-8 Tests ==="
+	./test_utf8
+	@echo ""
+	@echo "=== Running Message Tests ==="
+	./test_message
+
+clean:
+	rm -f $(TESTS) *.o test_messages.log
diff --git a/tests/unit/test_message b/tests/unit/test_message
new file mode 100755
index 0000000..0067319
Binary files /dev/null and b/tests/unit/test_message differ
diff --git a/tests/unit/test_message.c b/tests/unit/test_message.c
new file mode 100644
index 0000000..4b7ad3e
--- /dev/null
+++ b/tests/unit/test_message.c
@@ -0,0 +1,240 @@
+/* Unit tests for message functions */
+#include "../../include/message.h"
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#define TEST(name) static void test_##name()
+#define RUN_TEST(name) do { \
+    printf("Running %s... ", #name); \
+    test_##name(); \
+    printf("✓\n"); \
+    tests_passed++; \
+} while(0)
+
+static int tests_passed = 0;
+static const char *test_log = "test_messages.log";
+
+/* Helper: Clean up test log file */
+static void cleanup_test_log(void) {
+    unlink(test_log);
+}
+
+/* Helper: Create test log with N messages */
+static void create_test_log(int count) {
+    FILE *fp = fopen(test_log, "w");
+    assert(fp != NULL);
+
+    for (int i = 0; i < count; i++) {
+        fprintf(fp, "2026-02-08T10:00:%02d+08:00|user%d|Test message %d\n",
+                i, i, i);
+    }
+    fclose(fp);
+}
+
+/* Test message initialization */
+TEST(message_init) {
+    message_init();
+    /* No assertion needed, just ensure it doesn't crash */
+}
+
+/* Test loading from empty file */
+TEST(message_load_empty) {
+    cleanup_test_log();
+
+    /* Temporarily override LOG_FILE */
+    FILE *fp = fopen(test_log, "w");
+    fclose(fp);
+
+    message_t *messages = NULL;
+    /* Can't easily override LOG_FILE constant, so this is a documentation test */
+
+    cleanup_test_log();
+}
+
+/* Test message format */
+TEST(message_format_basic) {
+    message_t msg;
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "testuser");
+    strcpy(msg.content, "Hello World");
+
+    char buffer[512];
+    message_format(&msg, buffer, sizeof(buffer), 80);
+
+    /* Should contain timestamp, username, and content */
+    assert(strstr(buffer, "testuser") != NULL);
+    assert(strstr(buffer, "Hello World") != NULL);
+}
+
+TEST(message_format_long_content) {
+    message_t msg;
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "user");
+
+    /* Create long message */
+    memset(msg.content, 'A', MAX_MESSAGE_LEN - 1);
+    msg.content[MAX_MESSAGE_LEN - 1] = '\0';
+
+    char buffer[2048];
+    message_format(&msg, buffer, sizeof(buffer), 80);
+
+    /* Should not overflow */
+    assert(strlen(buffer) < sizeof(buffer));
+}
+
+TEST(message_format_unicode) {
+    message_t msg;
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "用户");
+    strcpy(msg.content, "你好世界");
+
+    char buffer[512];
+    message_format(&msg, buffer, sizeof(buffer), 80);
+
+    assert(strstr(buffer, "用户") != NULL);
+    assert(strstr(buffer, "你好世界") != NULL);
+}
+
+TEST(message_format_width_limits) {
+    message_t msg;
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "user");
+    strcpy(msg.content, "Test");
+
+    char buffer[512];
+
+    /* Test various widths */
+    message_format(&msg, buffer, sizeof(buffer), 40);
+    assert(strlen(buffer) < 512);
+
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) < 512);
+
+    message_format(&msg, buffer, sizeof(buffer), 120);
+    assert(strlen(buffer) < 512);
+}
+
+/* Test message save */
+TEST(message_save_basic) {
+    cleanup_test_log();
+
+    /* This is harder to test without modifying LOG_FILE constant */
+    /* For now, document expected behavior */
+    message_t msg;
+    msg.timestamp = time(NULL);
+    strcpy(msg.username, "testuser");
+    strcpy(msg.content, "Test message");
+
+    /* Would save to LOG_FILE */
+    /* int ret = message_save(&msg); */
+    /* assert(ret == 0); */
+
+    cleanup_test_log();
+}
+
+/* Test edge cases */
+TEST(message_edge_cases) {
+    message_t msg;
+    char buffer[512];
+
+    /* Empty username */
+    msg.timestamp = 1234567890;
+    msg.username[0] = '\0';
+    strcpy(msg.content, "Test");
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) > 0);
+
+    /* Empty content */
+    strcpy(msg.username, "user");
+    msg.content[0] = '\0';
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) > 0);
+
+    /* Maximum length username */
+    memset(msg.username, 'A', MAX_USERNAME_LEN - 1);
+    msg.username[MAX_USERNAME_LEN - 1] = '\0';
+    strcpy(msg.content, "Test");
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) < sizeof(buffer));
+
+    /* Maximum length content */
+    strcpy(msg.username, "user");
+    memset(msg.content, 'B', MAX_MESSAGE_LEN - 1);
+    msg.content[MAX_MESSAGE_LEN - 1] = '\0';
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    /* Should handle gracefully */
+}
+
+TEST(message_special_characters) {
+    message_t msg;
+    char buffer[512];
+
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "user<test>");
+    strcpy(msg.content, "Message with\nnewline\tand\ttabs");
+
+    message_format(&msg, buffer, sizeof(buffer), 80);
+
+    /* Should not crash or overflow */
+    assert(strlen(buffer) < sizeof(buffer));
+}
+
+/* Test buffer safety */
+TEST(message_buffer_safety) {
+    message_t msg;
+    char small_buffer[16];
+
+    msg.timestamp = 1234567890;
+    strcpy(msg.username, "verylongusername");
+    strcpy(msg.content, "Very long message content that exceeds buffer");
+
+    /* Should not overflow even with small buffer */
+    message_format(&msg, small_buffer, sizeof(small_buffer), 80);
+    assert(strlen(small_buffer) < sizeof(small_buffer));
+}
+
+/* Test timestamp handling */
+TEST(message_timestamp_formats) {
+    message_t msg;
+    char buffer[512];
+
+    strcpy(msg.username, "user");
+    strcpy(msg.content, "Test");
+
+    /* Test various timestamps */
+    msg.timestamp = 0;  /* Epoch */
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) > 0);
+
+    msg.timestamp = time(NULL);  /* Current time */
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) > 0);
+
+    msg.timestamp = 2147483647;  /* Max 32-bit timestamp */
+    message_format(&msg, buffer, sizeof(buffer), 80);
+    assert(strlen(buffer) > 0);
+}
+
+int main(void) {
+    printf("Running message unit tests...\n\n");
+
+    RUN_TEST(message_init);
+    RUN_TEST(message_load_empty);
+    RUN_TEST(message_format_basic);
+    RUN_TEST(message_format_long_content);
+    RUN_TEST(message_format_unicode);
+    RUN_TEST(message_format_width_limits);
+    RUN_TEST(message_save_basic);
+    RUN_TEST(message_edge_cases);
+    RUN_TEST(message_special_characters);
+    RUN_TEST(message_buffer_safety);
+    RUN_TEST(message_timestamp_formats);
+
+    cleanup_test_log();
+
+    printf("\n✓ All %d tests passed!\n", tests_passed);
+    return 0;
+}
diff --git a/tests/unit/test_utf8 b/tests/unit/test_utf8
new file mode 100755
index 0000000..f02a121
Binary files /dev/null and b/tests/unit/test_utf8 differ
diff --git a/tests/unit/test_utf8.c b/tests/unit/test_utf8.c
new file mode 100644
index 0000000..7f42f9e
--- /dev/null
+++ b/tests/unit/test_utf8.c
@@ -0,0 +1,239 @@
+/* Unit tests for UTF-8 functions */
+#include "../../include/utf8.h"
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#define TEST(name) static void test_##name()
+#define RUN_TEST(name) do { \
+    printf("Running %s... ", #name); \
+    test_##name(); \
+    printf("✓\n"); \
+    tests_passed++; \
+} while(0)
+
+static int tests_passed = 0;
+
+/* Test UTF-8 byte length detection */
+TEST(utf8_byte_length_ascii) {
+    assert(utf8_byte_length('A') == 1);
+    assert(utf8_byte_length('z') == 1);
+    assert(utf8_byte_length('0') == 1);
+}
+
+TEST(utf8_byte_length_multibyte) {
+    assert(utf8_byte_length(0xC3) == 2);  /* é first byte */
+    assert(utf8_byte_length(0xE4) == 3);  /* 中 first byte */
+    assert(utf8_byte_length(0xF0) == 4);  /* 𝕏 first byte */
+}
+
+TEST(utf8_byte_length_invalid) {
+    assert(utf8_byte_length(0xFF) == 1);  /* Invalid UTF-8 */
+    assert(utf8_byte_length(0x80) == 1);  /* Continuation byte */
+}
+
+/* Test UTF-8 decoding */
+TEST(utf8_decode_ascii) {
+    int bytes_read;
+    assert(utf8_decode("A", &bytes_read) == 'A');
+    assert(bytes_read == 1);
+}
+
+TEST(utf8_decode_2byte) {
+    int bytes_read;
+    /* é = U+00E9 = 0xC3 0xA9 */
+    const char *e_acute = "\xC3\xA9";
+    uint32_t codepoint = utf8_decode(e_acute, &bytes_read);
+    assert(codepoint == 0x00E9);
+    assert(bytes_read == 2);
+}
+
+TEST(utf8_decode_3byte) {
+    int bytes_read;
+    /* 中 = U+4E2D = 0xE4 0xB8 0xAD */
+    const char *zhong = "\xE4\xB8\xAD";
+    uint32_t codepoint = utf8_decode(zhong, &bytes_read);
+    assert(codepoint == 0x4E2D);
+    assert(bytes_read == 3);
+}
+
+TEST(utf8_decode_4byte) {
+    int bytes_read;
+    /* 𝕏 = U+1D54F = 0xF0 0x9D 0x95 0x8F */
+    const char *math_x = "\xF0\x9D\x95\x8F";
+    uint32_t codepoint = utf8_decode(math_x, &bytes_read);
+    assert(codepoint == 0x1D54F);
+    assert(bytes_read == 4);
+}
+
+/* Test character width calculation */
+TEST(utf8_char_width_ascii) {
+    assert(utf8_char_width('A') == 1);
+    assert(utf8_char_width(' ') == 1);
+    assert(utf8_char_width('0') == 1);
+}
+
+TEST(utf8_char_width_cjk) {
+    assert(utf8_char_width(0x4E2D) == 2);  /* 中 */
+    assert(utf8_char_width(0x6587) == 2);  /* 文 */
+    assert(utf8_char_width(0x5B57) == 2);  /* 字 */
+}
+
+TEST(utf8_char_width_hangul) {
+    assert(utf8_char_width(0xAC00) == 2);  /* 가 */
+    assert(utf8_char_width(0xD7A3) == 2);  /* 힣 */
+}
+
+TEST(utf8_char_width_hiragana) {
+    assert(utf8_char_width(0x3042) == 2);  /* あ */
+    assert(utf8_char_width(0x3093) == 2);  /* ん */
+}
+
+TEST(utf8_char_width_katakana) {
+    assert(utf8_char_width(0x30A2) == 2);  /* ア */
+    assert(utf8_char_width(0x30F3) == 2);  /* ン */
+}
+
+/* Test string width calculation */
+TEST(utf8_string_width_ascii) {
+    assert(utf8_string_width("Hello") == 5);
+    assert(utf8_string_width("") == 0);
+    assert(utf8_string_width("Test123") == 7);
+}
+
+TEST(utf8_string_width_mixed) {
+    /* "Hello世界" = 5 ASCII + 2*2 CJK = 9 */
+    assert(utf8_string_width("Hello世界") == 9);
+
+    /* "测试Test" = 2*2 CJK + 4 ASCII = 8 */
+    assert(utf8_string_width("测试Test") == 8);
+}
+
+TEST(utf8_string_width_cjk_only) {
+    /* "中文字符" = 4 * 2 = 8 */
+    assert(utf8_string_width("中文字符") == 8);
+}
+
+/* Test backspace handling */
+TEST(utf8_remove_last_char) {
+    char buffer[256];
+
+    /* Test ASCII */
+    strcpy(buffer, "Hello");
+    utf8_remove_last_char(buffer);
+    assert(strcmp(buffer, "Hell") == 0);
+
+    /* Test empty string */
+    strcpy(buffer, "");
+    utf8_remove_last_char(buffer);
+    assert(strcmp(buffer, "") == 0);
+
+    /* Test single char */
+    strcpy(buffer, "A");
+    utf8_remove_last_char(buffer);
+    assert(strcmp(buffer, "") == 0);
+}
+
+TEST(utf8_remove_last_char_multibyte) {
+    char buffer[256];
+
+    /* Test 2-byte UTF-8 */
+    strcpy(buffer, "café");
+    utf8_remove_last_char(buffer);
+    assert(strcmp(buffer, "caf") == 0);
+
+    /* Test 3-byte UTF-8 (CJK) */
+    strcpy(buffer, "你好");
+    utf8_remove_last_char(buffer);
+    assert(strcmp(buffer, "你") == 0);
+}
+
+/* Test word removal (Ctrl+W) */
+TEST(utf8_remove_last_word) {
+    char buffer[256];
+
+    /* Test simple case */
+    strcpy(buffer, "hello world");
+    utf8_remove_last_word(buffer);
+    assert(strcmp(buffer, "hello ") == 0);
+
+    /* Test multiple words */
+    strcpy(buffer, "one two three");
+    utf8_remove_last_word(buffer);
+    assert(strcmp(buffer, "one two ") == 0);
+
+    /* Test trailing spaces */
+    strcpy(buffer, "hello   ");
+    utf8_remove_last_word(buffer);
+    assert(strcmp(buffer, "") == 0);
+
+    /* Test single word */
+    strcpy(buffer, "word");
+    utf8_remove_last_word(buffer);
+    assert(strcmp(buffer, "") == 0);
+
+    /* Test empty string */
+    strcpy(buffer, "");
+    utf8_remove_last_word(buffer);
+    assert(strcmp(buffer, "") == 0);
+}
+
+/* Test input validation */
+TEST(utf8_is_valid_sequence) {
+    /* Valid sequences */
+    assert(utf8_is_valid_sequence("A", 1) == true);
+    assert(utf8_is_valid_sequence("\xC3\xA9", 2) == true);  /* é */
+    assert(utf8_is_valid_sequence("\xE4\xB8\xAD", 3) == true);  /* 中 */
+
+    /* Invalid sequences */
+    assert(utf8_is_valid_sequence("\xFF", 1) == false);  /* Invalid start */
+    assert(utf8_is_valid_sequence("\xC3\xFF", 2) == false);  /* Invalid continuation */
+
+    /* Invalid lengths */
+    assert(utf8_is_valid_sequence("", 0) == false);
+    assert(utf8_is_valid_sequence("ABCDE", 5) == false);  /* Too long */
+    assert(utf8_is_valid_sequence(NULL, 1) == false);
+}
+
+/* Test boundary cases */
+TEST(utf8_boundary_cases) {
+    /* Maximum valid codepoints */
+    assert(utf8_char_width(0x10FFFF) == 1);  /* Max Unicode codepoint */
+
+    /* BMP boundary */
+    assert(utf8_char_width(0xFFFF) == 1);
+
+    /* CJK range boundaries */
+    assert(utf8_char_width(0x4DFF) == 1);   /* Just before CJK Extension A */
+    assert(utf8_char_width(0x4E00) == 2);   /* Start of CJK Unified */
+    assert(utf8_char_width(0x9FFF) == 2);   /* End of CJK Unified */
+    assert(utf8_char_width(0xA000) == 1);   /* Just after CJK Unified */
+}
+
+int main(void) {
+    printf("Running UTF-8 unit tests...\n\n");
+
+    RUN_TEST(utf8_byte_length_ascii);
+    RUN_TEST(utf8_byte_length_multibyte);
+    RUN_TEST(utf8_byte_length_invalid);
+    RUN_TEST(utf8_decode_ascii);
+    RUN_TEST(utf8_decode_2byte);
+    RUN_TEST(utf8_decode_3byte);
+    RUN_TEST(utf8_decode_4byte);
+    RUN_TEST(utf8_char_width_ascii);
+    RUN_TEST(utf8_char_width_cjk);
+    RUN_TEST(utf8_char_width_hangul);
+    RUN_TEST(utf8_char_width_hiragana);
+    RUN_TEST(utf8_char_width_katakana);
+    RUN_TEST(utf8_string_width_ascii);
+    RUN_TEST(utf8_string_width_mixed);
+    RUN_TEST(utf8_string_width_cjk_only);
+    RUN_TEST(utf8_remove_last_char);
+    RUN_TEST(utf8_remove_last_char_multibyte);
+    RUN_TEST(utf8_remove_last_word);
+    RUN_TEST(utf8_is_valid_sequence);
+    RUN_TEST(utf8_boundary_cases);
+
+    printf("\n✓ All %d tests passed!\n", tests_passed);
+    return 0;
+}