diff --git a/tests/unit/test_multipart.c b/tests/unit/test_multipart.c
new file mode 100644
index 0000000..4797268
--- /dev/null
+++ b/tests/unit/test_multipart.c
@@ -0,0 +1,183 @@
+#include "unity.h"
+#include "multipart.h"
+#include <string.h>
+#include <stdlib.h>
+
+/* ===== multipart_extract_boundary ===== */
+
+void test_extract_boundary_simple(void) {
+    char buf[256];
+    TEST_ASSERT_TRUE(multipart_extract_boundary(
+        "multipart/form-data; boundary=----WebKitFormBoundary", buf, sizeof(buf)));
+    TEST_ASSERT_EQUAL_STRING("----WebKitFormBoundary", buf);
+}
+
+void test_extract_boundary_quoted(void) {
+    char buf[256];
+    TEST_ASSERT_TRUE(multipart_extract_boundary(
+        "multipart/form-data; boundary=\"abc123\"", buf, sizeof(buf)));
+    TEST_ASSERT_EQUAL_STRING("abc123", buf);
+}
+
+void test_extract_boundary_with_extra_params(void) {
+    char buf[256];
+    TEST_ASSERT_TRUE(multipart_extract_boundary(
+        "multipart/form-data; boundary=xyz; charset=utf-8", buf, sizeof(buf)));
+    TEST_ASSERT_EQUAL_STRING("xyz", buf);
+}
+
+void test_extract_boundary_null(void) {
+    char buf[256];
+    TEST_ASSERT_FALSE(multipart_extract_boundary(NULL, buf, sizeof(buf)));
+    TEST_ASSERT_FALSE(multipart_extract_boundary("text/plain", buf, sizeof(buf)));
+}
+
+void test_extract_boundary_too_small_buffer(void) {
+    char buf[4];
+    TEST_ASSERT_FALSE(multipart_extract_boundary(
+        "multipart/form-data; boundary=abcdef", buf, sizeof(buf)));
+}
+
+/* ===== multipart_parse ===== */
+
+static const char *SAMPLE_MULTIPART =
+    "------WebKitFormBoundary7MA4YWxkTrZu0gW\r\n"
+    "Content-Disposition: form-data; name=\"file\"; filename=\"test.txt\"\r\n"
+    "Content-Type: text/plain\r\n"
+    "\r\n"
+    "Hello, World!\r\n"
+    "------WebKitFormBoundary7MA4YWxkTrZu0gW\r\n"
+    "Content-Disposition: form-data; name=\"description\"\r\n"
+    "\r\n"
+    "Test file upload\r\n"
+    "------WebKitFormBoundary7MA4YWxkTrZu0gW--\r\n";
+
+void test_parse_simple_multipart(void) {
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(0, multipart_parse(SAMPLE_MULTIPART, strlen(SAMPLE_MULTIPART),
+                                          "----WebKitFormBoundary7MA4YWxkTrZu0gW",
+                                          &parts, &num_parts));
+    TEST_ASSERT_EQUAL(2, num_parts);
+
+    TEST_ASSERT_EQUAL_STRING("file", parts[0].name);
+    TEST_ASSERT_EQUAL_STRING("test.txt", parts[0].filename);
+    TEST_ASSERT_EQUAL_STRING("text/plain", parts[0].content_type);
+    TEST_ASSERT_EQUAL(13, parts[0].data_len);
+    TEST_ASSERT_EQUAL_STRING("Hello, World!", parts[0].data);
+
+    TEST_ASSERT_EQUAL_STRING("description", parts[1].name);
+    TEST_ASSERT_NULL(parts[1].filename);
+    TEST_ASSERT_EQUAL(16, parts[1].data_len);
+    TEST_ASSERT_EQUAL_STRING("Test file upload", parts[1].data);
+
+    multipart_parts_free(parts, num_parts);
+}
+
+void test_parse_no_filename(void) {
+    const char *body =
+        "--boundary\r\n"
+        "Content-Disposition: form-data; name=\"field1\"\r\n"
+        "\r\n"
+        "value1\r\n"
+        "--boundary--\r\n";
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(0, multipart_parse(body, strlen(body), "boundary", &parts, &num_parts));
+    TEST_ASSERT_EQUAL(1, num_parts);
+    TEST_ASSERT_EQUAL_STRING("field1", parts[0].name);
+    TEST_ASSERT_NULL(parts[0].filename);
+    TEST_ASSERT_EQUAL_STRING("value1", parts[0].data);
+    multipart_parts_free(parts, num_parts);
+}
+
+void test_parse_empty_body(void) {
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(-1, multipart_parse("", 0, "boundary", &parts, &num_parts));
+}
+
+void test_parse_null_args(void) {
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(-1, multipart_parse(NULL, 0, "boundary", &parts, &num_parts));
+    TEST_ASSERT_EQUAL(-1, multipart_parse("x", 1, NULL, &parts, &num_parts));
+}
+
+void test_parse_invalid_boundary(void) {
+    const char *body = "not a multipart body";
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(-1, multipart_parse(body, strlen(body), "boundary", &parts, &num_parts));
+}
+
+void test_parse_binary_data(void) {
+    /* 包含 \0 的二进制数据 */
+    char body[256];
+    int n = snprintf(body, sizeof(body),
+        "--bin\r\n"
+        "Content-Disposition: form-data; name=\"bin\"; filename=\"data.bin\"\r\n"
+        "Content-Type: application/octet-stream\r\n"
+        "\r\n");
+    /* 追加二进制数据 */
+    body[n++] = 0x00;
+    body[n++] = 0x01;
+    body[n++] = 0x02;
+    body[n++] = 0x03;
+    int end = snprintf(body + n, sizeof(body) - n, "\r\n--bin--\r\n");
+    n += end;
+
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(0, multipart_parse(body, (size_t)n, "bin", &parts, &num_parts));
+    TEST_ASSERT_EQUAL(1, num_parts);
+    TEST_ASSERT_EQUAL(4, parts[0].data_len);
+    TEST_ASSERT_EQUAL(0x00, (unsigned char)parts[0].data[0]);
+    TEST_ASSERT_EQUAL(0x01, (unsigned char)parts[0].data[1]);
+    TEST_ASSERT_EQUAL(0x02, (unsigned char)parts[0].data[2]);
+    TEST_ASSERT_EQUAL(0x03, (unsigned char)parts[0].data[3]);
+    multipart_parts_free(parts, num_parts);
+}
+
+void test_parse_multiple_files(void) {
+    const char *body =
+        "--multi\r\n"
+        "Content-Disposition: form-data; name=\"files\"; filename=\"a.txt\"\r\n"
+        "\r\n"
+        "A\r\n"
+        "--multi\r\n"
+        "Content-Disposition: form-data; name=\"files\"; filename=\"b.txt\"\r\n"
+        "\r\n"
+        "B\r\n"
+        "--multi--\r\n";
+    multipart_part_t *parts = NULL;
+    int num_parts = 0;
+    TEST_ASSERT_EQUAL(0, multipart_parse(body, strlen(body), "multi", &parts, &num_parts));
+    TEST_ASSERT_EQUAL(2, num_parts);
+    TEST_ASSERT_EQUAL_STRING("a.txt", parts[0].filename);
+    TEST_ASSERT_EQUAL_STRING("b.txt", parts[1].filename);
+    multipart_parts_free(parts, num_parts);
+}
+
+void setUp(void) {}
+void tearDown(void) {}
+
+int main(void) {
+    UNITY_BEGIN();
+
+    RUN_TEST(test_extract_boundary_simple);
+    RUN_TEST(test_extract_boundary_quoted);
+    RUN_TEST(test_extract_boundary_with_extra_params);
+    RUN_TEST(test_extract_boundary_null);
+    RUN_TEST(test_extract_boundary_too_small_buffer);
+
+    RUN_TEST(test_parse_simple_multipart);
+    RUN_TEST(test_parse_no_filename);
+    RUN_TEST(test_parse_empty_body);
+    RUN_TEST(test_parse_null_args);
+    RUN_TEST(test_parse_invalid_boundary);
+    RUN_TEST(test_parse_binary_data);
+    RUN_TEST(test_parse_multiple_files);
+
+    return UNITY_END();
+}