diff --git a/Makefile b/Makefile
index 1a6fbfb..4f84806 100644
--- a/Makefile
+++ b/Makefile
@@ -84,6 +84,12 @@ $(UNIT_TEST_DIR)/test_http: $(UNIT_TEST_DIR)/test_http.c http.c log.c $(UNITY_SR
 $(UNIT_TEST_DIR)/test_static: $(UNIT_TEST_DIR)/test_static.c http.c log.c $(UNITY_SRC)
 	$(CC) $(CFLAGS) -D_GNU_SOURCE -I. -I$(UNIT_TEST_DIR)/../unity -o $@ $(UNIT_TEST_DIR)/test_static.c http.c log.c $(UNITY_SRC) -lm -lz
 
+$(UNIT_TEST_DIR)/test_log: $(UNIT_TEST_DIR)/test_log.c log.c $(UNITY_SRC)
+	$(CC) $(CFLAGS) -D_GNU_SOURCE -I. -I$(UNIT_TEST_DIR)/../unity -o $@ $(UNIT_TEST_DIR)/test_log.c log.c $(UNITY_SRC) -lm
+
+$(UNIT_TEST_DIR)/test_config: $(UNIT_TEST_DIR)/test_config.c config.c log.c $(UNITY_SRC)
+	$(CC) $(CFLAGS) -D_GNU_SOURCE -I. -I$(UNIT_TEST_DIR)/../unity -o $@ $(UNIT_TEST_DIR)/test_config.c config.c log.c $(UNITY_SRC) -lm
+
 # 编译规则
 %.o: %.c
 	$(CC) $(CFLAGS) -c $< -o $@
@@ -105,4 +111,4 @@ clean:
 # 重新构建
 rebuild: clean all
 
-.PHONY: all clean install uninstall rebuild deps build-all test bench unit-test
+.PHONY: all clean install uninstall rebuild deps build-all test bench unit-test test-all
diff --git a/http.c b/http.c
index bd4b7e6..226b75b 100644
--- a/http.c
+++ b/http.c
@@ -245,7 +245,7 @@ int http_format_response_header(char *buf, size_t buf_size, const http_response_
 
     /* 状态行 */
     if (resp->has_range) {
-        n += snprintf(buf + n, buf_size - n,
+        n += snprintf(buf + n, buf_size - (size_t)n > buf_size ? 0 : buf_size - (size_t)n,
             "HTTP/1.1 %d %s\r\n"
             "Content-Type: %s\r\n"
             "Content-Length: %ld\r\n"
@@ -256,7 +256,7 @@ int http_format_response_header(char *buf, size_t buf_size, const http_response_
             (long)resp->content_length,
             (long)resp->range_start, (long)resp->range_end, (long)resp->total_length);
     } else {
-        n += snprintf(buf + n, buf_size - n,
+        n += snprintf(buf + n, buf_size - (size_t)n > buf_size ? 0 : buf_size - (size_t)n,
             "HTTP/1.1 %d %s\r\n"
             "Content-Type: %s\r\n"
             "Content-Length: %ld\r\n"
@@ -268,21 +268,37 @@ int http_format_response_header(char *buf, size_t buf_size, const http_response_
 
     /* 缓存头 */
     if (resp->etag && resp->etag[0]) {
-        n += snprintf(buf + n, buf_size - n, "ETag: %s\r\n", resp->etag);
+        if ((size_t)n < buf_size) {
+            n += snprintf(buf + n, buf_size - (size_t)n, "ETag: %s\r\n", resp->etag);
+        } else {
+            n += (int)strlen(resp->etag) + 8;
+        }
     }
     if (resp->last_modified && resp->last_modified[0]) {
-        n += snprintf(buf + n, buf_size - n, "Last-Modified: %s\r\n", resp->last_modified);
+        if ((size_t)n < buf_size) {
+            n += snprintf(buf + n, buf_size - (size_t)n, "Last-Modified: %s\r\n", resp->last_modified);
+        } else {
+            n += (int)strlen(resp->last_modified) + 16;
+        }
     }
     if (resp->content_encoding && resp->content_encoding[0]) {
-        n += snprintf(buf + n, buf_size - n, "Content-Encoding: %s\r\n", resp->content_encoding);
+        if ((size_t)n < buf_size) {
+            n += snprintf(buf + n, buf_size - (size_t)n, "Content-Encoding: %s\r\n", resp->content_encoding);
+        } else {
+            n += (int)strlen(resp->content_encoding) + 20;
+        }
     }
 
     /* 连接头 + 空行 */
-    n += snprintf(buf + n, buf_size - n,
-        "Connection: %s\r\n"
-        "Server: Cocoon/1.0\r\n"
-        "\r\n",
-        resp->keep_alive ? "keep-alive" : "close");
+    if ((size_t)n < buf_size) {
+        n += snprintf(buf + n, buf_size - (size_t)n,
+            "Connection: %s\r\n"
+            "Server: Cocoon/1.0\r\n"
+            "\r\n",
+            resp->keep_alive ? "keep-alive" : "close");
+    } else {
+        n += 35; /* approximate */
+    }
 
     if ((size_t)n >= buf_size) return -1;
     return n;
diff --git a/tests/unit/test_config b/tests/unit/test_config
new file mode 100755
index 0000000..89e7b78
Binary files /dev/null and b/tests/unit/test_config differ
diff --git a/tests/unit/test_config.c b/tests/unit/test_config.c
new file mode 100644
index 0000000..b0c4ac6
--- /dev/null
+++ b/tests/unit/test_config.c
@@ -0,0 +1,206 @@
+#include "unity.h"
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* 辅助：写临时配置文件，返回路径 */
+static const char *write_temp_config(const char *content) {
+    static char path[256];
+    static int counter = 0;
+    snprintf(path, sizeof(path), "/tmp/cocoon_test_config_%d_%d.json",
+             (int)getpid(), counter++);
+    FILE *fp = fopen(path, "w");
+    if (fp) {
+        fwrite(content, 1, strlen(content), fp);
+        fclose(fp);
+    }
+    return path;
+}
+
+static void cleanup(const char *path) {
+    remove(path);
+}
+
+/* ===== config_load_from_file ===== */
+
+void test_load_valid_config(void) {
+    const char *p = write_temp_config(
+        "{\n"
+        "  \"root_dir\": \"/var/www\",\n"
+        "  \"port\": 8080,\n"
+        "  \"threaded\": true,\n"
+        "  \"num_workers\": 8,\n"
+        "  \"max_connections\": 5000,\n"
+        "  \"timeout_ms\": 60000,\n"
+        "  \"log_level\": \"debug\"\n"
+        "}\n"
+    );
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_TRUE(config_load_from_file(p, &cfg));
+    TEST_ASSERT_EQUAL_STRING("/var/www", cfg.root_dir);
+    TEST_ASSERT_EQUAL(8080, cfg.port);
+    TEST_ASSERT_TRUE(cfg.threaded);
+    TEST_ASSERT_EQUAL(8, cfg.num_workers);
+    TEST_ASSERT_EQUAL(5000, cfg.max_connections);
+    TEST_ASSERT_EQUAL(60000, cfg.timeout_ms);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_DEBUG, cfg.log_level);
+    free((void *)cfg.root_dir);
+    cleanup(p);
+}
+
+void test_load_valid_minimal(void) {
+    const char *p = write_temp_config("{\"port\": 3000}");
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_TRUE(config_load_from_file(p, &cfg));
+    TEST_ASSERT_EQUAL(3000, cfg.port);
+    free((void *)cfg.root_dir);
+    cleanup(p);
+}
+
+void test_load_valid_with_comments(void) {
+    const char *p = write_temp_config(
+        "{\n"
+        "  // this is a comment\n"
+        "  \"port\": 9090\n"
+        "}\n"
+    );
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_TRUE(config_load_from_file(p, &cfg));
+    TEST_ASSERT_EQUAL(9090, cfg.port);
+    free((void *)cfg.root_dir);
+    cleanup(p);
+}
+
+void test_load_invalid_json(void) {
+    const char *p = write_temp_config("not json");
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_FALSE(config_load_from_file(p, &cfg));
+    cleanup(p);
+}
+
+void test_load_missing_file(void) {
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_FALSE(config_load_from_file(
+        "/tmp/cocoon_nonexist_12345.json", &cfg));
+}
+
+void test_load_empty_file(void) {
+    const char *p = write_temp_config("");
+    cocoon_config_t cfg = {0};
+    TEST_ASSERT_FALSE(config_load_from_file(p, &cfg));
+    cleanup(p);
+}
+
+void test_load_null_args(void) {
+    TEST_ASSERT_FALSE(config_load_from_file(NULL, NULL));
+    TEST_ASSERT_FALSE(config_load_from_file("/tmp/x", NULL));
+}
+
+/* ===== config_merge ===== */
+
+void test_merge_override_all(void) {
+    cocoon_config_t base = {
+        .root_dir = strdup("/old"),
+        .port = 8080,
+        .threaded = false,
+        .num_workers = 2,
+        .max_connections = 100,
+        .timeout_ms = 30000,
+        .log_level = LOG_LEVEL_INFO
+    };
+    cocoon_config_t cmdline = {
+        .root_dir = "/new",
+        .port = 9090,
+        .threaded = true,
+        .num_workers = 4,
+        .max_connections = 200,
+        .timeout_ms = 60000,
+        .log_level = LOG_LEVEL_DEBUG
+    };
+    config_merge(&base, &cmdline,
+                 true, true, true, true, true, true);
+    TEST_ASSERT_EQUAL_STRING("/new", base.root_dir);
+    TEST_ASSERT_EQUAL(9090, base.port);
+    TEST_ASSERT_TRUE(base.threaded);
+    TEST_ASSERT_EQUAL(4, base.num_workers);
+    TEST_ASSERT_EQUAL(200, base.max_connections);
+    TEST_ASSERT_EQUAL(60000, base.timeout_ms);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_DEBUG, base.log_level);
+    free((void *)base.root_dir);
+}
+
+void test_merge_no_override(void) {
+    cocoon_config_t base = {
+        .root_dir = strdup("/old"),
+        .port = 8080,
+        .threaded = false,
+        .num_workers = 2,
+        .log_level = LOG_LEVEL_INFO
+    };
+    cocoon_config_t cmdline = {
+        .root_dir = "/new",
+        .port = 9090,
+        .num_workers = 4,
+        .log_level = LOG_LEVEL_DEBUG
+    };
+    config_merge(&base, &cmdline,
+                 false, false, false, false, false, false);
+    TEST_ASSERT_EQUAL_STRING("/old", base.root_dir);
+    TEST_ASSERT_EQUAL(8080, base.port);
+    TEST_ASSERT_FALSE(base.threaded);
+    TEST_ASSERT_EQUAL(2, base.num_workers);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, base.log_level);
+    free((void *)base.root_dir);
+}
+
+void test_merge_partial_override(void) {
+    cocoon_config_t base = {
+        .root_dir = strdup("/old"),
+        .port = 8080,
+        .num_workers = 2,
+        .log_level = LOG_LEVEL_INFO
+    };
+    cocoon_config_t cmdline = {
+        .root_dir = "/new",
+        .port = 9090,
+        .num_workers = 4,
+        .log_level = LOG_LEVEL_DEBUG
+    };
+    config_merge(&base, &cmdline,
+                 true, false, false, true, false, false);
+    TEST_ASSERT_EQUAL_STRING("/new", base.root_dir);   /* overridden */
+    TEST_ASSERT_EQUAL(8080, base.port);                /* not overridden */
+    TEST_ASSERT_EQUAL(2, base.num_workers);            /* not overridden */
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, base.log_level);   /* not overridden */
+    free((void *)base.root_dir);
+}
+
+void test_merge_null_safety(void) {
+    /* 不应 crash */
+    config_merge(NULL, NULL, true, true, true, true, true, true);
+    TEST_ASSERT_TRUE(1);
+}
+
+void setUp(void) {}
+void tearDown(void) {}
+
+int main(void) {
+    UNITY_BEGIN();
+
+    RUN_TEST(test_load_valid_config);
+    RUN_TEST(test_load_valid_minimal);
+    RUN_TEST(test_load_valid_with_comments);
+    RUN_TEST(test_load_invalid_json);
+    RUN_TEST(test_load_missing_file);
+    RUN_TEST(test_load_empty_file);
+    RUN_TEST(test_load_null_args);
+
+    RUN_TEST(test_merge_override_all);
+    RUN_TEST(test_merge_no_override);
+    RUN_TEST(test_merge_partial_override);
+    RUN_TEST(test_merge_null_safety);
+
+    return UNITY_END();
+}
diff --git a/tests/unit/test_http b/tests/unit/test_http
index a95cc19..a3f1c8a 100755
Binary files a/tests/unit/test_http and b/tests/unit/test_http differ
diff --git a/tests/unit/test_http.c b/tests/unit/test_http.c
index 596633a..4e08690 100644
--- a/tests/unit/test_http.c
+++ b/tests/unit/test_http.c
@@ -179,11 +179,8 @@ void test_parse_keep_alive_override(void) {
     http_request_t parsed = {0};
     http_parse_request(req, strlen(req), &parsed);
     
-    /* 解析器先设置 HTTP/1.1 默认 keep-alive=true，然后解析头部时，如果 Connection: close 则设为 false */
-    /* 但当前实现是 Connection: keep-alive 才设为 true，否则保持 false */
-    /* 实际上 HTTP/1.1 默认 keep-alive，这里应该是 true 因为代码逻辑是先设置默认值，再解析头部 */
-    /* 修改测试以匹配实际行为：代码在解析头部后没有强制覆盖默认值 */
-    TEST_ASSERT_TRUE(parsed.keep_alive); /* HTTP/1.1 默认保持 */
+    /* HTTP/1.1 默认 keep-alive=true，但 Connection: close 应覆盖为 false */
+    TEST_ASSERT_FALSE(parsed.keep_alive);
     http_request_free(&parsed);
 }
 
diff --git a/tests/unit/test_http_asan b/tests/unit/test_http_asan
index 7815e2d..4d7ce2e 100755
Binary files a/tests/unit/test_http_asan and b/tests/unit/test_http_asan differ
diff --git a/tests/unit/test_log b/tests/unit/test_log
new file mode 100755
index 0000000..3fff7b4
Binary files /dev/null and b/tests/unit/test_log differ
diff --git a/tests/unit/test_log.c b/tests/unit/test_log.c
new file mode 100644
index 0000000..23ea0ec
--- /dev/null
+++ b/tests/unit/test_log.c
@@ -0,0 +1,81 @@
+#include "unity.h"
+#include "log.h"
+
+/* ===== log_get_level / log_set_level ===== */
+
+void test_default_level_is_info(void) {
+    /* 静态全局变量默认初始化为 LOG_LEVEL_INFO */
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, log_get_level());
+}
+
+void test_set_level_error(void) {
+    log_set_level(LOG_LEVEL_ERROR);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_ERROR, log_get_level());
+}
+
+void test_set_level_warn(void) {
+    log_set_level(LOG_LEVEL_WARN);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_WARN, log_get_level());
+}
+
+void test_set_level_debug(void) {
+    log_set_level(LOG_LEVEL_DEBUG);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_DEBUG, log_get_level());
+}
+
+void test_set_level_info(void) {
+    log_set_level(LOG_LEVEL_INFO);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, log_get_level());
+}
+
+/* ===== log_set_prefix ===== */
+
+void test_set_prefix(void) {
+    log_set_prefix("[Test]");
+    /* 无返回值，仅确认不 crash */
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, log_get_level());
+}
+
+void test_set_prefix_null(void) {
+    log_set_prefix(NULL);
+    /* NULL 表示无前缀，不 crash */
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, log_get_level());
+}
+
+/* ===== 边界：多次设置 ===== */
+
+void test_level_persistence(void) {
+    log_set_level(LOG_LEVEL_DEBUG);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_DEBUG, log_get_level());
+    log_set_level(LOG_LEVEL_ERROR);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_ERROR, log_get_level());
+    log_set_level(LOG_LEVEL_INFO);
+    TEST_ASSERT_EQUAL(LOG_LEVEL_INFO, log_get_level());
+}
+
+void setUp(void) {
+    /* 每个测试前重置为默认 */
+    log_set_level(LOG_LEVEL_INFO);
+    log_set_prefix("[Cocoon]");
+}
+
+void tearDown(void) {
+    /* 每个测试后重置 */
+    log_set_level(LOG_LEVEL_INFO);
+    log_set_prefix("[Cocoon]");
+}
+
+int main(void) {
+    UNITY_BEGIN();
+
+    RUN_TEST(test_default_level_is_info);
+    RUN_TEST(test_set_level_error);
+    RUN_TEST(test_set_level_warn);
+    RUN_TEST(test_set_level_debug);
+    RUN_TEST(test_set_level_info);
+    RUN_TEST(test_set_prefix);
+    RUN_TEST(test_set_prefix_null);
+    RUN_TEST(test_level_persistence);
+
+    return UNITY_END();
+}
diff --git a/tests/unit/test_static b/tests/unit/test_static
index c85c84d..f3a486b 100755
Binary files a/tests/unit/test_static and b/tests/unit/test_static differ