test: add chat_room unit tests and integrate into build

- Add 11 unit tests for chat_room.c covering: create/destroy, message
  add/overflow, broadcast sequence, get_message bounds, client
  add/remove/capacity, and null argument handling
- Add unit-test target to root Makefile so `make test` runs unit tests
  before integration tests
- Add common.c to unit test link dependencies (needed for tnt_state_path)
- Guard _DARWIN_C_SOURCE define to prevent -Wmacro-redefined warning

Makefile

@@ -71,10 +71,14 @@ check:
 	@command -v clang-tidy >/dev/null 2>&1 && clang-tidy src/*.c -- -Iinclude $(INCLUDES) || echo "clang-tidy not installed"
 
 # Test
-test: all
-	@echo "Running tests..."
+test: all unit-test
+	@echo "Running integration tests..."
 	@cd tests && ./test_basic.sh
 
+unit-test:
+	@echo "Running unit tests..."
+	@$(MAKE) -C tests/unit run
+
 # Show build info
 info:
 	@echo "Compiler: $(CC)"

src/message.c

@@ -1,7 +1,7 @@
 #ifndef _DEFAULT_SOURCE
 #define _DEFAULT_SOURCE  /* for timegm() on glibc */
 #endif
-#ifdef __APPLE__
+#if defined(__APPLE__) && !defined(_DARWIN_C_SOURCE)
 #define _DARWIN_C_SOURCE /* for timegm() on macOS */
 #endif
 #include "message.h"

tests/unit/Makefile

@@ -1,13 +1,21 @@
 # Unit Tests Makefile
 CC = gcc
-CFLAGS = -Wall -Wextra -std=c11 -I../../include
+CFLAGS = -Wall -Wextra -std=c11 -D_XOPEN_SOURCE=700 -I../../include
 LDFLAGS = -pthread
 
+# Detect macOS for _DARWIN_C_SOURCE (needed for timegm)
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Darwin)
+CFLAGS += -D_DARWIN_C_SOURCE
+endif
+
 # Source files
 UTF8_SRC = ../../src/utf8.c
 MESSAGE_SRC = ../../src/message.c
+COMMON_SRC = ../../src/common.c
+CHAT_ROOM_SRC = ../../src/chat_room.c
 
-TESTS = test_utf8 test_message
+TESTS = test_utf8 test_message test_chat_room
 
 .PHONY: all clean run
 
@@ -16,7 +24,10 @@ all: $(TESTS)
 test_utf8: test_utf8.c $(UTF8_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-test_message: test_message.c $(MESSAGE_SRC) $(UTF8_SRC)
+test_message: test_message.c $(MESSAGE_SRC) $(UTF8_SRC) $(COMMON_SRC)
+	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+test_chat_room: test_chat_room.c $(CHAT_ROOM_SRC) $(MESSAGE_SRC) $(UTF8_SRC) $(COMMON_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
 run: all
@@ -25,6 +36,9 @@ run: all
 	@echo ""
 	@echo "=== Running Message Tests ==="
 	./test_message
+	@echo ""
+	@echo "=== Running Chat Room Tests ==="
+	./test_chat_room
 
 clean:
 	rm -f $(TESTS) *.o test_messages.log

tests/unit/test_chat_room.c

@@ -0,0 +1,208 @@
+/* Unit tests for chat_room functions */
+
+/* Minimal client_t stub — only pointer identity matters for add/remove.
+ * We define `struct client` before including chat_room.h so the forward
+ * declaration resolves without pulling in ssh_server.h / libssh. */
+#include "../../include/common.h"
+
+struct client {
+    char username[MAX_USERNAME_LEN];
+    int dummy;
+};
+typedef struct client client_t;
+
+#include "../../include/chat_room.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;
+
+static message_t make_msg(const char *user, const char *content) {
+    message_t m = { .timestamp = time(NULL) };
+    strncpy(m.username, user, MAX_USERNAME_LEN - 1);
+    strncpy(m.content, content, MAX_MESSAGE_LEN - 1);
+    return m;
+}
+
+TEST(room_create_destroy) {
+    chat_room_t *room = room_create();
+    assert(room != NULL);
+    assert(room->client_count == 0);
+    assert(room->client_capacity > 0);
+    room_destroy(room);
+}
+
+TEST(room_add_message_single) {
+    chat_room_t *room = room_create();
+    message_t msg = make_msg("alice", "hello");
+
+    room_add_message(room, &msg);
+    assert(room->message_count == 1);
+    assert(strcmp(room->messages[0].username, "alice") == 0);
+    assert(strcmp(room->messages[0].content, "hello") == 0);
+
+    room_destroy(room);
+}
+
+TEST(room_add_message_overflow) {
+    chat_room_t *room = room_create();
+
+    for (int i = 0; i < MAX_MESSAGES + 10; i++) {
+        char content[32];
+        snprintf(content, sizeof(content), "msg %d", i);
+        message_t msg = make_msg("user", content);
+        room_add_message(room, &msg);
+    }
+
+    assert(room->message_count == MAX_MESSAGES);
+
+    char expected[32];
+    snprintf(expected, sizeof(expected), "msg %d", 10);
+    assert(strcmp(room->messages[0].content, expected) == 0);
+
+    snprintf(expected, sizeof(expected), "msg %d", MAX_MESSAGES + 9);
+    assert(strcmp(room->messages[MAX_MESSAGES - 1].content, expected) == 0);
+
+    room_destroy(room);
+}
+
+TEST(room_broadcast_increments_seq) {
+    chat_room_t *room = room_create();
+    g_room = room;
+
+    uint64_t seq1 = room_get_update_seq(room);
+    message_t msg = make_msg("bob", "hi");
+    room_broadcast(room, &msg);
+    uint64_t seq2 = room_get_update_seq(room);
+
+    assert(seq2 > seq1);
+    assert(room_get_message_count(room) == 1);
+
+    g_room = NULL;
+    room_destroy(room);
+}
+
+TEST(room_get_message_valid) {
+    chat_room_t *room = room_create();
+    message_t msg = make_msg("carol", "test");
+    room_add_message(room, &msg);
+
+    message_t out;
+    assert(room_get_message(room, 0, &out) == true);
+    assert(strcmp(out.username, "carol") == 0);
+    assert(strcmp(out.content, "test") == 0);
+
+    room_destroy(room);
+}
+
+TEST(room_get_message_invalid_index) {
+    chat_room_t *room = room_create();
+
+    message_t out;
+    assert(room_get_message(room, 0, &out) == false);
+    assert(room_get_message(room, -1, &out) == false);
+    assert(room_get_message(room, 999, &out) == false);
+
+    room_destroy(room);
+}
+
+TEST(room_get_message_null_args) {
+    chat_room_t *room = room_create();
+    message_t out;
+
+    assert(room_get_message(NULL, 0, &out) == false);
+    assert(room_get_message(room, 0, NULL) == false);
+
+    room_destroy(room);
+}
+
+TEST(room_client_count) {
+    chat_room_t *room = room_create();
+    assert(room_get_client_count(room) == 0);
+
+    client_t c1 = {0};
+    client_t c2 = {0};
+    assert(room_add_client(room, &c1) == 0);
+    assert(room_get_client_count(room) == 1);
+    assert(room_add_client(room, &c2) == 0);
+    assert(room_get_client_count(room) == 2);
+
+    room_remove_client(room, &c1);
+    assert(room_get_client_count(room) == 1);
+
+    room_remove_client(room, &c2);
+    assert(room_get_client_count(room) == 0);
+
+    room_destroy(room);
+}
+
+TEST(room_remove_nonexistent_client) {
+    chat_room_t *room = room_create();
+    client_t c1 = {0};
+    client_t c2 = {0};
+
+    room_add_client(room, &c1);
+    room_remove_client(room, &c2);
+    assert(room_get_client_count(room) == 1);
+
+    room_destroy(room);
+}
+
+TEST(room_add_client_full) {
+    chat_room_t *room = room_create();
+    client_t clients[MAX_CLIENTS + 1];
+    memset(clients, 0, sizeof(clients));
+
+    for (int i = 0; i < room->client_capacity; i++) {
+        assert(room_add_client(room, &clients[i]) == 0);
+    }
+
+    assert(room_add_client(room, &clients[room->client_capacity]) == -1);
+    assert(room_get_client_count(room) == room->client_capacity);
+
+    room_destroy(room);
+}
+
+TEST(room_message_count_threadsafe) {
+    chat_room_t *room = room_create();
+
+    assert(room_get_message_count(room) == 0);
+
+    message_t msg = make_msg("dave", "msg");
+    room_broadcast(room, &msg);
+    assert(room_get_message_count(room) == 1);
+
+    room_broadcast(room, &msg);
+    room_broadcast(room, &msg);
+    assert(room_get_message_count(room) == 3);
+
+    room_destroy(room);
+}
+
+int main(void) {
+    printf("=== Chat Room Unit Tests ===\n");
+
+    RUN_TEST(room_create_destroy);
+    RUN_TEST(room_add_message_single);
+    RUN_TEST(room_add_message_overflow);
+    RUN_TEST(room_broadcast_increments_seq);
+    RUN_TEST(room_get_message_valid);
+    RUN_TEST(room_get_message_invalid_index);
+    RUN_TEST(room_get_message_null_args);
+    RUN_TEST(room_client_count);
+    RUN_TEST(room_remove_nonexistent_client);
+    RUN_TEST(room_add_client_full);
+    RUN_TEST(room_message_count_threadsafe);
+
+    printf("\nAll %d tests passed!\n", tests_passed);
+    return 0;
+}