diff --git a/test/test_codegen.c b/test/test_codegen.c
index 336f2cb..6070a76 100644
--- a/test/test_codegen.c
+++ b/test/test_codegen.c
@@ -88,9 +88,35 @@ void test_codegen_binary_ops() {
     arena_destroy(&a);
 }
 
+void test_codegen_while_loop() {
+    Arena a = arena_create(1);
+    // fn main() -> i64 { while true { return 0; } return 1; }
+    AstNode* while_body_stmts[] = {
+        ast_make_return(&a, ast_make_literal_i64(&a, 0, 1, 1), 1, 1)
+    };
+    AstNode* while_body = ast_make_block(&a, while_body_stmts, 1, 1, 1);
+    AstNode* while_stmt = ast_make_while(&a,
+        ast_make_literal_bool(&a, true, 1, 1), while_body, 1, 1);
+    AstNode* ret = ast_make_return(&a, ast_make_literal_i64(&a, 1, 1, 1), 1, 1);
+    AstNode* stmts[] = { while_stmt, ret };
+    AstNode* fn_body = ast_make_block(&a, stmts, 2, 1, 1);
+    AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, fn_body, 1, 1);
+    AstNode* fns[] = { fn };
+    AstNode* prog = ast_make_program(&a, fns, 1, 1, 1);
+
+    const char* err = NULL;
+    LLVMModuleRef mod = codegen_module(prog, &a, "test_while", &err);
+    ASSERT(mod != NULL);
+    char* verify_err = NULL;
+    ASSERT(!LLVMVerifyModule(mod, LLVMReturnStatusAction, &verify_err));
+    LLVMDisposeModule(mod);
+    arena_destroy(&a);
+}
+
 int main(void) {
     TEST_RUN(test_codegen_simple_function);
     TEST_RUN(test_codegen_if_else);
     TEST_RUN(test_codegen_binary_ops);
+    TEST_RUN(test_codegen_while_loop);
     return test_summary();
 }
diff --git a/test/test_sema.c b/test/test_sema.c
index da0accf..0a4cf78 100644
--- a/test/test_sema.c
+++ b/test/test_sema.c
@@ -51,9 +51,77 @@ void test_simple_ok() {
     arena_destroy(&a);
 }
 
+void test_let_mut_assign_ok() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn main() { let mut x: i64 = 0; x = 42; print_i64(x); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);
+    arena_destroy(&a);
+}
+
+void test_assign_immutable_error() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn main() { let x: i64 = 0; x = 42; return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count > 0);  // 不可变变量赋值应报错
+    arena_destroy(&a);
+}
+
+void test_str_type_ok() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn main() { let msg: str = \"hello\"; print_str(msg); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);
+    arena_destroy(&a);
+}
+
+void test_str_concat_type_ok() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn main() { let a: str = \"a\"; let b: str = \"b\"; let c: str = a + b; print_str(c); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);
+    arena_destroy(&a);
+}
+
 int main(void) {
     TEST_RUN(test_type_error);
     TEST_RUN(test_undefined_var);
     TEST_RUN(test_simple_ok);
+    TEST_RUN(test_let_mut_assign_ok);
+    TEST_RUN(test_assign_immutable_error);
+    TEST_RUN(test_str_type_ok);
+    TEST_RUN(test_str_concat_type_ok);
     return test_summary();
 }