test: 拆分 VM 测试并新增多项测试

crates/oxide_vm/tests/var_binding_tests.rs

@@ -0,0 +1,40 @@
+use oxide_compiler::compiler::Compiler;
+use oxide_parser::Allocator;
+use oxide_vm::vm::Vm;
+
+fn eval(source: &str) -> String {
+    let allocator = Allocator::default();
+    let program = match oxide_parser::parse(&allocator, source) {
+        Ok(p) => p,
+        Err(e) => return format!("parse error: {}", e[0].message),
+    };
+    let module = match Compiler::new().compile(&program) {
+        Ok(m) => m,
+        Err(e) => return format!("compile error: {e}"),
+    };
+    let mut vm = Vm::new();
+    match vm.run(&module) {
+        Ok(result) => format!("{result}"),
+        Err(e) => format!("vm error: {e}"),
+    }
+}
+
+#[test]
+fn eval_var_declaration() {
+    assert_eq!(eval("var x = 42"), "42");
+}
+
+#[test]
+fn eval_multi_stmt_last_value() {
+    assert_eq!(eval("1; 2; 3"), "3");
+}
+
+#[test]
+fn eval_reassignment() {
+    assert_eq!(eval("var x = 1; x = 2; x"), "2");
+}
+
+#[test]
+fn eval_multi_var_declaration() {
+    assert_eq!(eval("var x = 1; var y = 2; x + y"), "3");
+}