Use default rust directory structure for tests

tests/var_scope.rs

@@ -0,0 +1,42 @@
+extern crate rhai;
+
+use rhai::{Engine, Scope};
+
+#[test]
+fn test_var_scope() {
+    let mut engine = Engine::new();
+    let mut scope: Scope = Vec::new();
+
+    if let Ok(_) = engine.eval_with_scope::<()>(&mut scope, "let x = 4 + 5") {
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval_with_scope::<i64>(&mut scope, "x") {
+        assert_eq!(result, 9);
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(_) = engine.eval_with_scope::<()>(&mut scope, "x = x + 1; x = x + 2;") {
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval_with_scope::<i64>(&mut scope, "x") {
+        assert_eq!(result, 12);
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(_) = engine.eval_with_scope::<()>(&mut scope, "{let x = 3}") {
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval_with_scope::<i64>(&mut scope, "x") {
+        assert_eq!(result, 12);
+    } else {
+        assert!(false);
+    }
+}