Use default rust directory structure for tests

tests/ops.rs

@@ -0,0 +1,31 @@
+extern crate rhai;
+
+use rhai::Engine;
+
+#[test]
+fn test_ops() {
+    let mut engine = Engine::new();
+
+    if let Ok(result) = engine.eval::<i64>("60 + 5") {
+        assert_eq!(result, 65);
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval::<i64>("(1 + 2) * (6 - 4) / 2") {
+        assert_eq!(result, 3);
+    } else {
+        assert!(false);
+    }
+}
+
+#[test]
+fn test_op_prec() {
+    let mut engine = Engine::new();
+
+    if let Ok(result) = engine.eval::<i64>("let x = 0; if x == 10 || true { x = 1} x") {
+        assert_eq!(result, 1);
+    } else {
+        assert!(false);
+    }
+}