Add test, fixes#5

rust-calc/src/main.rs

@@ -322,3 +322,31 @@ fn main() {
     let res = calculation(&symbols, &numbers);
     println!("{res}");
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{calculation, parse};
+
+    #[test]
+    fn basics() {
+        let (s, n) = parse("2+2".to_string());
+        assert_eq!(calculation(&s, &n), 4.0);
+        let (s, n) = parse("4-9".to_string());
+        assert_eq!(calculation(&s, &n), -5.0);
+        let (s, n) = parse("7*3".to_string());
+        assert_eq!(calculation(&s, &n), 21.0);
+        let (s, n) = parse("9/3".to_string());
+        assert_eq!(calculation(&s, &n), 3.0);
+
+        let (s, n) = parse("15*20".to_string());
+        assert_ne!(calculation(&s, &n), 0.0);
+    }
+
+    #[test]
+    fn signs_2() {
+        let (s, n) = parse("2+2*4".to_string());
+        assert_eq!(calculation(&s, &n), 10.0);
+        let (s, n) = parse("30/4-9".to_string());
+        assert_eq!(calculation(&s, &n), -1.5);
+    }
+}