test(parser): add implicit multiplication tests

added tests:
- implicit multiplication between a number + variable
- implicit multiplication between two paren groups

src/math/tests/parser.rs

@@ -116,3 +116,48 @@ fn test_parser_negative_exponent() {
     let result = parser::from(tokens).parse();
     assert_eq!(result, expected);
 }
+
+#[test]
+fn test_parser_implicit_multiply() {
+    let tokens = vec![Token::Number(dec!(5)), Token::Identifier("x".to_owned())];
+    let expected = Expression::Operation(
+        Operator::Multiply,
+        Box::new(Expression::Number(dec!(5))),
+        Box::new(Expression::Variable("x".to_owned())),
+    );
+
+    let result = parser::from(tokens).parse();
+    assert_eq!(result, expected);
+}
+
+#[test]
+fn test_parser_implicit_multiply_group() {
+    let tokens = vec![
+        Token::OpenParen,
+        Token::Number(dec!(5)),
+        Token::Operator(Operator::Add),
+        Token::Number(dec!(5)),
+        Token::CloseParen,
+        Token::OpenParen,
+        Token::Number(dec!(10)),
+        Token::Operator(Operator::Add),
+        Token::Number(dec!(10)),
+        Token::CloseParen,
+    ];
+    let expected = Expression::Operation(
+        Operator::Multiply,
+        Box::new(Expression::Operation(
+            Operator::Add,
+            Box::new(Expression::Number(dec!(5))),
+            Box::new(Expression::Number(dec!(5))),
+        )),
+        Box::new(Expression::Operation(
+            Operator::Add,
+            Box::new(Expression::Number(dec!(10))),
+            Box::new(Expression::Number(dec!(10))),
+        )),
+    );
+
+    let result = parser::from(tokens).parse();
+    assert_eq!(result, expected);
+}