feat(tests): add tests

added tests for the struct displays, eval function, lexer, and parser

src/math/tests/display.rs

@@ -0,0 +1,97 @@
+use rust_decimal::{Decimal, dec};
+
+use crate::math::types::{Expression, Operator};
+
+#[test]
+fn test_operator_display() {
+    let cases = vec![
+        (Operator::Add, "+"),
+        (Operator::Subtract, "-"),
+        (Operator::Multiply, "*"),
+        (Operator::Divide, "/"),
+        (Operator::Power, "^"),
+        (Operator::Modulo, "%"),
+    ];
+
+    for (operation, expected) in cases {
+        assert_eq!(operation.to_string(), expected);
+    }
+}
+
+#[test]
+fn test_expr_display_number() {
+    let cases = vec![
+        (Expression::Number(dec!(1)), "1"),
+        (Expression::Number(dec!(0.5)), "0.5"),
+        (
+            Expression::Number(Decimal::PI),
+            "3.1415926535897932384626433833",
+        ),
+    ];
+
+    for (expr, expected) in cases {
+        assert_eq!(expr.to_string(), expected);
+    }
+}
+
+#[test]
+fn test_expr_display_variable() {
+    let expr = Expression::Variable("x".to_owned());
+    assert_eq!(expr.to_string(), "x");
+}
+
+#[test]
+fn test_expr_display_fraction() {
+    let cases = vec![
+        (
+            Expression::Fraction(
+                Box::new(Expression::Number(dec!(1))),
+                Box::new(Expression::Number(dec!(2))),
+            ),
+            "(1 / 2)",
+        ),
+        (
+            Expression::Fraction(
+                Box::new(Expression::Number(dec!(5))),
+                Box::new(Expression::Number(dec!(3))),
+            ),
+            "(5 / 3)",
+        ),
+    ];
+
+    for (expr, expected) in cases {
+        assert_eq!(expr.to_string(), expected);
+    }
+}
+
+#[test]
+fn test_expr_display_operation() {
+    let cases = vec![
+        (
+            Expression::Operation(
+                Operator::Multiply,
+                Box::new(Expression::Number(dec!(1))),
+                Box::new(Expression::Number(dec!(2))),
+            ),
+            "(1 * 2)",
+        ),
+        (
+            Expression::Operation(
+                Operator::Modulo,
+                Box::new(Expression::Number(dec!(6))),
+                Box::new(Expression::Number(dec!(3))),
+            ),
+            "(6 % 3)",
+        ),
+    ];
+
+    for (expr, expected) in cases {
+        assert_eq!(expr.to_string(), expected);
+    }
+}
+
+#[test]
+fn test_expr_display_function() {
+    let expr = Expression::Function("sin".to_owned(), vec![Expression::Number(dec!(1))]);
+    assert_eq!(expr.to_string(), "sin(1)");
+}