Add tests for left-hand side of assignment being an identifier.

Relates to #106

src/token/mod.rs

@@ -444,7 +444,7 @@ pub(crate) fn tokenize(string: &str) -> EvalexprResult<Vec<Token>> {
 
 #[cfg(test)]
 mod tests {
-    use crate::token::{char_to_partial_token, tokenize};
+    use crate::token::{char_to_partial_token, tokenize, Token};
     use std::fmt::Write;
 
     #[test]
@@ -474,4 +474,17 @@ mod tests {
 
         assert_eq!(token_string, result_string);
     }
+
+    #[test]
+    fn assignment_lhs_is_identifier() {
+        let tokens = tokenize("a = 1").unwrap();
+        assert_eq!(
+            tokens.as_slice(),
+            [
+                Token::Identifier("a".to_string()),
+                Token::Assign,
+                Token::Int(1)
+            ]
+        );
+    }
 }

tests/integration.rs

@@ -2083,3 +2083,28 @@ fn test_try_from() {
     );
     assert_eq!(EmptyType::try_from(value.clone()), Ok(()));
 }
+
+#[test]
+fn assignment_lhs_is_identifier() {
+    let tree = build_operator_tree("a = 1").unwrap();
+    let operators: Vec<_> = tree.iter().map(|node| node.operator().clone()).collect();
+
+    let mut context = HashMapContext::new();
+    tree.eval_empty_with_context_mut(&mut context).unwrap();
+    assert_eq!(context.get_value("a"), Some(&Value::Int(1)));
+
+    assert!(
+        matches!(
+            operators.as_slice(),
+            [
+                Operator::Assign,
+                Operator::VariableIdentifier { identifier: value },
+                Operator::Const {
+                    value: Value::Int(1)
+                }
+            ] if value == "a"
+        ),
+        "actual: {:#?}",
+        operators
+    );
+}