test: add basic tests for tools.calculation module

Co-authored-by: dgw <[email protected]>

test/tools/test_tools_calculation.py

@@ -0,0 +1,38 @@
+"""Tests Sopel's calculation tools"""
+from __future__ import annotations
+
+import ast
+import operator
+
+import pytest
+
+from sopel.tools.calculation import EquationEvaluator, ExpressionEvaluator
+
+
+def test_expression_eval():
+    """Ensure ExpressionEvaluator respects limited operator set."""
+    OPS = {
+        ast.Add: operator.add,
+        ast.Sub: operator.sub,
+    }
+    evaluator = ExpressionEvaluator(bin_ops=OPS)
+
+    assert evaluator("1 + 1") == 2
+    assert evaluator("43 - 1") == 42
+    assert evaluator("1 + 1 - 2") == 0
+
+    with pytest.raises(ExpressionEvaluator.Error):
+        evaluator("2 * 2")
+
+
+def test_equation_eval():
+    """Test that EquationEvaluator correctly parses input and calculates results."""
+    evaluator = EquationEvaluator()
+
+    assert evaluator("1 + 1") == 2
+    assert evaluator("43 - 1") == 42
+    assert evaluator("(((1 + 1 + 2) * 3 / 5) ** 8 - 13) // 21 % 35") == 16.0
+    assert evaluator("-42") == -42
+    assert evaluator("-(-42)") == 42
+    assert evaluator("+42") == 42
+    assert evaluator("3 ^ 2") == 9