From 2b2d1a651a670f92b4c328beae6531eb5779ca37 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu, 19 Feb 2026 09:28:16 +0000
Subject: [PATCH] test(cas): add tests for Cas.evaluate

Added comprehensive tests for Cas.evaluate covering:
- Differentiation commands (d/dx)
- Integration commands (int)
- Simplification
- Equation handling
- Error cases

This ensures that the command parsing logic for CAS operations is verified and regressions can be detected.

Co-authored-by: smjxpro <9335473+smjxpro@users.noreply.github.com>
---
 test/cas_test.dart | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 test/cas_test.dart

diff --git a/test/cas_test.dart b/test/cas_test.dart
new file mode 100644
index 0000000..99da96e
--- /dev/null
+++ b/test/cas_test.dart
@@ -0,0 +1,63 @@
+import 'package:functionx/src/cas/cas.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Cas', () {
+    group('evaluate', () {
+      test('differentiates single variable: d/dx(x^2)', () {
+        // math_expressions derivative logic produces this unsimplified form
+        expect(Cas.evaluate('d/dx(x^2)'), equals('((x^2.0) * (2.0 * (1.0 / x)))'));
+      });
+
+      test('differentiates trig function: d/dx(sin(x))', () {
+        // sin(x) derives to cos(x) * 1, which simplifies to cos(x)
+        expect(Cas.evaluate('d/dx(sin(x))'), equals('cos(x)'));
+      });
+
+      test('differentiates constant: d/dx(5)', () {
+        expect(Cas.evaluate('d/dx(5)'), equals('0.0'));
+      });
+
+      test('differentiates with different variable: d/dt(t^2)', () {
+        expect(Cas.evaluate('d/dt(t^2)'), equals('((t^2.0) * (2.0 * (1.0 / t)))'));
+      });
+
+      test('integrates variable: int(x)dx', () {
+        expect(Cas.evaluate('int(x)dx'), equals('0.5*x^2'));
+      });
+
+      test('integrates variable (implicit dx): int(x)', () {
+        expect(Cas.evaluate('int(x)'), equals('0.5*x^2'));
+      });
+
+      test('integrates trig function: int(cos(x))dx', () {
+        expect(Cas.evaluate('int(cos(x))dx'), equals('sin(x)'));
+      });
+
+      test('integrates constant: int(5)dx', () {
+        expect(Cas.evaluate('int(5)dx'), equals('5.0*x'));
+      });
+
+      test('simplifies expression: x + x', () {
+        // simplification logic does not combine like terms in this version
+        expect(Cas.evaluate('x + x'), equals('(x + x)'));
+      });
+
+      test('evaluates equation: d/dx(x^2) = 2*x', () {
+        expect(Cas.evaluate('d/dx(x^2) = 2*x'), equals('((x^2.0) * (2.0 * (1.0 / x))) = (2.0 * x)'));
+      });
+
+      test('throws on invalid derivative format', () {
+        expect(() => Cas.evaluate('d/dx'), throwsFormatException);
+      });
+
+      test('throws on invalid integral format', () {
+        expect(() => Cas.evaluate('int(x'), throwsFormatException);
+      });
+
+      test('throws on unsupported integration', () {
+         expect(() => Cas.evaluate('int(tan(x))dx'), throwsFormatException);
+      });
+    });
+  });
+}