tests: apply AI comments

Author: bidzyyys

math/fixed_point/tests/sd29x9_tests/arithmetic_tests.move

@@ -55,9 +55,9 @@ fun sub_handles_edge_cases() {
     expect(zero.sub(min_plus_epsilon), max);
     expect(zero.sub(max), min_plus_epsilon);
 
-    expect(max.negate().add(epsilon.negate()), min);
-    expect(max.sub(epsilon).add(epsilon), max);
-    expect(min.add(epsilon).add(epsilon).negate().add(epsilon), max);
+    expect(max.negate().sub(epsilon), min);
+    expect(max.sub(epsilon).sub(epsilon.negate()), max);
+    expect(min.add(epsilon).add(epsilon).negate().sub(epsilon.negate()), max);
 }
 
 #[test, expected_failure(abort_code = sd29x9_base::EOverflow)]

math/fixed_point/tests/sd29x9_tests/mul_tests.move

@@ -21,6 +21,8 @@ fun mul_handles_multiplication_by_zero() {
         neg(5 * SCALE + 250_000_000),
         pos(500_000_000_000_000_000),
         neg(500_000_000_000_000_000),
+        pos(MAX_POSITIVE_VALUE),
+        neg(MIN_NEGATIVE_VALUE),
     ];
     values.destroy!(|val| {
         expect(val.mul(zero), zero);