chore: claude-generated pre-audit of ecc.pil in avm - added edge-case tests

barretenberg/cpp/src/barretenberg/vm2/constraining/relations/ecc.test.cpp

@@ -559,6 +559,85 @@ TEST(ScalarMulConstrainingTest, BasicMul)
     check_relation<scalar_mul>(trace);
 }
 
+// Edge case: Verify that 0 * P = infinity (point at infinity)
+TEST(ScalarMulConstrainingTest, MulByZero)
+{
+    EccTraceBuilder builder;
+
+    EventEmitter<EccAddEvent> ecc_add_event_emitter;
+    EventEmitter<ScalarMulEvent> scalar_mul_event_emitter;
+    NoopEventEmitter<EccAddMemoryEvent> ecc_add_memory_event_emitter;
+
+    StrictMock<MockExecutionIdManager> execution_id_manager;
+    StrictMock<MockGreaterThan> gt;
+    PureToRadix to_radix_simulator = PureToRadix();
+    EccSimulator ecc_simulator(execution_id_manager,
+                               gt,
+                               to_radix_simulator,
+                               ecc_add_event_emitter,
+                               scalar_mul_event_emitter,
+                               ecc_add_memory_event_emitter);
+
+    // Multiply by zero - result should be point at infinity
+    FF scalar = FF(0);
+    EmbeddedCurvePoint result = ecc_simulator.scalar_mul(p, scalar);
+
+    // Verify result is infinity
+    ASSERT_TRUE(result.is_infinity());
+
+    TestTraceContainer trace({
+        { { C::precomputed_first_row, 1 } },
+    });
+
+    builder.process_scalar_mul(scalar_mul_event_emitter.dump_events(), trace);
+    builder.process_add(ecc_add_event_emitter.dump_events(), trace);
+
+    EXPECT_EQ(trace.get_num_rows(), /*start_row=*/1 + 254);
+    check_relation<scalar_mul>(trace);
+    check_relation<ecc>(trace);
+}
+
+// Edge case: Verify scalar multiplication works with a large scalar near field modulus
+TEST(ScalarMulConstrainingTest, MulByLargeScalar)
+{
+    EccTraceBuilder builder;
+
+    EventEmitter<EccAddEvent> ecc_add_event_emitter;
+    EventEmitter<ScalarMulEvent> scalar_mul_event_emitter;
+    NoopEventEmitter<EccAddMemoryEvent> ecc_add_memory_event_emitter;
+
+    StrictMock<MockExecutionIdManager> execution_id_manager;
+    StrictMock<MockGreaterThan> gt;
+    PureToRadix to_radix_simulator = PureToRadix();
+    EccSimulator ecc_simulator(execution_id_manager,
+                               gt,
+                               to_radix_simulator,
+                               ecc_add_event_emitter,
+                               scalar_mul_event_emitter,
+                               ecc_add_memory_event_emitter);
+
+    // Use a large scalar (p - 1, where p is the field modulus)
+    // BN254 scalar field modulus - 1: 0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000000
+    FF scalar = FF("0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593efffffff");
+    EmbeddedCurvePoint result = ecc_simulator.scalar_mul(p, scalar);
+
+    // Verify result is a valid point (not infinity for non-zero scalar with non-infinity point)
+    // The exact result depends on the scalar and point, but it should be deterministic
+    EmbeddedCurvePoint expected_result = p * Fq(scalar);
+    EXPECT_EQ(result, expected_result);
+
+    TestTraceContainer trace({
+        { { C::precomputed_first_row, 1 } },
+    });
+
+    builder.process_scalar_mul(scalar_mul_event_emitter.dump_events(), trace);
+    builder.process_add(ecc_add_event_emitter.dump_events(), trace);
+
+    // Note: Row count varies based on number of ECC operations (depends on scalar bit pattern)
+    check_relation<scalar_mul>(trace);
+    check_relation<ecc>(trace);
+}
+
 TEST(ScalarMulConstrainingTest, MultipleInvocations)
 {
     EccTraceBuilder builder;