Feature/math boundary tests

contracts/credence_bond/src/test_math.rs

@@ -1,7 +1,14 @@
 //! Tests for overflow-safe arithmetic helpers.
+//!
+//! This module verifies the deterministic behavior, boundary handling, and failure
+//! recovery invariants of the arithmetic operations re-exported in `math.rs`.
+//! All operations must handle valid, invalid, and boundary-case inputs without
+//! producing unsafe or inconsistent results.
 
 use crate::math;
 
+// --- bps ---
+
 #[test]
 fn test_bps_basic() {
     let fee = math::bps(10_000_i128, 100_u32, "mul", "div");
@@ -15,20 +22,261 @@ fn test_bps_overflow_panics() {
     let _ = math::bps(i128::MAX, 10_000_u32, "fee calculation overflow", "div");
 }
 
+#[test]
+fn test_bps_boundaries() {
+    // 0 amount
+    assert_eq!(math::bps(0, 10_000, "mul", "div"), 0);
+    // 0 bps
+    assert_eq!(math::bps(10_000, 0, "mul", "div"), 0);
+    // Negative amount
+    assert_eq!(math::bps(-10_000, 100, "mul", "div"), -100);
+}
+
+// --- bps_u64 ---
+
+#[test]
+fn test_bps_u64_basic() {
+    assert_eq!(math::bps_u64(10_000, 100, "mul fail", "div fail"), 100);
+}
+
+#[test]
+#[should_panic(expected = "mul u64 overflow")]
+fn test_bps_u64_overflow_panics() {
+    let _ = math::bps_u64(u64::MAX, 10_000, "mul u64 overflow", "div fail");
+}
+
+#[test]
+fn test_bps_u64_boundaries() {
+    // 0 amount
+    assert_eq!(math::bps_u64(0, 10_000, "mul", "div"), 0);
+    // 0 bps
+    assert_eq!(math::bps_u64(10_000, 0, "mul", "div"), 0);
+    // Max amount with 0 bps
+    assert_eq!(math::bps_u64(u64::MAX, 0, "mul", "div"), 0);
+}
+
+// --- add_i128 ---
+
+#[test]
+fn test_add_basic() {
+    assert_eq!(math::add_i128(100, 200, "add fail"), 300);
+}
+
+#[test]
+#[should_panic(expected = "add overflow")]
+fn test_add_overflow_panics() {
+    let _ = math::add_i128(i128::MAX, 1, "add overflow");
+}
+
+#[test]
+#[should_panic(expected = "add underflow")]
+fn test_add_underflow_panics() {
+    let _ = math::add_i128(i128::MIN, -1, "add underflow");
+}
+
+#[test]
+fn test_add_boundaries() {
+    assert_eq!(math::add_i128(i128::MAX, 0, "add fail"), i128::MAX);
+    assert_eq!(math::add_i128(i128::MIN, 0, "add fail"), i128::MIN);
+    assert_eq!(math::add_i128(i128::MAX, -1, "add fail"), i128::MAX - 1);
+    assert_eq!(math::add_i128(i128::MIN, 1, "add fail"), i128::MIN + 1);
+}
+
+// --- sub_i128 ---
+
+#[test]
+fn test_sub_basic() {
+    assert_eq!(math::sub_i128(500, 200, "sub fail"), 300);
+}
+
 #[test]
 #[should_panic(expected = "sub underflow")]
 fn test_sub_underflow_panics() {
     let _ = math::sub_i128(i128::MIN, 1, "sub underflow");
 }
 
+#[test]
+#[should_panic(expected = "sub overflow")]
+fn test_sub_overflow_panics() {
+    let _ = math::sub_i128(i128::MAX, -1, "sub overflow");
+}
+
+#[test]
+fn test_sub_boundaries() {
+    assert_eq!(math::sub_i128(i128::MAX, 0, "sub fail"), i128::MAX);
+    assert_eq!(math::sub_i128(i128::MIN, 0, "sub fail"), i128::MIN);
+    assert_eq!(math::sub_i128(i128::MAX, 1, "sub fail"), i128::MAX - 1);
+    assert_eq!(math::sub_i128(i128::MIN, -1, "sub fail"), i128::MIN + 1);
+    assert_eq!(math::sub_i128(0, 0, "sub fail"), 0);
+}
+
+// --- mul_i128 ---
+
+#[test]
+fn test_mul_basic() {
+    assert_eq!(math::mul_i128(50, 2, "mul fail"), 100);
+}
+
 #[test]
 #[should_panic(expected = "mul overflow")]
 fn test_mul_overflow_panics() {
     let _ = math::mul_i128(i128::MAX, 2, "mul overflow");
 }
 
+#[test]
+#[should_panic(expected = "mul underflow")]
+fn test_mul_underflow_panics() {
+    let _ = math::mul_i128(i128::MAX, -2, "mul underflow");
+}
+
+#[test]
+fn test_mul_boundaries() {
+    assert_eq!(math::mul_i128(i128::MAX, 1, "mul fail"), i128::MAX);
+    assert_eq!(math::mul_i128(i128::MIN, 1, "mul fail"), i128::MIN);
+    assert_eq!(math::mul_i128(i128::MAX, 0, "mul fail"), 0);
+    assert_eq!(math::mul_i128(i128::MIN, 0, "mul fail"), 0);
+    assert_eq!(math::mul_i128(-1, -1, "mul fail"), 1);
+}
+
+// --- mul_u64 ---
+
+#[test]
+fn test_mul_u64_basic() {
+    assert_eq!(math::mul_u64(50, 2, "mul fail"), 100);
+}
+
 #[test]
 #[should_panic(expected = "attestation weight overflow")]
 fn test_mul_u64_overflow_panics() {
     let _ = math::mul_u64(u64::MAX, 2, "attestation weight overflow");
 }
+
+#[test]
+fn test_mul_u64_boundaries() {
+    assert_eq!(math::mul_u64(u64::MAX, 1, "mul fail"), u64::MAX);
+    assert_eq!(math::mul_u64(u64::MAX, 0, "mul fail"), 0);
+    assert_eq!(math::mul_u64(0, u64::MAX, "mul fail"), 0);
+}
+
+// --- div_i128 ---
+
+#[test]
+fn test_div_basic() {
+    assert_eq!(math::div_i128(100, 3, "div fail"), 33);
+    assert_eq!(math::div_i128(-100, 3, "div fail"), -33);
+}
+
+#[test]
+#[should_panic(expected = "divide by zero")]
+fn test_div_by_zero_panics() {
+    let _ = math::div_i128(100, 0, "divide by zero");
+}
+
+#[test]
+#[should_panic(expected = "div overflow")]
+fn test_div_overflow_panics() {
+    // i128::MIN / -1 overflows.
+    let _ = math::div_i128(i128::MIN, -1, "div overflow");
+}
+
+#[test]
+fn test_div_boundaries() {
+    assert_eq!(math::div_i128(0, 100, "div fail"), 0);
+    assert_eq!(math::div_i128(i128::MAX, 1, "div fail"), i128::MAX);
+    assert_eq!(math::div_i128(i128::MIN, 1, "div fail"), i128::MIN);
+}
+
+// --- ceil_div_i128 ---
+
+#[test]
+fn test_ceil_div_basic() {
+    assert_eq!(math::ceil_div_i128(100, 3, "ceil div fail"), 34);
+    assert_eq!(math::ceil_div_i128(100, 4, "ceil div fail"), 25);
+    assert_eq!(math::ceil_div_i128(0, 5, "ceil div fail"), 0);
+}
+
+#[test]
+#[should_panic(expected = "divide by zero")]
+fn test_ceil_div_by_zero_panics() {
+    let _ = math::ceil_div_i128(100, 0, "divide by zero");
+}
+
+#[test]
+#[should_panic(expected = "ceil div overflow")]
+fn test_ceil_div_overflow_panics() {
+    // i128::MAX + (b - 1) overflows when b > 1
+    let _ = math::ceil_div_i128(i128::MAX, 2, "ceil div overflow");
+}
+
+#[test]
+fn test_ceil_div_boundaries() {
+    assert_eq!(math::ceil_div_i128(i128::MAX, 1, "ceil div fail"), i128::MAX);
+    assert_eq!(math::ceil_div_i128(0, 1, "ceil div fail"), 0);
+}
+
+// --- sat_mul_bps ---
+
+#[test]
+fn test_sat_mul_bps_basic() {
+    assert_eq!(math::sat_mul_bps(10_000, 5_000), 5_000); // 50% of 10000
+    assert_eq!(math::sat_mul_bps(-10_000, 5_000), -5_000); // 50% of -10000
+}
+
+#[test]
+fn test_sat_mul_bps_saturation() {
+    // Should saturate to i128::MAX instead of panicking, ensuring recovery and safety at limits
+    assert_eq!(math::sat_mul_bps(i128::MAX, 20_000), i128::MAX);
+    // Saturates to i128::MIN
+    assert_eq!(math::sat_mul_bps(i128::MIN, 20_000), i128::MIN);
+}
+
+#[test]
+fn test_sat_mul_bps_boundaries() {
+    assert_eq!(math::sat_mul_bps(0, 20_000), 0);
+    assert_eq!(math::sat_mul_bps(10_000, 0), 0);
+}
+
+// --- split_bps ---
+
+#[test]
+fn test_split_bps_basic() {
+    let (part, remainder) = math::split_bps(1000, 2000, "mul fail", "div fail", "sub fail");
+    assert_eq!(part, 200);
+    assert_eq!(remainder, 800);
+}
+
+#[test]
+fn test_split_bps_boundaries() {
+    // 0%
+    let (part_zero, rem_zero) = math::split_bps(1000, 0, "mul", "div", "sub");
+    assert_eq!(part_zero, 0);
+    assert_eq!(rem_zero, 1000);
+
+    // 100%
+    let (part_full, rem_full) = math::split_bps(1000, 10_000, "mul", "div", "sub");
+    assert_eq!(part_full, 1000);
+    assert_eq!(rem_full, 0);
+
+    // Amount is 0
+    let (part_zero_amt, rem_zero_amt) = math::split_bps(0, 5_000, "mul", "div", "sub");
+    assert_eq!(part_zero_amt, 0);
+    assert_eq!(rem_zero_amt, 0);
+
+    // Negative amount
+    let (part_neg, rem_neg) = math::split_bps(-1000, 2000, "mul", "div", "sub");
+    assert_eq!(part_neg, -200);
+    assert_eq!(rem_neg, -800);
+}
+
+#[test]
+#[should_panic(expected = "mul fail")]
+fn test_split_bps_overflow_panics() {
+    let _ = math::split_bps(i128::MAX, 10_000, "mul fail", "div fail", "sub fail");
+}
+
+// --- constants ---
+
+#[test]
+fn test_bps_denominator() {
+    assert_eq!(math::BPS_DENOMINATOR, 10_000);
+}