From 6abff9b791cd23fa42dd09351efff4ec5ffb0e10 Mon Sep 17 00:00:00 2001
From: EDOHWARES <edohemmanuel4real@gmail.com>
Date: Fri, 27 Mar 2026 14:11:15 +0100
Subject: [PATCH] feat: add property-based tests for payout logic

---
 contract/Cargo.lock                           | 429 +++++++++++++++++-
 contract/Cargo.toml                           |   1 +
 .../contracts/predifi-contract/Cargo.toml     |   1 +
 .../contracts/predifi-contract/src/lib.rs     |   2 +
 .../predifi-contract/src/payout_proptests.rs  |  90 ++++
 .../predifi-contract/test_output.txt          |  25 +
 6 files changed, 529 insertions(+), 19 deletions(-)
 create mode 100644 contract/contracts/predifi-contract/src/payout_proptests.rs
 create mode 100644 contract/contracts/predifi-contract/test_output.txt

diff --git a/contract/Cargo.lock b/contract/Cargo.lock
index 7e2ccd0..f9b9e23 100644
--- a/contract/Cargo.lock
+++ b/contract/Cargo.lock
@@ -16,7 +16,7 @@ version = "0.7.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "891477e0c6a8957309ee5c45a6368af3ae14bb510732d2684ffa19af310920f9"
 dependencies = [
- "getrandom",
+ "getrandom 0.2.17",
  "once_cell",
  "version_check",
 ]
@@ -42,6 +42,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.102"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
+
 [[package]]
 name = "arbitrary"
 version = "1.3.2"
@@ -166,7 +172,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94893f1e0c6eeab764ade8dc4c0db24caf4fe7cbbaafc0eba0a9030f447b5185"
 dependencies = [
  "num-traits",
- "rand",
+ "rand 0.8.5",
 ]
 
 [[package]]
@@ -193,6 +199,27 @@ version = "1.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
 
+[[package]]
+name = "bit-set"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08807e080ed7f9d5433fa9b275196cfc35414f66a0c79d864dc51a0d825231a3"
+dependencies = [
+ "bit-vec",
+]
+
+[[package]]
+name = "bit-vec"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e764a1d40d510daf35e07be9eb06e75770908c27d411ee6c92109c9840eaaf7"
+
+[[package]]
+name = "bitflags"
+version = "2.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "843867be96c8daad0d758b57df9392b6d8d271134fce549de6ce169ff98a92af"
+
 [[package]]
 name = "block-buffer"
 version = "0.10.4"
@@ -343,7 +370,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0dc92fb57ca44df6db8059111ab3af99a63d5d0f8375d9972e319a379c6bab76"
 dependencies = [
  "generic-array",
- "rand_core",
+ "rand_core 0.6.4",
  "subtle",
  "zeroize",
 ]
@@ -589,7 +616,7 @@ checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
 dependencies = [
  "curve25519-dalek",
  "ed25519",
- "rand_core",
+ "rand_core 0.6.4",
  "serde",
  "sha2",
  "subtle",
@@ -614,7 +641,7 @@ dependencies = [
  "ff",
  "generic-array",
  "group",
- "rand_core",
+ "rand_core 0.6.4",
  "sec1",
  "subtle",
  "zeroize",
@@ -626,6 +653,16 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys",
+]
+
 [[package]]
 name = "escape-bytes"
 version = "0.1.1"
@@ -638,13 +675,19 @@ version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ca81e6b4777c89fd810c25a4be2b1bd93ea034fbe58e6a75216a34c6b82c539b"
 
+[[package]]
+name = "fastrand"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
+
 [[package]]
 name = "ff"
 version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c0b50bfb653653f9ca9095b427bed08ab8d75a137839d9ad64eb11810d5b6393"
 dependencies = [
- "rand_core",
+ "rand_core 0.6.4",
  "subtle",
 ]
 
@@ -666,6 +709,12 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
+[[package]]
+name = "foldhash"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
+
 [[package]]
 name = "generic-array"
 version = "0.14.9"
@@ -690,6 +739,31 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi 5.3.0",
+ "wasip2",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0de51e6874e94e7bf76d726fc5d13ba782deca734ff60d5bb2fb2607c7406555"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi 6.0.0",
+ "wasip2",
+ "wasip3",
+]
+
 [[package]]
 name = "group"
 version = "0.13.0"
@@ -697,7 +771,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f0f9ef7462f7c099f518d754361858f86d8a07af53ba9af0fe635bbccb151a63"
 dependencies = [
  "ff",
- "rand_core",
+ "rand_core 0.6.4",
  "subtle",
 ]
 
@@ -725,6 +799,15 @@ dependencies = [
  "ahash 0.8.12",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.15.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
+dependencies = [
+ "foldhash",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.16.1"
@@ -785,6 +868,12 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "id-arena"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d3067d79b975e8844ca9eb072e16b31c3c1c36928edf9c6789548c524d0d954"
+
 [[package]]
 name = "ident_case"
 version = "1.0.1"
@@ -866,6 +955,12 @@ dependencies = [
  "cpufeatures",
 ]
 
+[[package]]
+name = "leb128fmt"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
+
 [[package]]
 name = "libc"
 version = "0.2.180"
@@ -878,6 +973,12 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f9fbbcab51052fe104eb5e5d351cf728d30a5be1fe14d9be8a3b097481fb97de"
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df1d3c3b53da64cf5760482273a98e575c651a67eec7f77df96b5b642de8f039"
+
 [[package]]
 name = "log"
 version = "0.4.29"
@@ -1001,6 +1102,7 @@ version = "0.0.0"
 dependencies = [
  "access-control",
  "predifi-errors",
+ "proptest",
  "pyth-sdk",
  "soroban-sdk",
 ]
@@ -1049,6 +1151,25 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "proptest"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b45fcc2344c680f5025fe57779faef368840d0bd1f42f216291f0dc4ace4744"
+dependencies = [
+ "bit-set",
+ "bit-vec",
+ "bitflags",
+ "num-traits",
+ "rand 0.9.2",
+ "rand_chacha 0.9.0",
+ "rand_xorshift",
+ "regex-syntax",
+ "rusty-fork",
+ "tempfile",
+ "unarray",
+]
+
 [[package]]
 name = "pyth-sdk"
 version = "0.3.0"
@@ -1061,6 +1182,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "quick-error"
+version = "1.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
+
 [[package]]
 name = "quote"
 version = "1.0.44"
@@ -1070,6 +1197,18 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
+[[package]]
+name = "r-efi"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
+
 [[package]]
 name = "rand"
 version = "0.8.5"
@@ -1077,8 +1216,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
 dependencies = [
  "libc",
- "rand_chacha",
- "rand_core",
+ "rand_chacha 0.3.1",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha 0.9.0",
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -1088,7 +1237,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
 dependencies = [
  "ppv-lite86",
- "rand_core",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -1097,7 +1256,25 @@ version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 dependencies = [
- "getrandom",
+ "getrandom 0.2.17",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76afc826de14238e6e8c374ddcc1fa19e374fd8dd986b0d2af0d02377261d83c"
+dependencies = [
+ "getrandom 0.3.4",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "513962919efc330f829edb2535844d1b912b0fbe2ca165d613e4e8788bb05a5a"
+dependencies = [
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -1120,6 +1297,12 @@ dependencies = [
  "syn 2.0.114",
 ]
 
+[[package]]
+name = "regex-syntax"
+version = "0.8.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
+
 [[package]]
 name = "rfc6979"
 version = "0.4.0"
@@ -1139,12 +1322,37 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "146c9e247ccc180c1f61615433868c99f3de3ae256a30a43b49f67c2d9171f34"
+dependencies = [
+ "bitflags",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
 
+[[package]]
+name = "rusty-fork"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc6bf79ff24e648f6da1f8d1f011e9cac26491b619e6b9280f2b47f1774e6ee2"
+dependencies = [
+ "fnv",
+ "quick-error",
+ "tempfile",
+ "wait-timeout",
+]
+
 [[package]]
 name = "schemars"
 version = "0.8.22"
@@ -1332,7 +1540,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
 dependencies = [
  "digest",
- "rand_core",
+ "rand_core 0.6.4",
 ]
 
 [[package]]
@@ -1369,7 +1577,7 @@ dependencies = [
  "soroban-wasmi",
  "static_assertions",
  "stellar-xdr",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1397,7 +1605,7 @@ dependencies = [
  "ed25519-dalek",
  "elliptic-curve",
  "generic-array",
- "getrandom",
+ "getrandom 0.2.17",
  "hex-literal",
  "hmac",
  "k256",
@@ -1405,8 +1613,8 @@ dependencies = [
  "num-integer",
  "num-traits",
  "p256",
- "rand",
- "rand_chacha",
+ "rand 0.8.5",
+ "rand_chacha 0.3.1",
  "sec1",
  "sha2",
  "sha3",
@@ -1415,7 +1623,7 @@ dependencies = [
  "soroban-wasmi",
  "static_assertions",
  "stellar-strkey",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1459,7 +1667,7 @@ dependencies = [
  "ctor",
  "derive_arbitrary",
  "ed25519-dalek",
- "rand",
+ "rand 0.8.5",
  "rustc_version",
  "serde",
  "serde_json",
@@ -1500,7 +1708,7 @@ dependencies = [
  "base64",
  "stellar-xdr",
  "thiserror",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1617,6 +1825,19 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0136791f7c95b1f6dd99f9cc786b91bb81c3800b639b3478e561ddb7be95e5f1"
+dependencies = [
+ "fastrand",
+ "getrandom 0.4.2",
+ "once_cell",
+ "rustix",
+ "windows-sys",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.69"
@@ -1683,12 +1904,24 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "562d481066bde0658276a35467c4af00bdc6ee726305698a55b86e61d7ad82bb"
 
+[[package]]
+name = "unarray"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eaea85b334db583fe3274d12b4cd1880032beab409c0d774be044d4480ab9a94"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
+
 [[package]]
 name = "version_check"
 version = "0.9.5"
@@ -1706,12 +1939,39 @@ dependencies = [
  "syn 2.0.114",
 ]
 
+[[package]]
+name = "wait-timeout"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09ac3b126d3914f9849036f826e054cbabdc8519970b8998ddaf3b5bd3c65f11"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "wasi"
 version = "0.11.1+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
 
+[[package]]
+name = "wasip2"
+version = "1.0.2+wasi-0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9517f9239f02c069db75e65f174b3da828fe5f5b945c4dd26bd25d89c03ebcf5"
+dependencies = [
+ "wit-bindgen",
+]
+
+[[package]]
+name = "wasip3"
+version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5428f8bf88ea5ddc08faddef2ac4a67e390b88186c703ce6dbd955e1c145aca5"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.108"
@@ -1757,6 +2017,28 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "wasm-encoder"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "990065f2fe63003fe337b932cfb5e3b80e0b4d0f5ff650e6985b1048f62c8319"
+dependencies = [
+ "leb128fmt",
+ "wasmparser 0.244.0",
+]
+
+[[package]]
+name = "wasm-metadata"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0e353e6a2fbdc176932bbaab493762eb1255a7900fe0fea1a2f96c296cc909"
+dependencies = [
+ "anyhow",
+ "indexmap 2.13.0",
+ "wasm-encoder",
+ "wasmparser 0.244.0",
+]
+
 [[package]]
 name = "wasmi_arena"
 version = "0.4.1"
@@ -1785,6 +2067,18 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "wasmparser"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47b807c72e1bac69382b3a6fb3dbe8ea4c0ed87ff5629b8685ae6b9a611028fe"
+dependencies = [
+ "bitflags",
+ "hashbrown 0.15.5",
+ "indexmap 2.13.0",
+ "semver",
+]
+
 [[package]]
 name = "wasmparser-nostd"
 version = "0.100.2"
@@ -1853,6 +2147,103 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "windows-sys"
+version = "0.61.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
+dependencies = [
+ "windows-link",
+]
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+ "wit-bindgen-rust-macro",
+]
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+ "anyhow",
+ "heck",
+ "wit-parser",
+]
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+[[package]]
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+ "anyhow",
+ "heck",
+ "indexmap 2.13.0",
+ "prettyplease",
+ "syn 2.0.114",
+ "wasm-metadata",
+ "wit-bindgen-core",
+ "wit-component",
+]
+
+[[package]]
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+ "anyhow",
+ "prettyplease",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.114",
+ "wit-bindgen-core",
+ "wit-bindgen-rust",
+]
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+ "bitflags",
+ "indexmap 2.13.0",
+ "log",
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+ "serde_json",
+ "wasm-encoder",
+ "wasm-metadata",
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+ "wit-parser",
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+ "anyhow",
+ "id-arena",
+ "indexmap 2.13.0",
+ "log",
+ "semver",
+ "serde",
+ "serde_derive",
+ "serde_json",
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 [[package]]
 name = "zerocopy"
 version = "0.8.33"
diff --git a/contract/Cargo.toml b/contract/Cargo.toml
index ebe8ed6..3450b29 100644
--- a/contract/Cargo.toml
+++ b/contract/Cargo.toml
@@ -13,6 +13,7 @@ predifi-errors  = { path = "contracts/predifi-errors" }
 access-control  = { path = "contracts/access-control" }
 # Pyth Network dependencies for price feeds
 pyth-sdk = "0.3.0"
+proptest = "1.6.0"
 
 # ── Release profile (optimised for WASM size) ──────────────────────────────────
 [profile.release]
diff --git a/contract/contracts/predifi-contract/Cargo.toml b/contract/contracts/predifi-contract/Cargo.toml
index 9db47a4..dedcfc0 100644
--- a/contract/contracts/predifi-contract/Cargo.toml
+++ b/contract/contracts/predifi-contract/Cargo.toml
@@ -22,3 +22,4 @@ pyth-sdk = { workspace = true }
 
 [dev-dependencies]
 soroban-sdk = { workspace = true, features = ["testutils"] }
+proptest    = { workspace = true }
diff --git a/contract/contracts/predifi-contract/src/lib.rs b/contract/contracts/predifi-contract/src/lib.rs
index cdf72ae..dbbfb13 100644
--- a/contract/contracts/predifi-contract/src/lib.rs
+++ b/contract/contracts/predifi-contract/src/lib.rs
@@ -1,6 +1,8 @@
 #![no_std]
 #![allow(clippy::too_many_arguments)]
 
+#[cfg(test)]
+mod payout_proptests;
 mod price_feed;
 mod price_feed_simple;
 mod safe_math;
diff --git a/contract/contracts/predifi-contract/src/payout_proptests.rs b/contract/contracts/predifi-contract/src/payout_proptests.rs
new file mode 100644
index 0000000..f6a6667
--- /dev/null
+++ b/contract/contracts/predifi-contract/src/payout_proptests.rs
@@ -0,0 +1,90 @@
+#[cfg(test)]
+extern crate std;
+#[cfg(test)]
+use crate::safe_math::{RoundingMode, SafeMath};
+#[cfg(test)]
+use proptest::prelude::*;
+#[cfg(test)]
+use std::vec::Vec;
+
+#[cfg(test)]
+proptest! {
+    #[test]
+    fn test_payout_invariants(
+        total_stake in 1..100_000_000_000_000i128, // Up to 10M tokens with 7 decimals
+        fee_bps in 0..=10_000u32,
+        winning_outcome_share_bps in 1..=10_000u32,
+    ) {
+        let fee_bps_i = fee_bps as i128;
+
+        // 1. Calculate protocol fee
+        let protocol_fee_total = SafeMath::percentage(total_stake, fee_bps_i, RoundingMode::ProtocolFavor).unwrap();
+        let payout_pool = total_stake - protocol_fee_total;
+
+        // 2. Calculate winning stake based on winning_outcome_share_bps
+        // We ensure at least 1 unit is winning stake if total_stake > 0
+        let winning_stake = (total_stake * winning_outcome_share_bps as i128) / 10_000;
+        let winning_stake = if winning_stake == 0 { 1 } else { winning_stake };
+
+        // 3. Simulate multiple winners staking on the winning outcome
+        // For simplicity in proptest, we can just check if a single user with the full winning_stake gets exactly payout_pool
+        // (Modulo rounding if winning_stake != total_stake, but here winning_stake is the total competing for payout_pool)
+
+        // If one user has the entire winning_stake:
+        let user_stake = winning_stake;
+        let winnings = SafeMath::calculate_share(user_stake, winning_stake, payout_pool).unwrap();
+
+        // Invariant: winnings + protocol_fee_total <= total_stake
+        prop_assert!(winnings + protocol_fee_total <= total_stake);
+
+        // Invariant: winnings should be equal to payout_pool if one user owns the whole winning side
+        prop_assert_eq!(winnings, payout_pool);
+    }
+
+    #[test]
+    fn test_distribution_sum_invariant(
+        total_stake in 1000..100_000_000_000_000i128,
+        fee_bps in 0..=5000u32, // Up to 50% fee
+        num_winners in 1..20usize,
+    ) {
+        let fee_bps_i = fee_bps as i128;
+        let protocol_fee_total = SafeMath::percentage(total_stake, fee_bps_i, RoundingMode::ProtocolFavor).unwrap();
+        let payout_pool = total_stake - protocol_fee_total;
+
+        // Distribute winning_stake among num_winners
+        let winning_stake = total_stake / 2; // Assume 50% of total stake is winning
+        if winning_stake == 0 { return Ok(()); }
+
+        let mut individual_stakes = Vec::new();
+        let mut remaining_winning_stake = winning_stake;
+
+        for i in 0..num_winners {
+            if i == num_winners - 1 {
+                individual_stakes.push(remaining_winning_stake);
+            } else {
+                let stake = remaining_winning_stake / 2;
+                if stake > 0 {
+                    individual_stakes.push(stake);
+                    remaining_winning_stake -= stake;
+                } else {
+                    individual_stakes.push(remaining_winning_stake);
+                    break;
+                }
+            }
+        }
+
+        let mut total_winnings = 0i128;
+        for &user_stake in individual_stakes.iter() {
+            if user_stake > 0 {
+                let winnings = SafeMath::calculate_share(user_stake, winning_stake, payout_pool).unwrap();
+                total_winnings += winnings;
+            }
+        }
+
+        // Sum of winnings + fee should be <= total_stake
+        prop_assert!(total_winnings + protocol_fee_total <= total_stake);
+
+        // The difference (dust) should be less than the number of winners
+        prop_assert!(payout_pool - total_winnings < num_winners as i128);
+    }
+}
diff --git a/contract/contracts/predifi-contract/test_output.txt b/contract/contracts/predifi-contract/test_output.txt
new file mode 100644
index 0000000..8463288
--- /dev/null
+++ b/contract/contracts/predifi-contract/test_output.txt
@@ -0,0 +1,25 @@
+warning: value assigned to `remaining_winning_stake` is never read
+  --> contracts/predifi-contract/src/payout_proptests.rs:71:21
+   |
+71 |                     remaining_winning_stake = 0;
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: `predifi-contract` (lib test) generated 1 warning
+    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.11s
+     Running unittests src/lib.rs (/home/edohwares/Desktop/Room/drips/predifi/contract/target/debug/deps/predifi_contract-70fe24d8c293d6bf)
+
+running 2 tests
+test payout_proptests::test_payout_invariants ... ok
+test payout_proptests::test_distribution_sum_invariant ... ok
+
+test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 160 filtered out; finished in 0.00s
+
+     Running tests/price_feed_integration_test.rs (/home/edohwares/Desktop/Room/drips/predifi/contract/target/debug/deps/price_feed_integration_test-3f1c7cc2c3f5f6df)
+
+running 0 tests
+
+test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out; finished in 0.00s
+