From 7b0e3f60aad516d71e55c977a833caf6d506049d Mon Sep 17 00:00:00 2001
From: Thompson <140930314+Godbrand0@users.noreply.github.com>
Date: Wed, 29 Apr 2026 06:30:29 -0400
Subject: [PATCH] test: add fuzz/property-based tests for create_stream edge
 cases

- Covered zero amount stream creation
- Covered max amount stream creation (i128::MAX)
- Covered single ledger streams
- Documented and tested truncation handling for indivisible amounts
---
 contracts/Cargo.lock                  | 439 ++++++++++++++++++++++++--
 contracts/stream_contract/Cargo.toml  |   1 +
 contracts/stream_contract/src/lib.rs  |   6 +-
 contracts/stream_contract/src/test.rs |  81 +++++
 4 files changed, 508 insertions(+), 19 deletions(-)

diff --git a/contracts/Cargo.lock b/contracts/Cargo.lock
index 855b814..527c460 100644
--- a/contracts/Cargo.lock
+++ b/contracts/Cargo.lock
@@ -23,6 +23,12 @@ 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"
@@ -147,7 +153,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94893f1e0c6eeab764ade8dc4c0db24caf4fe7cbbaafc0eba0a9030f447b5185"
 dependencies = [
  "num-traits",
- "rand",
+ "rand 0.8.5",
 ]
 
 [[package]]
@@ -180,6 +186,27 @@ 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 = "2.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4512299f36f043ab09a583e57bceb5a5aab7a73db1805848e8fef3c9e8c78b3"
+
 [[package]]
 name = "block-buffer"
 version = "0.10.4"
@@ -274,7 +301,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0dc92fb57ca44df6db8059111ab3af99a63d5d0f8375d9972e319a379c6bab76"
 dependencies = [
  "generic-array",
- "rand_core",
+ "rand_core 0.6.4",
  "subtle",
  "zeroize",
 ]
@@ -499,7 +526,7 @@ checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
 dependencies = [
  "curve25519-dalek",
  "ed25519",
- "rand_core",
+ "rand_core 0.6.4",
  "serde",
  "sha2",
  "subtle",
@@ -524,7 +551,7 @@ dependencies = [
  "ff",
  "generic-array",
  "group",
- "rand_core",
+ "rand_core 0.6.4",
  "sec1",
  "subtle",
  "zeroize",
@@ -536,6 +563,16 @@ 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"
@@ -548,13 +585,19 @@ version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ca81e6b4777c89fd810c25a4be2b1bd93ea034fbe58e6a75216a34c6b82c539b"
 
+[[package]]
+name = "fastrand"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f1f227452a390804cdb637b74a86990f2a7d7ba4b7d5693aac9b4dd6defd8d6"
+
 [[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",
 ]
 
@@ -576,6 +619,12 @@ 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"
@@ -600,6 +649,31 @@ 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"
@@ -607,7 +681,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f0f9ef7462f7c099f518d754361858f86d8a07af53ba9af0fe635bbccb151a63"
 dependencies = [
  "ff",
- "rand_core",
+ "rand_core 0.6.4",
  "subtle",
 ]
 
@@ -626,12 +700,27 @@ dependencies = [
  "ahash",
 ]
 
+[[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"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 
+[[package]]
+name = "heck"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+
 [[package]]
 name = "hex"
 version = "0.4.3"
@@ -680,6 +769,12 @@ 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"
@@ -761,6 +856,12 @@ 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 = "0.2.182"
@@ -773,6 +874,12 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b6d2cec3eae94f9f509c767b45932f1ada8350c4bdb85af2fcab4a3c14807981"
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
+
 [[package]]
 name = "log"
 version = "0.4.29"
@@ -907,6 +1014,31 @@ 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 0.9.4",
+ "rand_chacha 0.9.0",
+ "rand_xorshift",
+ "regex-syntax",
+ "rusty-fork",
+ "tempfile",
+ "unarray",
+]
+
+[[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"
@@ -916,6 +1048,18 @@ 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"
@@ -923,8 +1067,18 @@ 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 = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44c5af06bb1b7d3216d91932aed5265164bf384dc89cd6ba05cf59a35f5f76ea"
+dependencies = [
+ "rand_chacha 0.9.0",
+ "rand_core 0.9.5",
 ]
 
 [[package]]
@@ -934,7 +1088,17 @@ 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]]
@@ -943,7 +1107,25 @@ 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]]
@@ -966,6 +1148,12 @@ dependencies = [
  "syn 2.0.115",
 ]
 
+[[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"
@@ -985,12 +1173,37 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6fe4565b9518b83ef4f91bb47ce29620ca828bd32cb7e408f0062e9930ba190"
+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 = "0.9.0"
@@ -1142,7 +1355,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
 dependencies = [
  "digest",
- "rand_core",
+ "rand_core 0.6.4",
 ]
 
 [[package]]
@@ -1179,7 +1392,7 @@ dependencies = [
  "soroban-wasmi",
  "static_assertions",
  "stellar-xdr",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1207,7 +1420,7 @@ dependencies = [
  "ed25519-dalek",
  "elliptic-curve",
  "generic-array",
- "getrandom",
+ "getrandom 0.2.17",
  "hex-literal",
  "hmac",
  "k256",
@@ -1215,8 +1428,8 @@ dependencies = [
  "num-integer",
  "num-traits",
  "p256",
- "rand",
- "rand_chacha",
+ "rand 0.8.5",
+ "rand_chacha 0.3.1",
  "sec1",
  "sha2",
  "sha3",
@@ -1225,7 +1438,7 @@ dependencies = [
  "soroban-wasmi",
  "static_assertions",
  "stellar-strkey",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1268,7 +1481,7 @@ dependencies = [
  "ctor",
  "derive_arbitrary",
  "ed25519-dalek",
- "rand",
+ "rand 0.8.5",
  "rustc_version",
  "serde",
  "serde_json",
@@ -1308,7 +1521,7 @@ dependencies = [
  "base64 0.13.1",
  "stellar-xdr",
  "thiserror",
- "wasmparser",
+ "wasmparser 0.116.1",
 ]
 
 [[package]]
@@ -1393,6 +1606,7 @@ dependencies = [
 name = "stream_contract"
 version = "0.1.0"
 dependencies = [
+ "proptest",
  "soroban-sdk",
 ]
 
@@ -1430,6 +1644,19 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
+dependencies = [
+ "fastrand",
+ "getrandom 0.4.2",
+ "once_cell",
+ "rustix",
+ "windows-sys",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.69"
@@ -1487,24 +1714,63 @@ 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 = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "537dd038a89878be9b64dd4bd1b260315c1bb94f4d784956b81e27a088d9a09e"
 
+[[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"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[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 = "1.0.3+wasi-0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20064672db26d7cdc89c7798c48a0fdfac8213434a1186e5ef29fd560ae223d6"
+dependencies = [
+ "wit-bindgen 0.57.1",
+]
+
+[[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 0.51.0",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.108"
@@ -1550,6 +1816,28 @@ 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"
@@ -1578,6 +1866,18 @@ 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"
@@ -1646,6 +1946,109 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "windows-sys"
+version = "0.61.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
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 [[package]]
 name = "zerocopy"
 version = "0.8.39"
diff --git a/contracts/stream_contract/Cargo.toml b/contracts/stream_contract/Cargo.toml
index 1d1e68c..509eb20 100644
--- a/contracts/stream_contract/Cargo.toml
+++ b/contracts/stream_contract/Cargo.toml
@@ -10,4 +10,5 @@ crate-type = ["cdylib"]
 soroban-sdk = { workspace = true }
 
 [dev-dependencies]
+proptest = "1.11.0"
 soroban-sdk = { workspace = true, features = ["testutils"] }
diff --git a/contracts/stream_contract/src/lib.rs b/contracts/stream_contract/src/lib.rs
index 3d0b0ac..0287dd3 100644
--- a/contracts/stream_contract/src/lib.rs
+++ b/contracts/stream_contract/src/lib.rs
@@ -106,7 +106,11 @@ impl StreamContract {
     ///
     /// Transfers `amount` tokens from `sender` to the contract, deducts the
     /// protocol fee (if configured), and records the stream with a calculated
-    /// `rate_per_second = net_amount / duration`.
+    /// `rate_per_second = net_amount / duration`. Any remainder from the division
+    /// is truncated from `rate_per_second`. This means at exactly `start_time + duration`,
+    /// the claimable amount will be slightly less than `net_amount`. 
+    /// The remainder is only claimable if the stream runs past the initial duration,
+    /// or it is refunded to the sender if the stream is cancelled exactly at the end of the duration.
     ///
     /// Returns the new stream ID (starts at 1, increments monotonically).
     ///
diff --git a/contracts/stream_contract/src/test.rs b/contracts/stream_contract/src/test.rs
index 10181bc..480440f 100644
--- a/contracts/stream_contract/src/test.rs
+++ b/contracts/stream_contract/src/test.rs
@@ -1806,3 +1806,84 @@ fn test_fuzz_large_amount_no_overflow() {
         assert!(claimable <= *amount);
     }
 }
+
+use proptest::prelude::*;
+
+proptest! {
+    #[test]
+    fn prop_create_stream_zero_amount_returns_error(amount in 0i128..=0i128, duration in 1u64..=1000u64) {
+        let env = Env::default();
+        env.mock_all_auths();
+        let (token, _) = create_token(&env);
+        let sender = Address::generate(&env);
+        let recipient = Address::generate(&env);
+        let client = create_contract(&env);
+        
+        let result = client.try_create_stream(&sender, &recipient, &token, &amount, &duration);
+        assert_eq!(result, Err(Ok(StreamError::InvalidAmount)));
+    }
+    
+    #[test]
+    fn prop_create_stream_max_amount_no_overflow(duration in 1u64..=100_000u64) {
+        let env = Env::default();
+        env.mock_all_auths();
+        let (token, _) = create_token(&env);
+        let sender = Address::generate(&env);
+        let recipient = Address::generate(&env);
+        let amount = i128::MAX;
+        mint(&env, &token, &sender, amount);
+        let client = create_contract(&env);
+        
+        let id = client.create_stream(&sender, &recipient, &token, &amount, &duration);
+        let stream = client.get_stream(&id).unwrap();
+        assert_eq!(stream.deposited_amount, amount);
+        
+        env.ledger().with_mut(|l| l.timestamp += 1);
+        let claimable = client.get_claimable_amount(&id).unwrap();
+        assert!(claimable >= 0);
+    }
+    
+    #[test]
+    fn prop_single_ledger_stream(amount in 1i128..=1_000_000_000i128) {
+        let env = Env::default();
+        env.mock_all_auths();
+        let (token, _) = create_token(&env);
+        let sender = Address::generate(&env);
+        let recipient = Address::generate(&env);
+        mint(&env, &token, &sender, amount);
+        let client = create_contract(&env);
+        
+        let duration = 1;
+        let id = client.create_stream(&sender, &recipient, &token, &amount, &duration);
+        
+        env.ledger().with_mut(|l| l.timestamp += 1);
+        let claimable = client.get_claimable_amount(&id).unwrap();
+        assert_eq!(claimable, amount);
+    }
+    
+    #[test]
+    fn prop_amount_not_perfectly_divisible(amount in 10i128..=10_000i128, duration in 3u64..=1000u64) {
+        prop_assume!(amount % (duration as i128) != 0);
+        let env = Env::default();
+        env.mock_all_auths();
+        let (token, _) = create_token(&env);
+        let sender = Address::generate(&env);
+        let recipient = Address::generate(&env);
+        mint(&env, &token, &sender, amount);
+        let client = create_contract(&env);
+        
+        let id = client.create_stream(&sender, &recipient, &token, &amount, &duration);
+        
+        env.ledger().with_mut(|l| l.timestamp += duration);
+        let claimable_at_duration = client.get_claimable_amount(&id).unwrap();
+        let rate = amount / (duration as i128);
+        assert_eq!(claimable_at_duration, rate * (duration as i128));
+        
+        let sender_balance_before = token::Client::new(&env, &token).balance(&sender);
+        client.cancel_stream(&sender, &id);
+        let sender_balance_after = token::Client::new(&env, &token).balance(&sender);
+        
+        let remainder = amount % (duration as i128);
+        assert_eq!(sender_balance_after - sender_balance_before, remainder);
+    }
+}