From a7a202305dadb1c67dea34a313d147bd5558930c Mon Sep 17 00:00:00 2001
From: Jess52487 <Jessysam52487@gmail.com>
Date: Wed, 24 Jun 2026 12:29:04 +0100
Subject: [PATCH] feat(soroban): implement repayment contract and verify unit
 tests

---
 .cargo/config.toml                            |    5 +
 .gitignore                                    |    4 +
 Cargo.lock                                    | 1752 +++++++++++++++++
 Cargo.toml                                    |   20 +
 contracts/repayment/Cargo.toml                |   15 +
 contracts/repayment/src/lib.rs                |  322 +++
 .../test_initialization_and_assignment.1.json |  235 +++
 .../test/test_overpayment_behavior.1.json     |  295 +++
 .../test/test_repayments.1.json               |  417 ++++
 .../test_unauthorized_assignment_fails.1.json |   90 +
 .../test_unauthorized_caller_rejected.1.json  |  235 +++
 .../test_unauthorized_repayment_fails.1.json  |   76 +
 12 files changed, 3466 insertions(+)
 create mode 100644 .cargo/config.toml
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 contracts/repayment/Cargo.toml
 create mode 100644 contracts/repayment/src/lib.rs
 create mode 100644 contracts/repayment/test_snapshots/test/test_initialization_and_assignment.1.json
 create mode 100644 contracts/repayment/test_snapshots/test/test_overpayment_behavior.1.json
 create mode 100644 contracts/repayment/test_snapshots/test/test_repayments.1.json
 create mode 100644 contracts/repayment/test_snapshots/test/test_unauthorized_assignment_fails.1.json
 create mode 100644 contracts/repayment/test_snapshots/test/test_unauthorized_caller_rejected.1.json
 create mode 100644 contracts/repayment/test_snapshots/test/test_unauthorized_repayment_fails.1.json

diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..dec05f1
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,5 @@
+[source.crates-io]
+replace-with = 'rsproxy-sparse'
+
+[source.rsproxy-sparse]
+registry = "sparse+https://rsproxy.cn/index/"
diff --git a/.gitignore b/.gitignore
index 0742840..7b291ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,3 +26,7 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# rust
+/target
+
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..234395e
--- /dev/null
+++ b/Cargo.lock
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+soroban-sdk = { workspace = true }
+
+[dev-dependencies]
+soroban-sdk = { workspace = true, features = ["testutils"] }
diff --git a/contracts/repayment/src/lib.rs b/contracts/repayment/src/lib.rs
new file mode 100644
index 0000000..be300ca
--- /dev/null
+++ b/contracts/repayment/src/lib.rs
@@ -0,0 +1,322 @@
+#![no_std]
+use soroban_sdk::{
+    contract, contracterror, contractimpl, contracttype, Address, Env,
+};
+
+#[contract]
+pub struct RepaymentContract;
+
+#[contracttype]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct RepaymentState {
+    pub pool_or_vehicle: Address,
+    pub total_owed: i128,
+    pub total_repaid: i128,
+    pub active: bool,
+}
+
+#[contracttype]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct RepaymentSummary {
+    pub pool_or_vehicle: Address,
+    pub total_owed: i128,
+    pub total_repaid: i128,
+    pub outstanding_balance: i128,
+    pub overpaid_amount: i128,
+    pub active: bool,
+}
+
+#[contracttype]
+#[derive(Clone)]
+pub enum DataKey {
+    Admin,
+    DriverState(Address),
+}
+
+#[contracterror]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[repr(u32)]
+pub enum Error {
+    NotInitialized = 1,
+    AlreadyInitialized = 2,
+    Unauthorized = 3,
+    NoActiveContract = 4,
+    InvalidAmount = 5,
+}
+
+#[contractimpl]
+impl RepaymentContract {
+    /// Initialize the contract and set the administrator.
+    pub fn initialize(env: Env, admin: Address) -> Result<(), Error> {
+        if env.storage().instance().has(&DataKey::Admin) {
+            return Err(Error::AlreadyInitialized);
+        }
+        env.storage().instance().set(&DataKey::Admin, &admin);
+        Ok(())
+    }
+
+    /// Admin assigns a driver to a pool or vehicle with a specified total owed amount.
+    pub fn assign_driver(
+        env: Env,
+        driver: Address,
+        pool_or_vehicle: Address,
+        total_owed: i128,
+    ) -> Result<(), Error> {
+        let admin = env
+            .storage()
+            .instance()
+            .get::<DataKey, Address>(&DataKey::Admin)
+            .ok_or(Error::NotInitialized)?;
+        
+        admin.require_auth();
+
+        if total_owed <= 0 {
+            return Err(Error::InvalidAmount);
+        }
+
+        let state = RepaymentState {
+            pool_or_vehicle,
+            total_owed,
+            total_repaid: 0,
+            active: true,
+        };
+
+        env.storage()
+            .persistent()
+            .set(&DataKey::DriverState(driver), &state);
+
+        Ok(())
+    }
+
+    /// Record a repayment amount for an active driver contract.
+    /// Caller must be either the admin or the driver themselves.
+    pub fn record_repayment(
+        env: Env,
+        caller: Address,
+        driver: Address,
+        amount: i128,
+    ) -> Result<RepaymentSummary, Error> {
+        caller.require_auth();
+
+        let admin = env
+            .storage()
+            .instance()
+            .get::<DataKey, Address>(&DataKey::Admin)
+            .ok_or(Error::NotInitialized)?;
+
+        if caller != admin && caller != driver {
+            return Err(Error::Unauthorized);
+        }
+
+        if amount <= 0 {
+            return Err(Error::InvalidAmount);
+        }
+
+        let key = DataKey::DriverState(driver.clone());
+        let mut state = env
+            .storage()
+            .persistent()
+            .get::<DataKey, RepaymentState>(&key)
+            .ok_or(Error::NoActiveContract)?;
+
+        if !state.active {
+            return Err(Error::NoActiveContract);
+        }
+
+        state.total_repaid += amount;
+
+        env.storage().persistent().set(&key, &state);
+
+        // Compute dynamic summary
+        let outstanding_balance = if state.total_repaid >= state.total_owed {
+            0
+        } else {
+            state.total_owed - state.total_repaid
+        };
+
+        let overpaid_amount = if state.total_repaid > state.total_owed {
+            state.total_repaid - state.total_owed
+        } else {
+            0
+        };
+
+        Ok(RepaymentSummary {
+            pool_or_vehicle: state.pool_or_vehicle,
+            total_owed: state.total_owed,
+            total_repaid: state.total_repaid,
+            outstanding_balance,
+            overpaid_amount,
+            active: state.active,
+        })
+    }
+
+    /// Query the current repayment summary for a driver.
+    pub fn get_summary(env: Env, driver: Address) -> Result<RepaymentSummary, Error> {
+        let key = DataKey::DriverState(driver);
+        let state = env
+            .storage()
+            .persistent()
+            .get::<DataKey, RepaymentState>(&key)
+            .ok_or(Error::NoActiveContract)?;
+
+        let outstanding_balance = if state.total_repaid >= state.total_owed {
+            0
+        } else {
+            state.total_owed - state.total_repaid
+        };
+
+        let overpaid_amount = if state.total_repaid > state.total_owed {
+            state.total_repaid - state.total_owed
+        } else {
+            0
+        };
+
+        Ok(RepaymentSummary {
+            pool_or_vehicle: state.pool_or_vehicle,
+            total_owed: state.total_owed,
+            total_repaid: state.total_repaid,
+            outstanding_balance,
+            overpaid_amount,
+            active: state.active,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use soroban_sdk::testutils::Address as _;
+
+    #[test]
+    fn test_initialization_and_assignment() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let admin = Address::generate(&env);
+        let driver = Address::generate(&env);
+        let vehicle = Address::generate(&env);
+
+        client.initialize(&admin);
+
+        // Assign driver
+        client.assign_driver(&driver, &vehicle, &1000);
+
+        // Verify assignment
+        let summary = client.get_summary(&driver);
+        assert_eq!(summary.pool_or_vehicle, vehicle);
+        assert_eq!(summary.total_owed, 1000);
+        assert_eq!(summary.total_repaid, 0);
+        assert_eq!(summary.outstanding_balance, 1000);
+        assert_eq!(summary.overpaid_amount, 0);
+        assert!(summary.active);
+    }
+
+    #[test]
+    fn test_repayments() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let admin = Address::generate(&env);
+        let driver = Address::generate(&env);
+        let vehicle = Address::generate(&env);
+
+        client.initialize(&admin);
+        client.assign_driver(&driver, &vehicle, &1000);
+
+        // First repayment
+        let summary = client.record_repayment(&driver, &driver, &300);
+        assert_eq!(summary.total_repaid, 300);
+        assert_eq!(summary.outstanding_balance, 700);
+
+        // Multiple repayments
+        let summary = client.record_repayment(&driver, &driver, &400);
+        assert_eq!(summary.total_repaid, 700);
+        assert_eq!(summary.outstanding_balance, 300);
+
+        // Full repayment
+        let summary = client.record_repayment(&driver, &driver, &300);
+        assert_eq!(summary.total_repaid, 1000);
+        assert_eq!(summary.outstanding_balance, 0);
+        assert_eq!(summary.overpaid_amount, 0);
+    }
+
+    #[test]
+    fn test_overpayment_behavior() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let admin = Address::generate(&env);
+        let driver = Address::generate(&env);
+        let vehicle = Address::generate(&env);
+
+        client.initialize(&admin);
+        client.assign_driver(&driver, &vehicle, &1000);
+
+        // Record overpayment
+        let summary = client.record_repayment(&driver, &driver, &1200);
+        assert_eq!(summary.total_repaid, 1200);
+        assert_eq!(summary.outstanding_balance, 0);
+        assert_eq!(summary.overpaid_amount, 200);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_unauthorized_repayment_fails() {
+        let env = Env::default();
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let driver = Address::generate(&env);
+
+        // Calling record_repayment without mock_all_auths will panic on driver.require_auth()
+        let _ = client.record_repayment(&driver, &driver, &100);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_unauthorized_assignment_fails() {
+        let env = Env::default();
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let admin = Address::generate(&env);
+        let driver = Address::generate(&env);
+        let vehicle = Address::generate(&env);
+
+        client.initialize(&admin);
+
+        // Attacker attempts to assign driver (no mock_all_auths, will fail admin auth verify)
+        client.assign_driver(&driver, &vehicle, &1000);
+    }
+
+    #[test]
+    fn test_unauthorized_caller_rejected() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let contract_id = env.register(RepaymentContract, ());
+        let client = RepaymentContractClient::new(&env, &contract_id);
+
+        let admin = Address::generate(&env);
+        let driver = Address::generate(&env);
+        let vehicle = Address::generate(&env);
+        let attacker = Address::generate(&env);
+
+        client.initialize(&admin);
+        client.assign_driver(&driver, &vehicle, &1000);
+
+        // Attacker attempts to record repayment for driver (mock_all_auths is enabled so require_auth passes,
+        // but contract logic rejects caller because caller != admin && caller != driver)
+        let result = client.try_record_repayment(&attacker, &driver, &200);
+        assert_eq!(result.unwrap_err().unwrap(), Error::Unauthorized);
+    }
+}
diff --git a/contracts/repayment/test_snapshots/test/test_initialization_and_assignment.1.json b/contracts/repayment/test_snapshots/test/test_initialization_and_assignment.1.json
new file mode 100644
index 0000000..c0a6589
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_initialization_and_assignment.1.json
@@ -0,0 +1,235 @@
+{
+  "generators": {
+    "address": 4,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    [],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "assign_driver",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 1000
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    []
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": {
+              "vec": [
+                {
+                  "symbol": "DriverState"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                }
+              ]
+            },
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": {
+                  "vec": [
+                    {
+                      "symbol": "DriverState"
+                    },
+                    {
+                      "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                    }
+                  ]
+                },
+                "durability": "persistent",
+                "val": {
+                  "map": [
+                    {
+                      "key": {
+                        "symbol": "active"
+                      },
+                      "val": {
+                        "bool": true
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "pool_or_vehicle"
+                      },
+                      "val": {
+                        "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_owed"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1000
+                        }
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_repaid"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 0
+                        }
+                      }
+                    }
+                  ]
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": [
+                      {
+                        "key": {
+                          "vec": [
+                            {
+                              "symbol": "Admin"
+                            }
+                          ]
+                        },
+                        "val": {
+                          "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4"
+                        }
+                      }
+                    ]
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 801925984706572462
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 801925984706572462
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file
diff --git a/contracts/repayment/test_snapshots/test/test_overpayment_behavior.1.json b/contracts/repayment/test_snapshots/test/test_overpayment_behavior.1.json
new file mode 100644
index 0000000..9965a3e
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_overpayment_behavior.1.json
@@ -0,0 +1,295 @@
+{
+  "generators": {
+    "address": 4,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    [],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "assign_driver",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 1000
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "record_repayment",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 1200
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ]
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": {
+              "vec": [
+                {
+                  "symbol": "DriverState"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                }
+              ]
+            },
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": {
+                  "vec": [
+                    {
+                      "symbol": "DriverState"
+                    },
+                    {
+                      "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                    }
+                  ]
+                },
+                "durability": "persistent",
+                "val": {
+                  "map": [
+                    {
+                      "key": {
+                        "symbol": "active"
+                      },
+                      "val": {
+                        "bool": true
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "pool_or_vehicle"
+                      },
+                      "val": {
+                        "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_owed"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1000
+                        }
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_repaid"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1200
+                        }
+                      }
+                    }
+                  ]
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": [
+                      {
+                        "key": {
+                          "vec": [
+                            {
+                              "symbol": "Admin"
+                            }
+                          ]
+                        },
+                        "val": {
+                          "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4"
+                        }
+                      }
+                    ]
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 801925984706572462
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 801925984706572462
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 5541220902715666415
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 5541220902715666415
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file
diff --git a/contracts/repayment/test_snapshots/test/test_repayments.1.json b/contracts/repayment/test_snapshots/test/test_repayments.1.json
new file mode 100644
index 0000000..ea0801f
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_repayments.1.json
@@ -0,0 +1,417 @@
+{
+  "generators": {
+    "address": 4,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    [],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "assign_driver",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 1000
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "record_repayment",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 300
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "record_repayment",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 400
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "record_repayment",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 300
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ]
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": {
+              "vec": [
+                {
+                  "symbol": "DriverState"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                }
+              ]
+            },
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": {
+                  "vec": [
+                    {
+                      "symbol": "DriverState"
+                    },
+                    {
+                      "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                    }
+                  ]
+                },
+                "durability": "persistent",
+                "val": {
+                  "map": [
+                    {
+                      "key": {
+                        "symbol": "active"
+                      },
+                      "val": {
+                        "bool": true
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "pool_or_vehicle"
+                      },
+                      "val": {
+                        "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_owed"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1000
+                        }
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_repaid"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1000
+                        }
+                      }
+                    }
+                  ]
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": [
+                      {
+                        "key": {
+                          "vec": [
+                            {
+                              "symbol": "Admin"
+                            }
+                          ]
+                        },
+                        "val": {
+                          "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4"
+                        }
+                      }
+                    ]
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 801925984706572462
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 801925984706572462
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 1033654523790656264
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 1033654523790656264
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 4837995959683129791
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 4837995959683129791
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 5541220902715666415
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 5541220902715666415
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file
diff --git a/contracts/repayment/test_snapshots/test/test_unauthorized_assignment_fails.1.json b/contracts/repayment/test_snapshots/test/test_unauthorized_assignment_fails.1.json
new file mode 100644
index 0000000..452da52
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_unauthorized_assignment_fails.1.json
@@ -0,0 +1,90 @@
+{
+  "generators": {
+    "address": 4,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    [],
+    []
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": [
+                      {
+                        "key": {
+                          "vec": [
+                            {
+                              "symbol": "Admin"
+                            }
+                          ]
+                        },
+                        "val": {
+                          "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4"
+                        }
+                      }
+                    ]
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file
diff --git a/contracts/repayment/test_snapshots/test/test_unauthorized_caller_rejected.1.json b/contracts/repayment/test_snapshots/test/test_unauthorized_caller_rejected.1.json
new file mode 100644
index 0000000..7b7b6ac
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_unauthorized_caller_rejected.1.json
@@ -0,0 +1,235 @@
+{
+  "generators": {
+    "address": 5,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    [],
+    [
+      [
+        "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+        {
+          "function": {
+            "contract_fn": {
+              "contract_address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+              "function_name": "assign_driver",
+              "args": [
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                },
+                {
+                  "i128": {
+                    "hi": 0,
+                    "lo": 1000
+                  }
+                }
+              ]
+            }
+          },
+          "sub_invocations": []
+        }
+      ]
+    ],
+    []
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": {
+              "vec": [
+                {
+                  "symbol": "DriverState"
+                },
+                {
+                  "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                }
+              ]
+            },
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": {
+                  "vec": [
+                    {
+                      "symbol": "DriverState"
+                    },
+                    {
+                      "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHK3M"
+                    }
+                  ]
+                },
+                "durability": "persistent",
+                "val": {
+                  "map": [
+                    {
+                      "key": {
+                        "symbol": "active"
+                      },
+                      "val": {
+                        "bool": true
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "pool_or_vehicle"
+                      },
+                      "val": {
+                        "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAITA4"
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_owed"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 1000
+                        }
+                      }
+                    },
+                    {
+                      "key": {
+                        "symbol": "total_repaid"
+                      },
+                      "val": {
+                        "i128": {
+                          "hi": 0,
+                          "lo": 0
+                        }
+                      }
+                    }
+                  ]
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": [
+                      {
+                        "key": {
+                          "vec": [
+                            {
+                              "symbol": "Admin"
+                            }
+                          ]
+                        },
+                        "val": {
+                          "address": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4"
+                        }
+                      }
+                    ]
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+            "key": {
+              "ledger_key_nonce": {
+                "nonce": 801925984706572462
+              }
+            },
+            "durability": "temporary"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFCT4",
+                "key": {
+                  "ledger_key_nonce": {
+                    "nonce": 801925984706572462
+                  }
+                },
+                "durability": "temporary",
+                "val": "void"
+              }
+            },
+            "ext": "v0"
+          },
+          6311999
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file
diff --git a/contracts/repayment/test_snapshots/test/test_unauthorized_repayment_fails.1.json b/contracts/repayment/test_snapshots/test/test_unauthorized_repayment_fails.1.json
new file mode 100644
index 0000000..5655749
--- /dev/null
+++ b/contracts/repayment/test_snapshots/test/test_unauthorized_repayment_fails.1.json
@@ -0,0 +1,76 @@
+{
+  "generators": {
+    "address": 2,
+    "nonce": 0
+  },
+  "auth": [
+    [],
+    []
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": null
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}
\ No newline at end of file