[
 {
  "name": "pro rata after 90 of 365 days: 600.00 keeps 147.95 and returns 452.05",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "pro-rata",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 90,
   "totalDays": 365,
   "retained": {
    "minor": 14795,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 45205,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "short period on the last day of the 3-month band keeps 40%",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 90,
   "totalDays": 365,
   "retained": {
    "minor": 24000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 36000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "one day into the 4th month moves to the 50% band",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-02",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 91,
   "totalDays": 365,
   "retained": {
    "minor": 30000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 30000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "four days in: the one-week band keeps 10%",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-01-05",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 4,
   "totalDays": 365,
   "retained": {
    "minor": 6000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 54000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "exactly 8 months keeps 80%",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-09-01",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 243,
   "totalDays": 365,
   "retained": {
    "minor": 48000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 12000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "longer than every band keeps the whole premium",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-09-02",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 244,
   "totalDays": 365,
   "retained": {
    "minor": 60000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 0,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "pro rata cancelled on the inception date returns everything",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-01-01",
   "pro-rata",
   [],
   null
  ],
  "expect": {
   "daysInForce": 0,
   "totalDays": 365,
   "retained": {
    "minor": 0,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 60000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "pro rata cancelled on the expiry date returns nothing",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2027-01-01",
   "pro-rata",
   [],
   null
  ],
  "expect": {
   "daysInForce": 365,
   "totalDays": 365,
   "retained": {
    "minor": 60000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 0,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "a minimum retained premium of 75.00 beats 23.01 pro rata",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-01-15",
   "pro-rata",
   [],
   {
    "minor": 7500,
    "currency": "GBP"
   }
  ],
  "expect": {
   "daysInForce": 14,
   "totalDays": 365,
   "retained": {
    "minor": 7500,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 52500,
    "currency": "GBP"
   },
   "minimumApplied": true
  }
 },
 {
  "name": "the minimum is capped at the premium: nothing more than was paid is kept",
  "args": [
   {
    "minor": 5000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-01-11",
   "pro-rata",
   [],
   {
    "minor": 7500,
    "currency": "GBP"
   }
  ],
  "expect": {
   "daysInForce": 10,
   "totalDays": 365,
   "retained": {
    "minor": 5000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 0,
    "currency": "GBP"
   },
   "minimumApplied": true
  }
 },
 {
  "name": "a minimum below the scale's figure changes nothing",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   {
    "minor": 7500,
    "currency": "GBP"
   }
  ],
  "expect": {
   "daysInForce": 90,
   "totalDays": 365,
   "retained": {
    "minor": 24000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 36000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "20% of 333.33 is 66.666, kept as 66.67",
  "args": [
   {
    "minor": 33333,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-01-20",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 19,
   "totalDays": 365,
   "retained": {
    "minor": 6667,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 26666,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "a month is a calendar month: 30 days from 31 January passes 28 February, so the 2-month band",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-31",
   "2027-01-31",
   "2026-03-02",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 30,
   "totalDays": 365,
   "retained": {
    "minor": 18000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 42000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "28 February is exactly one month from 31 January",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-31",
   "2027-01-31",
   "2026-02-28",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 28,
   "totalDays": 365,
   "retained": {
    "minor": 12000,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 48000,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "a leap-year policy has 366 days: 274 of them keep 274.00 of 366.00",
  "args": [
   {
    "minor": 36600,
    "currency": "GBP"
   },
   "2027-06-01",
   "2028-06-01",
   "2028-03-01",
   "pro-rata",
   [],
   null
  ],
  "expect": {
   "daysInForce": 274,
   "totalDays": 366,
   "retained": {
    "minor": 27400,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 9200,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "a zero premium returns zero",
  "args": [
   {
    "minor": 0,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 7,
     "unit": "days",
     "retainedBasisPoints": 1000
    },
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 2000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 3,
     "unit": "months",
     "retainedBasisPoints": 4000
    },
    {
     "upTo": 4,
     "unit": "months",
     "retainedBasisPoints": 5000
    },
    {
     "upTo": 6,
     "unit": "months",
     "retainedBasisPoints": 7000
    },
    {
     "upTo": 8,
     "unit": "months",
     "retainedBasisPoints": 8000
    }
   ],
   null
  ],
  "expect": {
   "daysInForce": 90,
   "totalDays": 365,
   "retained": {
    "minor": 0,
    "currency": "GBP"
   },
   "returnPremium": {
    "minor": 0,
    "currency": "GBP"
   },
   "minimumApplied": false
  }
 },
 {
  "name": "cancelling after expiry is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2027-01-02",
   "pro-rata",
   [],
   null
  ],
  "expectError": "cancellationDate must be from inceptionDate to expiryDate"
 },
 {
  "name": "cancelling before inception is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2025-12-31",
   "pro-rata",
   [],
   null
  ],
  "expectError": "cancellationDate must be from inceptionDate to expiryDate"
 },
 {
  "name": "expiry must be after inception",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2026-01-01",
   "2026-01-01",
   "pro-rata",
   [],
   null
  ],
  "expectError": "expiryDate must be after inceptionDate"
 },
 {
  "name": "short period without a scale is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [],
   null
  ],
  "expectError": "a short-period cancellation needs a scale"
 },
 {
  "name": "a share above 100% is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 10001
    }
   ],
   null
  ],
  "expectError": "retainedBasisPoints must be from 0 to 10000"
 },
 {
  "name": "a scale that keeps less for longer is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 1,
     "unit": "months",
     "retainedBasisPoints": 3000
    },
    {
     "upTo": 2,
     "unit": "months",
     "retainedBasisPoints": 2000
    }
   ],
   null
  ],
  "expectError": "must not keep less for a longer period"
 },
 {
  "name": "a fractional upTo is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "short-period",
   [
    {
     "upTo": 1.5,
     "unit": "months",
     "retainedBasisPoints": 3000
    }
   ],
   null
  ],
  "expectError": "upTo must be a whole number"
 },
 {
  "name": "a negative premium is refused",
  "args": [
   {
    "minor": -100,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "pro-rata",
   [],
   null
  ],
  "expectError": "premium must not be negative"
 },
 {
  "name": "a minimum in another currency is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "pro-rata",
   [],
   {
    "minor": 7500,
    "currency": "EUR"
   }
  ],
  "expectError": "currency mismatch"
 },
 {
  "name": "an unknown basis is refused",
  "args": [
   {
    "minor": 60000,
    "currency": "GBP"
   },
   "2026-01-01",
   "2027-01-01",
   "2026-04-01",
   "flat",
   [],
   null
  ],
  "expectError": "unknown basis"
 }
]