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Merged
merged 1 commit into from
Jan 11, 2017
Merged

Update Luhn tests #275

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32 changes: 15 additions & 17 deletions exercises/luhn/Example.fs
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Original file line number Diff line number Diff line change
@@ -1,29 +1,27 @@
module Luhn

let digit c = (int)c - (int)'0'
let digits number = number.ToString() |> Seq.map digit

let addend index digit =
let private digit c = (int)c - (int)'0'
let private digits number = number.ToString() |> Seq.map digit

let private addend index digit =
if (index % 2 = 0) then digit else
if (digit >= 5) then digit * 2 - 9
else digit * 2

let checkDigit (number:int64) = number % 10L

let addends (number:int64) =
number
|> digits
let private addends number =
number
|> List.ofSeq
|> List.rev
|> List.mapi addend
|> List.rev

let checksum (number:int64) = (number |> addends |> List.sum) % 10

let valid (number:int64) = checksum number = 0

let create (target:int64) =
let targetNumber = target * 10L
let private checksum number = (number |> digits |> addends |> List.sum) % 10

if valid targetNumber then targetNumber
else targetNumber + 10L - (int64)(checksum targetNumber)
let valid (number : string) =
let noSpaces = number.Replace(" ", "")
match Seq.length noSpaces with
| 0 | 1 -> false
| _ ->
match Seq.forall (fun c -> c >= '0' && c <= '9') noSpaces with
| false -> false
| true -> checksum noSpaces = 0
46 changes: 8 additions & 38 deletions exercises/luhn/LuhnTest.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,41 +3,11 @@ module LuhnTest
open NUnit.Framework
open Luhn

[<Test>]
let ``Check digit is the rightmost digit`` () =
Assert.That(checkDigit 34567L, Is.EqualTo 7)

[<Test>]
[<Ignore("Remove to run test")>]
let ``Addends doubles every other number from the right`` () =
Assert.That(addends 12121L, Is.EqualTo [1; 4; 1; 4; 1])

[<Test>]
[<Ignore("Remove to run test")>]
let ``Addends subtracts 9 when doubled number is more than 9`` () =
Assert.That(addends 8631L, Is.EqualTo [7; 6; 6; 1])

[<TestCase(4913, ExpectedResult = 2)>]
[<TestCase(201773, ExpectedResult = 1)>]
let ``Checksum adds addends together`` (number) =
checksum number

[<TestCase(738, ExpectedResult = false)>]
[<TestCase(8739567, ExpectedResult = true)>]
let ``Number is valid when checksum mod 10 is zero`` (number) =
valid number

[<Test>]
[<Ignore("Remove to run test")>]
let ``Luhn can create simple numbers with valid check digit`` () =
Assert.That(create 123L, Is.EqualTo(1230))

[<Test>]
[<Ignore("Remove to run test")>]
let ``Luhn can create larger numbers with valid check digit`` () =
Assert.That(create 873956L, Is.EqualTo(8739567))

[<Test>]
[<Ignore("Remove to run test")>]
let ``Luhn can create huge numbers with valid check digit`` () =
Assert.That(create 837263756L, Is.EqualTo(8372637564L))
[<TestCase("1", ExpectedResult = false)>] // single digit strings can not be valid
[<TestCase("0", ExpectedResult = false, Ignore = "Remove to run test")>] // a single zero is invalid
[<TestCase("046 454 286", ExpectedResult = true, Ignore = "Remove to run test")>] // valid Canadian SIN
[<TestCase("046 454 287", ExpectedResult = false, Ignore = "Remove to run test")>] // invalid Canadian SIN
[<TestCase("8273 1232 7352 0569", ExpectedResult = false, Ignore = "Remove to run test")>] // invalid credit card
[<TestCase("827a 1232 7352 0569", ExpectedResult = false, Ignore = "Remove to run test")>] // strings that contain non-digits are not valid
let ``Validate checksum`` number =
valid number