using NUnit.Framework ;

//  No data providers as TestNG has.

[ TestFixture ]
public class Factorial_Test {
  private ulong[,] data = {
    { 0 , 1 } ,
    { 1 , 1 } , 
    { 2 , 2 } ,
    { 3 , 6 } ,
    { 4 , 24 } ,
    { 5 , 120 } ,
    { 6 , 720 } ,
    { 7 , 5040 } ,
    { 8 , 40320 } ,
    { 9 , 362880 } ,
    { 10 , 3628800 } ,
    { 11 , 39916800 } ,
    { 12 , 479001600 } ,
    { 13 , 6227020800l } ,
    { 14 , 87178291200l } ,
    { 20 , 2432902008176640000l } ,
    //{ 30 , 265252859812191058636308480000000l } ,
    //{ 40 , 815915283247897734345611269596115894272000000000l }
  } ;
  private const int dataCount = 16 ;
  [ Test ]
  public void correctIterative ( ) {
    for ( int i = 0 ; i < dataCount ; ++i ) { Assert.AreEqual ( data[i,1] , Factorial.iterative ( data[i,0] ) ) ; }
  }
  [ Test ]
  public void correctRecursive ( ) {
    for ( int i = 0 ; i < dataCount ; ++i ) { Assert.AreEqual ( data[i,1] , Factorial.recursive ( data[i,0] ) ) ; }
  }
  [ Test ]
  public void correctTailRecursive ( ) {
    for ( int i = 0 ; i < dataCount ; ++i ) { Assert.AreEqual ( data[i,1] , Factorial.tailRecursive ( data[i,0] ) ) ; }
  }

  //  Negative values are just very big numbers when cast to a ulong, so testing is not sensible. 

  //[ Test ] 
  public void negativeIterative ( ) {
    for ( int i = -20 ; i < 0 ; ++i ) { Factorial.iterative ( (ulong) i ) ; }
  }
  //[ Test ] 
  public void negativeRecursive ( ) {
    for ( int i = -20 ; i < 0 ; ++i ) { Factorial.recursive ( (ulong) i ) ; }
  }
  //[ Test ] 
  public void negativeTailRecursive ( ) {
    for ( int i = -20 ; i < 0 ; ++i ) { Factorial.tailRecursive ( (ulong) i ) ; }
  }
  //  Dummy main to keep the compiler from issuing an error.
  public static int Main ( string[] args ) { return 0 ; }
}