// from https://github.com/catchorg/Catch2/blob/devel/examples/010-TestCase.cpp
// 010-TestCase.cpp

#include <catch2/catch_test_macros.hpp>
#include "lmath/factorial.h"

/*
 * n	n!
 * 0	1
 * 1	1
 * 2	2
 * 3	6
 * 4	24
 * 5	120
 * 6	720
 * 7	5,040
 * 8	40,320
 * 9	362,880
 * 10	3,628,800
 * 11	39,916,800
 * 12	479,001,600
 * 13	6,227,020,800
 * 14	87,178,291,200
 * 15	1,307,674,368,000
 * 16	20,922,789,888,000
 * 17	355,687,428,096,000
 * 18	6,402,373,705,728,000
 * 19	121,645,100,408,832,000 <<--- limit of uintmax_t
 * 20	2,432,902,008,176,640,000
 * 21	51,090,942,171,709,440,000
 * 22	1,124,000,727,777,607,680,000
 * 23	25,852,016,738,884,976,640,000
 * 24	620,448,401,733,239,439,360,000
 * 25	15,511,210,043,330,985,984,000,000
*/

Factorial f;

TEST_CASE( "Factorial of 0 is 1 ", "[factorial]" ) {
    REQUIRE( f.fact(0) == 1 );
}

TEST_CASE( "Factorials of 1 and higher", "[factorial]" ) {
    REQUIRE( f.fact(1) == 1 );
    REQUIRE( f.fact(2) == 2 );
    REQUIRE( f.fact(10) == 3'628'800 );
    // uncomment to see what a fail looks like:
    //REQUIRE( f.fact(20) == 2'432'902'008'176'640'000 );
}