JS test suite is failing

[strugee]

I see test suite failures locally:

% npm test

> cassis@0.1.0 test /home/alex/Development/cassis
> tape js-tests/*.js | tap-spec

   { auto_link: [Function: auto_link],
     num_to_sxg: [Function: num_to_sxg],
     sxg_to_num: [Function: sxg_to_num] }

  auto_link

    ✓ noop on strings without links
    ✓ auto_link simple .com links
    ✓ auto_link simple .edu links
    ✓ auto_link simple .io links

  num_to_sxg

    ✓ 1
    ✓ 100 to 1f
    ✓ 2^32 + 1
    ✓ 2^35
    ✗ 2^63
     ---
       operator: equal
       expected: 'FFD_YXvLFW8'
       actual:   'FFD_YXvLFU8'
       at: Test.<anonymous> (/home/alex/Development/cassis/js-tests/new_base_60-test.js:12:20)
     ...
    ✗ 2^65
     ---
       operator: equal
       expected: '110uJA7gM20Y'
       actual:   '110uJA7gM2sY'
       at: Test.<anonymous> (/home/alex/Development/cassis/js-tests/new_base_60-test.js:12:20)
     ...

  sxg_to_num

    ✓ 1
    ✓ 1f to 100
    ✓ 2^32 + 1
    ✓ 2^32 + 1
    ✗ 2^63
     ---
       operator: equal
       expected: '9223372036854775808'
       actual:   '9223372036854776000'
       at: Test.<anonymous> (/home/alex/Development/cassis/js-tests/new_base_60-test.js:19:20)
     ...
    ✗ 2^65
     ---
       operator: equal
       expected: '36893488147419103232'
       actual:   '36893488147419103000'
       at: Test.<anonymous> (/home/alex/Development/cassis/js-tests/new_base_60-test.js:19:20)
     ...
   
   
  Failed Tests: There were 4 failures

    2) num_to_sxg

      ✗ 2^63
      ✗ 2^65

    3) sxg_to_num

      ✗ 2^63
      ✗ 2^65


  total:     16
  passing:   12
  failing:   4
  duration:  21ms

npm ERR! Test failed.  See above for more details.

% git rev-parse HEAD
0e8e6270c0a3b600423c283f59b5d22c3648d59a

This is freshly cloned, freshly npm install'd.

Ref #32