[import-bytes] add initial tests for import bytes proposal

[styfle]

• Closes Test plan for import bytes #4647

[ljharb]

there should be some kind of assertion that it's immutable (not sure what that'd look like tho)

same throughout

[styfle]

The lines below are checking for immutable (asserts that an error is thrown on resize and also on transfer)

assert.throws(TypeError, function() {
  value.buffer.resize(0);
});

assert.throws(TypeError, function() {
  value.buffer.transfer();
});

Let me know if there is a better way to check for immutability.

[anba]

Directly call the immutable accessor property https://tc39.es/proposal-immutable-arraybuffer/#sec-get-arraybuffer.prototype.immutable ?

[ptomato]

Note, the empty file is failing because fixture files need to contain the string _FIXTURE and these have a dash where they should have an underscore: https://github.com/tc39/test262/blob/main/INTERPRETING.md#modules

[styfle]

@ptomato Thanks! I updated the fixtures to use underscores and that solved the Test262File: missing "contents" error.

However, I ran into another error.

  File "/home/runner/work/test262/test262/tools/generation/lib/test.py", line 29, in load
    self.source = handle.read()
                  ~~~~~~~~~~~^^
  File "<frozen codecs>", line 325, in decode
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte

So I pushed some changes to the python code to ignore binary files.

I see there are still a few engines on circleci that are failing. Please let me know how to proceed, thanks!