Expect holds reference to value, generates error string at the end of test (after mutation)

[jimfb]

var foo = [1];
expect(foo).toEqual([1, 2]);
foo.length = 0;

expect should print the expected value as [1] but prints as [].

[zpao]

This might be a problem in Jasmine itself. Perhaps when/if we upgrade to a newer version of that this will just work.

[jimfb]

@cpojer, In #434 as a reason for closing the issue, you said:

Cloning here would be too expensive for performance. I understand this is an issue but the side-effect in your function is probably not something you'd want in your application anyway, I'll assume? While I do not know what your application is doing, shallow copying the object in your function Object.assign({}, obj) is probably reasonable.

I don't think you need to clone, just generate the string representation at expect time, for use in the error message when it gets printed. It shouldn't be that expensive (said without knowing the internals). Having code that mutates (especially adding to a list) is pretty damn common. And when you're debugging, this error is extraordinarily frustrating because you're banging your head against the wall going "how could that be?" only to realize that the test framework lied to you.

[cpojer]

Fixed in the next release.

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