Documentation: misleading deep inspection

[pytestbot]

Originally reported by: BitBucket: PeterSlickers, GitHub: PeterSlickers

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I recently started using pytest und thus read some the documentation.

On page "http://pytest.org/latest/assert.html" in section "Defining your own assertion comparison" I found an example 'test_foocompare.py'.

class Foo:
    def __init__(self, val):
         self.val = val

 f1 = Foo(1)
 f2 = Foo(2)
 assert f1 == f2

Class 'foo' is very simple and it does not define any of Pythons magic methods for comparison like ne, cmp etc. Thus, a comparison of two instances of Foo will be accomplished by comparing the unique ID of the two objects:

id(f1) == id(f2)

Even if both instances are initiated with the same value, the comparison for equality will fail:

id(Foo(1)) == id(Foo(1))  --> False

Applying the deep inspection produces the following misleading result:

'=================================================== FAILURES ===================================================
_________________________________________________ test_compare _________________________________________________

    def test_compare():
        f1 = Foo(1)
        f2 = Foo(1)
>       assert f1 == f2
E    assert Comparing Foo instances:
E         vals: 1 != 1

test_foocompare.py:9: AssertionError
1 failed in 0.01 seconds

With best regards

Peter

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• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/411

[pytestbot]

Original comment by holger krekel (BitBucket: hpk42, GitHub: hpk42):

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I agree that it's a bit confusing. Do you have an idea on how to improve it while keeping it simple enough? If so, are you maybe ready for a pull request?

thanks, holger