Question

我试图在Ruby中单元测试一个类的两个实例的相同性：

def test_example
    a = Object.new
    b = Object.new

    assert_equal a, b
end

我理解这是失败的，因为实例是不同的变量，每个变量都有自己的内存指针。我所追求的是如果实例在所有方面都相同但是它们的参考指针都要通过这个测试。

这是一个更具参与性（如果做作）的例子：

# Let's stir up something...
class FooBar
    attr_accessor :seed, :foo, :bar

    def foo_the_bar()
        @bar = @seed + @foo * 3
    end
end

f = FooBar.new
f.seed = "Mountains "
f.foo  = "are just mountains "
f.bar = "obliterate me!"
f.foo_the_bar
p f.bar # "Mountains are just mountains are just mountains are just mountains "


# So far so good, now let's test if one FooBar is same as another...

require 'test/unit'
class FooBarTest < Test::Unit::TestCase

    # Test fails: <#<FooBar:0x9a40d18>> expected but was <#<FooBar:0x9a40d04>>.
    # But what we really want is a way to make this pass
    # since the objects are exactly the same in every respect,
    # besides their pointers.
    def test_foobar_1_init
        f1 = FooBar.new
        f2 = FooBar.new

        assert_equal f1, f2
    end

    # Again, test fails, but we want it to pass,
    # since the instance variables are the same.
    def test_foobar_2_instance_var
        f1 = FooBar.new
        f2 = FooBar.new

        f1.seed = "Santa says "
        f1.foo = "ho "
        f1.bar = "something"
        f1.foo_the_bar

        f2.seed = f1.seed
        f2.foo = f1.foo
        f2.foo_the_bar

        assert_equal f1, f2
    end

    # This test fails for the wrong reason.
    # We want this to fail because the instance variables are different.
    # This test should also fail if we add a method to one of the instances,
    # or make the instances differ from each some other way.
    def test_foobar_3_diff
        f1 = FooBar.new
        f2 = FooBar.new

        f1.seed = "Kitty goes "
        f1.foo = "meow "
        f1.foo_the_bar

        f2.seed = "Doggies goes "
        f2.foo = "woof "
        f2.foo_the_bar

        assert_equal f1, f2
    end
end

Answer 1

f1.attributes.keys.collect(&:to_sym).each do |field|
 assert_equal f1.send(field), f2.send(field)
end

这将断言所有字段的相等性。但缺点是断言的数量。如果您不希望这种情况发生，请将id分配给像这样的对象

f1.id = 1
f2.id = 1 
assert_equal f1, f2

但请务必不要保存可能导致不一致的对象。

Answer 2

只需定义FooBar#==方法：

class FooBar
  def ==(other)
    [bar, seed, foo] == [other.bar, other.seed, other.foo]
  end
end

现在test_foobar_1_init和test_foobar_2_instance_var通过，test_foobar_3_diff因正当理由而失败。

缺点是当您更改对象结构时，需要相应地修改==方法。

Answer 3

根据apidock的源代码，assert_equals首先使用inspect方法将对象转换为字符串。您应该为class FooBar

定义检查方法

class FooBar
  def inspect
    # create a unique string of attributes here, maybe a json string.
  end
end

如何在Ruby中对类实例的相同性/相等性进行单元测试？

3 个答案: