One way you can get what you want is to give up on the auto-gensym feature
of the #-terminated identifiers, and call gensym directly, enabling it to
be mocked out with with-redefs. E.g. instead of:

(defmacro m1
  [x f]
  `(let [x# ~x]
    (~f x#)))

do

(defmacro m1 [x f]
   (let [x-sym (gensym)]
     `(let [~x-sym ~x] (~f ~x-sym))))

You can then do something like

(defn new-gensym []
   (let [counter (atom 0)]
      (fn [& [extra]] (symbol (str (or extra "G_") (swap! counter inc))))))

(with-redefs [gensym (new-gensym)] (macroexpand-1 '(m1 1 inc)))

(not tested)

On Fri, Mar 27, 2015 at 5:50 PM, David James <davidcja...@gmail.com> wrote:

> I agree with this motivation behind this request, which I explain in more
> detail here:
> http://stackoverflow.com/questions/16745135/how-to-test-a-clojure-macro-that-uses-gensyms
>
> We should be able to test the behavior *and* the macroexpansion. (Most
> things in life are not simple either/or decisions. Don't believe people
> that tell you otherwise.)
>
> On Monday, March 23, 2015 at 12:58:49 PM UTC-4, Chris Ford wrote:
>>
>> I think it's useful to think of macros as an odd form of I/O. Just as you
>> would separate out your templating from your domain functions, separate out
>> your defmacro from regular functions that just happen to manipulate
>> symbols. These functions will be easier to test.
>>
>> On 23 March 2015 at 16:23, Sean Corfield <se...@corfield.org> wrote:
>>
>>> On Mar 22, 2015, at 7:52 PM, myguidingstar <phuthuycuo...@gmail.com>
>>> wrote:
>>> > I wonder if there is any way to make macro expansion in Clojure
>>> deterministic. That would be useful in unit tests.
>>>
>>> I'd be very interested to understand your use case... Testing what the
>>> macro expands to seems like it is test the macro system itself, not your
>>> own code. Surely in a unit test you'd want to test the _behavior_ of the
>>> code instead?
>>>
>>> Sean Corfield -- (904) 302-SEAN
>>> An Architect's View -- http://corfield.org/
>>>
>>> "Perfection is the enemy of the good."
>>> -- Gustave Flaubert, French realist novelist (1821-1880)
>>>
>>>
>>>
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-- 
Ben Wolfson
"Human kind has used its intelligence to vary the flavour of drinks, which
may be sweet, aromatic, fermented or spirit-based. ... Family and social
life also offer numerous other occasions to consume drinks for pleasure."
[Larousse, "Drink" entry]

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