Fri, 30 Nov 2007

Pumpkin Pie

This is from smakelijke gerechten, a cookbook assembled by the First Reformed Church in Oak Harbor, Washington in 1971. My grandmother's sister belonged to the church, and the cookbook was a gift for my grandmother's birthday.

Preheat oven to 425°F. Mix all ingredients. Pour into pie crust. Bake at 425°F for 15 minutes, then reduce temperature to 350°F and bake for 45 more minutes or until a toothpick inserted in center comes out clean.

Tue, 27 Nov 2007

Grandma's Potato Salad

While I was down in Texas for Thanksgiving, I got my grandmother to give me a couple of her recipes. Unfortunately, she was so familiar with the ingredients that she didn't have any measurements more specific than "'Til it tastes right," so that's all I can provide at the moment. I plan to make the recipe a few more times myself and figure out what measurements work well.

Scrub and boil the potatoes. Hard boil the eggs. When the potatoes are done, let them cool then peel them--the skins should rub right off. Cut the potatoes into roughly 1" pieces. Dice the eggs. Mix together potatoes, eggs, and onion.

In a separate bowl, mix the mayonnaise and pickle juice until the mixture is the right consistency. Add the curry powder, salt, pepper, and mustard to taste.

Mix the dressing with the potatoes, then sprinkle paprika over the salad.

Sun, 25 Nov 2007

Grandma's Parker House Rolls

While I was down in Texas for Thanksgiving, I got my grandmother to give me a couple of her recipes. She portions many of the ingredients by feel or taste, though, so this recipe assumes some familiarity with yeast breads. I plan to make them a couple of times and get some more exact measurements.

In a small saucepan, mix the milk with the sugar, salt, and 6 tablespoons of butter. Heat to just below a boil, then allow to cool to room temperature.

Proof the yeast in some water with a little sugar. Mix the yeast into the milk, then add enough flour to get the right consistency.

Knead the bread, then allow it to rise until doubled in size, about an hour.

Preheat the oven to 375°F.

Melt the remaining 2 tablespoons of butter. Flatten the dough, then roll it out to about 1/4" thick. Cut circles in the dough with a biscuit cutter or the opening of a glass. For each circle, dip half of one side in the butter, then fold it in half with the butter on the inside. Place the rolls on baking sheets and allow to raise until increased in size by roughly 50%.

Bake at 375°F until done, roughly 8-10 minutes.

Fri, 31 Aug 2007

Finding Duplicate Elements in an Array

I came across an interesting programming puzzle today, and I'd like to share a couple of variants on it.

To start with, let's say we have an array A that contains some numbers. For simplicity, let's say that the array is 1-based. How can we efficiently find out if any of those numbers are duplicates?

The easiest approach is to make a hash table to keep track of the numbers we've seen so far. Something like this:

Given an array A of length n,

let h ← (new hash table)
for 1 <= i <= n:
  if A[i] is present in h: return A[i]
  set h[A[i]] ← True
return <no duplicates>

Now, suppose that the array is of length n and only contains positive integers less than n. We can be sure (by the pigeonhole principle) that there is at least one duplicate. The bounds on the values mean that we can be a little more efficient and store the already-seen numbers in an array rather than a hash table:

let s ← array [1..n]
initialize s to all zeroes
for 1 <= i <= n:
  if s[A[i]] > 0: return A[i]
  set s[A[i] ← 1

Now, suppose that we have to do this in constant space; no more creating hash tables and arrays on the fly. Is if still possible? If you add the constraint that there be exactly one duplicate value, this is easy.

Since there are n values from 1 to n-1 with one duplicate, we can use the fact that the sum of the integers from 1 to m is (m*(m+1))/2, take the sum from 1 to n-1, subtract that from the actual sum of numbers in the array, and the result will be the duplicated number:

let s ← 0
for 1 <= i <= n:
  s ← s + A[i]
return s - n*(n-1)/2

But suppose there are no guarantees about the number of duplicates, and the only assurance you have is that the values are between 0 and n, exclusive. Is it still possible to find a duplicated value in O(n) time and O(1) space? Feel free to stop here and try to work things out yourself, if you want.

As you might have guessed from the length of this entry, there is an approach that will work. It's something of a radical departure from the previous approaches, and it relies rather heavily on the particular bounds we have on the values in the array.

First, there's the solution-by-cheating. If you're working in a language with bounded integers, you can exploit that knowledge to meet the letter of the law in the "constant space" requirement.

Let's say we're using a language and platform where integers are 32 bits, signed. The maximum value for an array element would therefore be 231-1, while the minimum value would still be 1. We only need one bit of information per value (seen/not seen), so, at 8 bits per byte, an array 223 bytes (8MB) long would be enough to track any set of integers the environment is capable of passing. This algorithm is therefore O(n) time and O(1) space on a system with 32-bit signed integers:

let s ← array [1..2^31-1] of bit
for 1 <= i <= n:
  if s[A[i]] = 1: return A[i]
  set s[A[i]] ← 1

Of course, it relies on implementation details that might change (a similar array on a 64-bit system would require 32 petabytes of memory) and it might be nice to have an algorithm that works regardless of any artifical bounds on your integers. Fortunately, there are a couple more approaches we can take.

Recall that the array is 1-based, so its elements are numbered from 1 to n. The values are positive integers less than n, so they can range anywhere from 1 to n-1. Because the values are a subset of the array bounds, we can treat those values as indices into the array itself.

If we're allowed to modify the array, we can just go through it reordering the elements, trying to put each value into the corresponding element (so the value 1 goes into the first element, 2 goes into the second element, and so on). When we find a collision, that's the duplicate.

for 1 <= i <= n:
  while A[i] ≠ i:
    if A[A[i]] = A[i]: return A[i]
    swap(A[A[i]], A[i])

If the array is immutable, though, the solution is a little more involved. Given the view of each value as an index into the array, we can treat the array as a directed graph, where each element is a node and the value of that element is an edge pointing at the next node. Since every node points to another node, there is at least one cycle in the graph. We can also conclude that every node leads to a cycle, even if it is not directly part of one.

(Side note on terminology, for those not immediately familiar: A graph is simply a collection of nodes and edges. Each edge connects exactly two nodes. In a directed graph, each edge also has a direction; it goes from one node to another. If you start at a particular node, follow (one of) its edges to the next node, continue doing that for a certain amount of time, and eventually come back to the starting node, that's a cycle. If you start at a particular node, follow its edges out in the same way, and end up in a cycle that does not contain the starting node, all of the nodes and edges you crossed before getting to the cycle are called the tail. The first node that you reach that is in the cycle is defined to be the beginning of the cycle. The symbols λ (lambda) and μ (mu) represent the lengths of the tail and cycle, respectively. Technically, the directed graph we're dealing with here is also a sequence, since every node has at most one edge leading away from it (though it might have more than one leading into it).)

Since the values in the array are all less than n, no element in the array can point to the nth element. Therefore, the last element cannot be part of a cycle. Since every element must lead to a cycle, it must be part of a tail. If we follow the sequence from this point, we will eventually run into a cycle, and the last element in the tail will be a duplicate value.

So, how do we find the beginning of the cycle? The easiest approach is to use Floyd's cycle-finding algorithm. It works roughly like this: Start at the beginning of the sequence. Keep track of two values (call them ai and aj). At each step of the algorithm, move ai one step along the sequence, but move aj two steps. Stop when ai = aj.

At this point, the difference between i and j must be a multiple of the cycle length. If the algorithm took m steps to get to this point, then i = m and j = 2m, so m is a multiple of the cycle length. i has also traveled λ steps along the tail and m-λ steps along the cycle.

If we now start another value (call it ak) at the beginning of the sequence and move both it and ai simultaneously and at the same rate, after λ steps, ak will have traveled the entire tail and will have arrived at the beginning of the cycle. At the same time, ai will have moved a total of m steps along the cycle and, since m is a multiple of μ, will also have arrived at the beginning of the cycle. Thus, if you stop as soon as ai = ak, you will have found the beginning of the cycle and the end of the tail.

So. Applying all of that to our problem means that we start at the last element of the array, have two variables following the pointers in the array, one going twice as fast as the other, until they are equal to each other. At that point, start one of them back at the beginning and run them at the same speed until they again equal each other. Their value will then be the duplicate value.

let i ← n, j ← n
do: i ← A[i], j ← A[A[j]]; until i = j
set j ← n
do: i ← A[i], j ← A[j]; until i = j
return i

This algorithm also lends itself nicely to functional programming, since it doesn't actually require any side effects, so here's an implementation in Haskell:

import Data.Array

findDup a = findDup' n $ findCycle (a!n) (a!(a!n))
    where n = snd $ bounds a
          findCycle i j | i == j    = i
                        | otherwise = findCycle (a!i) (a!(a!j))
          findDup' i j | i == j    = i
                       | otherwise = findDup' (a!i) (a!j)

Sun, 01 Jul 2007

Reply-To: for Mailing Lists

Many mailing lists I'm on (particularly ones inhabited by sizable portions of geeks) have periodic "discussions" about the behavior of the Reply-To header on list email. The discussions usually follow fairly predictable paths. "Reply-To" Munging Considered Harmful is quoted. Proponents respond with Reply-To Munging Considered Useful.

My opinion is threefold:

First, not touching the header is the purest solution. For all the reasons in "Reply-To Munging Considered Harmful", mailing lists shouldn't touch it, in an ideal world, at least.

Second, "Reply-To Munging Considered Useful" gets one things right: it adds functionality. Even today, most mail clients can either "reply" or "reply-to-all". If "reply" goes to the message originator, then they're left with "reply-to-all" as the easiest way to send a message to the list. (And sending mail to the list should, in most cases, be easy.) Some MUAs, such at mutt and KMail [please email me if you know of others] add a "list-reply" function. If most common MUAs had such a feature, I would find it much easier to advocate against munging. But they don't, and it's rather elitist to insist that people switch MUAs just for your mailing list. So, in today's world and for an average list, I tend to vote for munging the header. (Though I really like the (void) mailing list, which provides twin lists, one with munging, the other without. All posts do, of course, appear on both lists.)

(Note that "reply-to-all" is not the same as "list-reply". "list-reply" sends one message--it goes to the list (unless the original email has a Mail-Followup-To: header, but that's another post). "reply-to-all" sends one message to the list, plus one message for each sender and recipient of the original email. That adds up quickly for involved discussion threads, and all of those extra messages are wasts of both time (human and computer) and bandwidth.)

Third, I don't have to care either way, because I use mutt and procmail. (And, actually, the procmail part is optional.) In my .procmailrc is the following recipe:

:0 fhw
| sed -e "s/^\\(Subject:.*\\)\\[$MATCH\\]\\( \\)*/\\1/I" \
      -e "/^Reply-To:.*$MATCH@/ d" \
      -e "s/^Old-Reply-To:/Reply-To:/"

$MATCH is already set to the name of the mailing list, which is usually also the local portion of its email address. (Note that this loses information if the list doesn't munge the header and someone has their own Reply-To header that happens to have the same local part as the mailing list. In my experience, this is highly unlikely.)

My mutt config contains the following directives:

set ignore_list_reply_to=yes
set reply_to=yes
subscribe <list addresses>

so if a Reply-To header is set to an email address that mutt knows to be a mailing list, it ignores that header. (And since those are ignored, I set "reply_to" to yes, so it always uses acceptable headers; by default it asks whether I want to use them.) Thus, the "r" key always replies to the person who sent the message, the "g" key always replies to the sender and all recipients of the message, and the "L" key sends the reply to the mailing list the email was from (and any other addresses in the Mail-Followup-To header).

Thu, 08 Mar 2007

Common Lisp Testing Frameworks

I've been evaluating the various Common Lisp testing frameworks. I have a large body of code in my Project Euler stuff, and I use unit testing extensively; extensively enough that the simplistic unit testing package I had been using was getting unwieldy. So I figured I'd take a look at what was available and see how everything stacked up.

Since this page is long, I'll present my summary up front: If your testing needs are simple, use lisp-unit. It you need many, well-organized tests (as I now do), use either Stefil or FiveAM, depending on whether you want highly-interactive or noninteractive tests, respectively.

First, a bit about my requirements. I use packages extensively in my Project Euler setup. I have a main package, :euler, which contains "common" code, both things that are used extensively, like my primality testing function, and things that might only be used in one place, but that seemed like they belonged in the common section, like the implementation of Dijkstra's shortest-path algorithm or the function for finding a minimum spanning tree. I have unit tests for most of these functions. (Not all yet, but I'm working on it.) There is a separate package for each problem, into which goes at least a function named get-answer as well as any other problem-specific code and tests. The problem-specific tests include at least tests to check my code against the examples given in the problems and (when I've gotten it) a test for the answer to the problem. I generally want to do one of three things: test everything, test just one problem's code, or test the library functions. I occasionally want to test just the answers to all of the problems, too.

In setting up the tests, I wrote a few macros and put all of my tests in those so I could redefine the test framework easily. When I could use hierarchies, I set them up as follows: suite euler-tests is the root of the tree. It contains euler-functions and euler-problems. euler-functions contains a suite/test (depending on the particular framework) for each common function. euler-problems contains one suite for each problem, of the form euler-<problem-number>-tests. That suite contains a test/suite for the examples given in the problem (euler-<problem-number>-givens), one for the answer (euler-<problem-number>-answer), and possibly one for each internal function I want to test (euler-<problem-number>-<function-name>). In my example runs, I've deliberately introduced several errors: a function signalling an error when it shouldn't and vice versa, a function returning t when it should return nil and vice versa, and a couple of functions that return an incorrect (numerical) value.


lisp-unit was the package I'd been using, and I like it because it's dead simple to work with. It uses packages to group the tests, so your existing package structure serves the part of test suites. Obviously, they're not even hierarchical, let alone composable. There are no fixtures. While the design lacks some flexibility, since it's tied directly to the package system, it makes up for it in simplicity. Because there's no need to declare and organize your test suites, adding a test is as simple as

(lisp-unit:define-test <test-name>

The test clauses use the fairly obvious assert-true, assert-false, assert-equal, and assert-error tests (plus a couple of others). Running the tests is either a matter of (run-tests <test-names>), which runs tests in the current package (if no names are given, all tests are run); or (run-all-tests <package> <test-names>) to use a different package (again, listing no tests will run them all).

The main drawbacks for large bodies of tests are that there's no composition of test suites, so you have to give explicit commands to run all of your tests, and it prints one line for each test. Here's a sample run:

* (eval
      (lisp-unit:run-all-tests euler)
      ,@(loop for i from 1 to 142
              collect `(lisp-unit:run-all-tests
                        ,(intern (format nil "E~3,'0D" i)))))))
EULER-BOUNCYP: 17 assertions passed, 0 failed.
EULER-LEAST-DIVISIBLE-REPUNIT: 2 assertions passed, 0 failed.
EULER-MODPOWER: 6 assertions passed, 0 failed.
EULER-NEXT-PRIME: 9 assertions passed, 0 failed.
EULER-NUM-PARTITIONS: 12 assertions passed, 0 failed.
Expected T but saw NIL
EULER-PALINDROMEP: 35 assertions passed, 1 failed.
EULER-PREV-PRIME: 7 assertions passed, 0 failed.
Should have signalled ERROR but saw T
EULER-PRIMEP: 11 assertions passed, 1 failed.
Expected NIL but saw T
EULER-UNIQUE-DIGITS-P: 9 assertions passed, 1 failed.
TOTAL: 108 assertions passed, 3 failed, 0 execution errors.
EULER-001-ANSWER: 1 assertions passed, 0 failed.
EULER-001-GIVENS: (GET-ANSWER 10) failed: 
Expected 24 but saw 23
EULER-001-GIVENS: 0 assertions passed, 1 failed.
TOTAL: 1 assertions passed, 1 failed, 0 execution errors.
EULER-002-ANSWER: 1 assertions passed, 0 failed.
EULER-002-GIVENS: 1 assertions passed, 0 failed.
TOTAL: 2 assertions passed, 0 failed, 0 execution errors.

[ 72 lines snipped ]

EULER-035-GIVENS: 1 assertions passed, 0 failed.
EULER-035-ROTATE-NUM: (ROTATE-NUM 1 1) failed: 
Expected 2 but saw 1
EULER-035-ROTATE-NUM: 9 assertions passed, 1 failed.
TOTAL: 11 assertions passed, 1 failed, 0 execution errors.

[ 123 lines snipped ]

    EULER-095-ANSWER: The value -1 is not of type (MOD 536870911).

[ 87 lines snipped ]

In most cases, the error test is very informative. It gives the code that it ran, the expected return value, and the actual value. The only exception is when an unexpected error was signalled; in that case, only the test name is given. The problem, as you can see, is that these informative failure messages get lost among all the noise of the successful tests. The fact that there's no composition means that you don't even get a count of total failed tests at the end. (That is a failing of many of the Common Lisp test frameworks available).

lisp-unit's main strength is that it's easy to use. For simple testing situations, it's easily the best one available, because it's so easy to use there's no barrier to writing all the tests you need. Its failure messages are useful and informative. Its main drawback is that it doesn't scale well. If your test needs are simple then lisp-unit is probably the best choice for you.


Initially, LIFT looked good. It's obviously influenced by JUnit's ways of doing things. Test suites are defined very much like CLOS classes; they have a hierarchical inheritance structure (with multiple inheritance, even) and can have slots just like CLOS classes. Fixtures for setting up and tearing down resources for the tests are supported (with the resources references by custom slots). The test running function simply returns a test result object, but the package uses the pretty-printing function for that object to detail the test results, which is rather neat and would lend itself well to automated processing of the test results. Another interesting feature is randomized testing based on a specification, similar to QuickCheck for Haskell.

Setting up tests requires defining a test suite and adding tests to it, which can either be done in one statement:

(lift:deftestsuite <suite-name> (<parent-suites>)
    <forms to set up the slots>)
    <forms to tear down slots>)

or, since everything after the slot definitions is optional, in multiple statements:

(lift:deftestsuite <suite-name> (<parent-suites>)
(lift:addtest (<suite-name>)

(Note that having the suite name in a list for addtest is a special case. Normally, that parameter would be a symbol giving the name of the test, which would be placed in the most recently-defined test suite. Using a list with a suite name in it overrides that behavior and assigns the test to a specific suite and gives the test a name of the form test-<number>. Another special case is that you can omit both the name and the suite; when the first form is a list of more than one element, it is treated as a test clause and the test is given an autogenerated name (as above) and placed in the most recently-defined test suite.)

Test clauses are very much like lisp-unit's, except that the test macros have slightly different names: ensure (analogous to lisp-unit:assert-true), ensure-same, and ensure-error. The analog to (lisp-unit:assert-false <form>) is (ensure (not <form>)).

The fact that test suites support multiple inheritance is a nice touch. In my setup, it means that I could have an additional suite named euler-answers, and every answer suite would inherit from both its project's test suite and the euler-answers suite. That way I would have a suite that would run just the tests on the problems' answers without interfering with the rest of my test hierarchy structure. Of the test frameworks I looked at, LIFT was the only one with multiple inheritance for test suites.

One feature that's not in LIFT just yet but which the author has mentioned adding is support for benchmarking tests. This is something that would really interest me, especially in conjunction with being able to run just the tests on the problem answers. (I've actually got some code that did benchmarking of my lisp-unit code, and I've used it to target my optimization of problems. Having support for that sort of thing baked into the testing framework would be very nice.)

Test and suite names appear to be effectively global; as far as I can tell, they're compared by string= on symbol-name. This means that it's easy to call tests that were defined in a different package than the current one, but it also means that the normal package exporting rules don't apply, and all names must be globally unique.

That's all good stuff. There were a few problems I ran into. First, whenever I defined a test, SBCL raised a style-warning about redefining things in defmethod, even if it was the first time I'd defined the test. SLIME didn't quite understand the warnings, so everytime I compiled a test suite or file, I got an extra SLIME window listing all the spurious warnings.

The larger problem, though, was its speed and memory footprint. Defining tests is very slow; when using LIFT, the time necessary to compile and load all of my Project Euler code jumped from the other frameworks' average of about 1.5 minutes to over nine minutes. Redefining tests felt even slower than defining them initially, but I don't have solid numbers on that. After loading everything, memory usage was more than twice that of other frameworks. Running all of the tests took more than a minute longer than other frameworks, though that seems mostly to be a result of swapping induced by LIFT's greater memory requirements.

Here's a sample run:

* (lift:run-tests :suite 'euler-tests)
#<Results for EULER-TESTS 380 Tests, 5 Failures, 1 Error.

Failure: euler-primep : test-12
  Condition: Expected ERROR but got NIL

Failure: euler-palindromep : test-36
  Condition: Ensure failed: (EULER:PALINDROMEP 10221) ()

Failure: euler-unique-digits-p : test-10
  Condition: Ensure failed: (NOT (EULER:UNIQUE-DIGITS-P 1)) ()

Failure: euler-001-givens : test-1
  Condition: Ensure-same: 24 is not EQUAL to 23

Failure: euler-035-rotate-num : test-1
  Condition: Ensure-same: 2 is not EQUAL to 1

ERROR  : euler-095-answer : test-1
  Condition: The value -1 is not of type (MOD 536870911).

As I mentioned before, the use of the print-object generic function to give a summary of the tests is very nice. The fact that it only details failures is also quite nice; failures aren't lost in the noise of successful tests. The reporting of the failures isn't quite as nice as in lisp-unit. While failures of ensure show the code that failed, failures of ensure-same merely show the mismatched values, not the code that generated the values.

There's no feedback while the test routines are running, which is a minor annoyance, but completely in keeping with the nature of functional programming.

Overall, LIFT is an intriguing framework with a lot of good things going for it, but the speed and memory issues killed it for me. It might work better with fewer test cases and suites, but in that case I'd probably recommend just using lisp-unit and its elegant simplicity.


XLUnit bills itself as a low-programmer-overhead adaptation of JUnit. It's based on both XPTEST and clos-unit (so I didn't bother trying either of those individually). It follows the approach of JUnit in using native OO classes as test suites; each suite is simply a CLOS class that inherits from the test-case class. It does have its own macro for declaring test cases, but its format reads very much like a generic method being specialized on a particular class. Likewise, fixtures are supported by implementing the set-up and tear-down generic functions for your test suite class. The main drawback is that, although you can create hierarchies of test suites (since they're just CLOS classes), the suites aren't composable.

Setting up tests is pretty simple:

(defclass <suite-name> (xlunit:test-case)
(xlunit:def-test-method <test-name> ((test <suite-name>))

XLUnit uses fairly standard names for its test clauses, too: assert-true, assert-false, assert-equal, assert-condition, assert-eql, and assert-not-eql.

The UI is pretty similar to the standard *Unit text interface, too:

* (xlunit:textui-test-run (xlunit:get-suite euler-tests))
Time: 0.072

There were 3 failure:
3) EULER-PRIMEP: Assert condition ERROR, but no condition signaled

Run: 9   Failures: 3   Errors: 0

* (xlunit:textui-test-run (xlunit:get-suite e001::euler-001-tests))
Time: 0.002

There was 1 failure:
1) EULER-001-GIVENS: Assert equal: 24 23

Run: 2   Failures: 1   Errors: 0

* (xlunit:textui-test-run (xlunit:get-suite e095::euler-095-tests))
Time: 0.138

There was 1 error:
1) EULER-095-ANSWER: The value -1 is not of type (MOD 536870911).

Run: 1   Failures: 0   Errors: 1

It prints dots, 'F's, and 'E's as it runs each test and then summarizes the failures. As with LIFT, it gives details of the code that failed in some cases (assert-true, assert-false), but not in others (assert-equal, assert-error, unexpected condition).

The def-test-method macro feels a little clunky to me. I'd rather see the class instance and test suite named separately from each other, but I think part of that is just experience with other test frameworks that worked differently. It does make plenty of sense when viewed as just an extension of CLOS. The non-composability of suites is what really kills XLUnit for me. If I didn't want composition, I'd still be using lisp-unit, which has even less syntactic overhead and comparable resource usage. I'd say it has some usefulness for situations where you needed fixtures but still wanted a simple programming interface to the framework.


Initially, FiveAM reminded me a bit of LIFT with fewer gee-whiz features. It, too, does hierarchical, composable test suites. (In fact, it was the only other framework that supported composing suites.) It also does fixtures, but somewhat differently than anyone else. In FiveAM, fixtures are written as macros with a special keyword indicating where the test body will go. On one hand, it's a very Lispy approach to the issue. (In particular, it lets you keep all of your state in local variables, which is a bit more functional style than the OO approach of using class slots.) On the other hand, you have to wrap every set of tests that use the fixture in a with-fixture macro, while most other approaches tie the fixtures to the test suite so they're set up and torn down automatically for each test in the suite.

Like LIFT, FIveAM has support for specification-based random testing. I don't have anywhere I use things like that, so I again didn't test it.

FiveAM also has fewer test clauses; most cases will work with the is macro, which codewalks its body to determine what exactly is being tested.

Test suites are pretty easy to create:

(5am:def-suite <suite-name>)

It supports inheritance (and documentation) with key parameters:

(5am:def-suite <suite-name> :in <parent-suite>
               :documentation <doc-string>)

Test may either be bound to suites explicitly:

(5am:test (<test-name> <dependencies> <suite>)

or implicitly, as with the in-package form:

(5am:in-suite <suite-name>)
(5am:test <test-name>

The <dependencies> parameter is for declaring that a given test depends on another test completing successfully (or failing) first.

Sample run:

* (time (5am:run! '5am-euler-tests))
 Did 381 checks.
    Pass: 375 (98%)
    Skip: 0 ( 0%)
    Fail: 6 ( 1%)

 Failure Details:
      Failed to signal a ERROR.
      10221 did not satisfy PALINDROMEP.
      1 satisfied UNIQUE-DIGITS-P.
 EULER-001-GIVENS []: 
      23 was not = to 24.
      1 was not = to 2.
 EULER-095-ANSWER []: 
      Unexpected Error: #<TYPE-ERROR {B2B7639}>
The value -1 is not of type (MOD 536870911)...

As with other *Unit frameworks, it prints one character for each test run, giving a bit of visual feedback. The failure messages are decent, but (as with most frameworks) no code is shown for unequal values.

Overall, I like FiveAM slightly more than the other frameworks I tried. (Though I like lisp-unit's failure messages, XLUnit's approach to fixtures, and several of LIFT's current and proposed features more than FiveAM.) FiveAM does support the one killer feature I was looking for--hierarchical, composable test suites--as well as a number of smaller things that seem very nice and in the spirit of Lisp.


ptester is barely a test framework. It has no test suites and no test functions. All it provides is a set of macros for checking function results (test (analogous to lisp-unit:assert-equal), test-error, test-no-error, test-warning, and test-no-warning) and a wrapper macro designed to enclose the test clauses which merely provides a count of success and failures at the end. ptester expects that all testing is done in predefined functions and lacks the dynamic approach present in other frameworks.

I didn't bother trying ptester with my code. The lack of any sort of organization meant that I would have had to rewrite most of my tests to get them all called properly. (I would have to put each set of test clauses in a function and then have the function called from somewhere. Compare to most frameworks, where the test is told which suite or clause it belongs to and running the suite automatically gets all of the tests it contains.)


Although there's a Debian package for CLUnit, it didn't load properly into my environment (SBCL; it complained that the function deftest was undefined. A survey of the documentation indicates that it's lacking my single most important requirement: a composable test suite hierarchy. I thus didn't spend much time trying to get it to work.

It does support grouping of tests, but not hierarchically. There are no fixtures. Tests are named with strings, which bypasses some of the scope problems that can arise when using symbols. The use of function passing looks a little clunky to me, but it could be abstracted away with a macro if necessary. It does support multiple value returns, which sets it apart from most other frameworks I looked at (MSL.TEST does them, as does ptester, though ptester only considers the first return value by default).

A simple test definition looks roughly like this:

(clunit:deftest "<test-name>"
  :category "<suite-name>"
  :test-fn (lambda () <test-clauses>))

The test is considered to have failed if test-fn returns nil; otherwise, it succeeded.

The functionality of other frameworks' test clause macros (lisp-unit:assert-same, etc.) is accomplished by use of other keyword arguments passed in to the deftest clause. For example, this lisp-unit test

(lisp-unit:define-test addition
  (lisp-unit:assert-equal 2 (+ 1 1)))

could be rendered as

(clunit:deftest "addition"
    :input-form '(1 1)
    :test-fn (lambda (args)
               (destructuring-bind (a b) args
                 (+ a b)))
    :output-form 2)

which, yes, is wordier, but the various keywords allow for some interesting combinations of tests.

When the tests are run, the names of failed tests are given, but nothing more. The setup appears to highly encourage one clause per test, so that imprecision shouldn't be too much of an impediment.

I didn't really experiment with this one much, since it failed to compile and was missing a key feature, but it does seem to have an interesting approach to testing. I fear, though, that its approach adds too much complexity to the process.


FReT also did not compile for me. It ran into problems with some of its internal macros. It says it is based on LIFT, which I'd already dismissed, and it has no documentation available aside from the source. I opted not the spend the time investigating it further.


MSL.TEST is another basic test framework. It checks multiple value returns by default, which is nice (though it made a bunch of my previously-passing tests fail; all the other frameworks I tried only compared the primary return value by default). The framework only has test groups, not a hierarchy, but it uses the return value of its test clauses to determine success or failure, and the run-tests function returns t only if all of its tests succeeded, so you can fake a hierarchy be having one of your test clauses run the tests in a different group. The test results are not aggregated, though, and its output format is very noisy, printing one line per passing test and more for failing tests.

Excerpt of a sample run:

* (time (msl.test:run-tests 'euler-tests))
** PASS: EULER-MODPOWER            [00:00:00.00]
** FAIL: EULER-PRIMEP              [00:00:00.00]
** PASS: EULER-PREV-PRIME          [00:00:00.00]
** PASS: EULER-NEXT-PRIME          [00:00:00.00]
Form: (PALINDROMEP 10221)
Expected value: T
Actual value: NIL.
** FAIL: EULER-PALINDROMEP         [00:00:00.00]
** PASS: EULER-NUM-PARTITIONS      [00:00:00.05]
Expected value: NIL
Actual value: T.
** FAIL: EULER-UNIQUE-DIGITS-P     [00:00:0.004]
** PASS: EULER-BOUNCYP             [00:00:00.00]

Ran 9 of 9 tests in group EULER-FUNCTIONS
The following tests failed:

Totals -- Passed: 6       67%
          Failed: 3       33%
** PASS: EULER-001-ANSWER          [00:00:00.00]
Test EULER-001-GIVENS failed
Form: (EULER-001:GET-ANSWER 10)
Expected value: 24
Actual value: 23.
** FAIL: EULER-001-GIVENS          [00:00:00.00]

Ran 2 of 2 tests in group EULER-001::EULER-001-TESTS
The following tests failed:

Totals -- Passed: 1       50%
          Failed: 1       50%
** FAIL: EULER-001-SUBGROUP        [00:00:00.00]
** PASS: EULER-002-ANSWER          [00:00:00.00]
** PASS: EULER-002-GIVENS          [00:00:00.00]

Ran 2 of 2 tests in group EULER-002::EULER-002-TESTS

Totals -- Passed: 2      100%
          Failed: 0        0%
** PASS: EULER-002-SUBGROUP        [00:00:00.00]

[ 78 lines snipped ]

Test EULER-013-ANSWER failed
Expected value: 5537376230
Actual values: 5537376230
** FAIL: EULER-013-ANSWER          [00:00:0.004]

Ran 1 of 1 test in group EULER-013::EULER-013-TESTS
The following tests failed:

Totals -- Passed: 0        0%
          Failed: 1      100%
** FAIL: EULER-013-SUBGROUP        [00:00:00.01]

[ 651 lines snipped ]

Test EULER-095-ANSWER failed
The value -1 is not of type (MOD 536870911).
** FAIL: EULER-095-ANSWER          [00:00:00.22]

Ran 1 of 1 test in group EULER-095::EULER-095-TESTS
The following tests failed:

Totals -- Passed: 0        0%
          Failed: 1      100%
** FAIL: EULER-095-SUBGROUP        [00:00:00.22]

[ 333 lines snipped ]

Ran 140 of 140 tests in group EULER-PROBLEMS
The following tests failed:

Totals -- Passed: 124     89%
          Failed: 16      11%
** FAIL: EULER-TEST-CHILDREN       [00:03:26.29]

Ran 1 of 1 test in group EULER-TESTS
The following tests failed:

Totals -- Passed: 0        0%
          Failed: 1      100%

MSL.TEST is exceedingly wordy, too much so for feasably running any large number of tests. As usual, I feel that in situations where the requirements are simple enough that MSL.TEST would work well, lisp-unit would work equally well, if not better.


Stefil takes a much more interactive approach to testing. It is intended primarily for use from the REPL, preferably running within SLIME. Test failures are reported by raising conditions with information about the failing test:

Test assertion failed:

Binary predicate (= X Y) failed.
x: 24 => 24
y: (EULER-001:GET-ANSWER 10) => 23
   [Condition of type STEFIL::ASSERTION-FAILED]

  0: [CONTINUE] Record the failure and continue
  1: [CONTINUE-WITHOUT-DEBUGGING] Record the failure, turn off debugging for this test session and continue
  2: [CONTINUE] Skip the rest of the test (STEFIL::NAME-OF STEFIL::TEST) and continue
  3: [RETEST] Rerun the test (STEFIL::NAME-OF STEFIL::TEST)
  4: [CONTINUE] Skip the rest of the test (STEFIL::NAME-OF STEFIL::TEST) and continue
  5: [RETEST] Rerun the test (STEFIL::NAME-OF STEFIL::TEST)
  6: [CONTINUE-WITHOUT-DEBUGGING] Turn off debugging for this test session and invoke the first CONTINUE restart
  7: [ABORT-TESTING] Abort the entire test session started with EULER-001::TEST-ALL
  8: [ABORT-REQUEST] Abort handling SLIME request.
  9: [TERMINATE-THREAD] Terminate this thread (#<THREAD "repl-thread" {AF0CB91}>)

                               x: ~S => ~S~%~
                               y: ~S => ~S" :FORMAT-ARGUMENTS ((= STEFIL::X STEFIL::Y) 24 24 #1# 23)))
 -- more --

Defining a test (via deftest) results in a function with the same name as the test; running that function runs the test. Tests are completely composable; you can call one test from within another and their results are aggregated. Test suites are defined by defsuite, but internally suites are just tests that call other tests. Adding a new test to a suite just adds that test's function to the functions called by the suite's function. Likewise, creating a suite adds it to the current suite, giving you a hierarchy. My only problem with the setup is that I don't see a way to explicitly assign tests to suites, aside from dynamically binding stefil::*suite*. Normally, the current suite is set by in-suite, which requires careful attention if you're jumping between different suites often. (A somewhat mitigating factor is that tests remember which suite they were created in, so the current suite only matters for newly-defined tests.)

As an example of a hierarchy, here's roughly how I set up things for my tests:

(in-package :euler)

(stefil:defsuite* test-all)
(stefil:defsuite test-functions)
(stefil:defsuite test-problems)

(stefil:in-suite test-functions)

(stefil:deftest test-modpower ()
  (stefil:is (= 399 (modpower 123456 123456 789))))

(in-package :e001)

(stefil:in-suite euler:test-problems)
(stefil:defsuite* test-all)

(stefil:deftest test-answer ()
  (stefil:is (= <answer> (get-answer))))
(stefil:deftest test-givens ()
  (stefil:is (= 24 (get-answer 10))))

Note that (defsuite* <suite-name>) is equivalent to (defsuite <suite-name>) followed by (in-suite <suite-name>).

Fixtures are supported in pretty much the same way that FivaAM does them; you define them as macros and then run your tests within a with-fixture macro.

Running the tests looks like this:

* (test-all)
#<test-run 362 tests, 381 assertions, 6 failures in 169.139 sec>

That is, of course, only half the picture, since failures are reported by raised conditions, and that returned object is designed to be browsed with the SLIME inspector. I showed the full debugger response to a condition earlier; here are the other messages from test failures I saw in my run:

Test assertion failed:

(PROGN (PRIMEP 2)) failed to signal condition ERROR
   [Condition of type STEFIL::ASSERTION-FAILED]


Expression (PALINDROMEP 10221) evaluated to false
0: 10221 => 10221
   [Condition of type STEFIL::ASSERTION-FAILED]


Expression (NOT (UNIQUE-DIGITS-P 1)) evaluated to true
0: 1 => 1
   [Condition of type STEFIL::ASSERTION-FAILED]


Binary predicate (= X Y) failed.
x: 24 => 24
y: (EULER-001:GET-ANSWER 10) => 23
   [Condition of type STEFIL::ASSERTION-FAILED]


The value -1 is not of type (MOD 536870911).
   [Condition of type TYPE-ERROR]

I like that you get lots of information about the code that was run, the result it produced, and the result that was expected. The only thing that could be clearer is the actual test that failed. You either have pore through the backtrace or wait for everything to finish and pore through the test result objects.

Speaking of test result objects, here's the one returned by the test. It's got a lot of information in it.

An object.

failure-descriptions is an array containing an object for each failed test. run-tests is a hash table with one entry for each test run; the keys are the test objects and the values are "test context" objects.

Here's what one of the "assertion failed" objects looks like

An object.
TEST-CONTEXT-BACKTRACE = (#<test-run (EULER-001::TEST-GIVENS)> #<test-run (EULER-001:TEST-ALL)> #<test-run (TEST-PROBLEMS)> #<test-run (TEST-ALL)>)
FORMAT-CONTROL = "Binary predicate ~A failed.~%~
                               x: ~S => ~S~%~
                               y: ~S => ~S"

And here's what a test context object looks like.

An object.
PARENT-CONTEXT = #7=#<test-run (EULER-001:TEST-ALL)>

I like the touch of having the test's runtime available. As I mentioned in the LIFT section, I'd written some functions to gather that data myself, but having the test collect it for me is even nicer.

I'm fairly impressed with Stefil. It's got a very interesting interface, and the use of the debugger and inspector lends itself well to the interactive, short feedback cycle of Lisp programming. I'm not sure if the approach will work for everyone, but I'm going to give Stefil an extended try and see how well its testing approach works for me. If the live testing proves too bothersome, I'll just use FiveAM.

Mon, 12 Feb 2007

E Pluribus Unicorn

E Pluribus Unicorn is a collection of short stories by Theodore Sturgeon. All of the stories were written between 1947 and 1953, though they don't seem very dated, aside from occasional archaic-sounding language usage.

The stories are mostly fantasy, though some could be considered almost horror; many are certainly unsettling, most notably The Professor's Teddy-Bear, with Bianca's Hands (and perhaps A Way of Thinking) a close second. Die, Maestro, Die! reminded me of Edgar Allan Poe, in structure, if not in style. There's an element of melancholy in several of the stories, including The SIlken-Swift, Scars (which has no elements on fantasy, but is simply a good story), and especially A Saucer of Loneliness.

Overall, I enjoyed the collection; I hadn't read much by Sturgeon before, and I quite like his writing.

Phil! Gold