ultimately minimal unit testing

Most large software projects include automated testing and the reasons are obvious. But what about smaller, even toy projects? There should be some extremely lightweight unit-testing frameworks/libraries that would easily fit even the smallest project needs.

Unit testing should be easy to start. Otherwise people won’t bother with writing tests at all (unless they are forced to). People don’t like learning complex frameworks to run just a dozen of tests.

So here’s how my perfect unit testing library would look like:

Having these requirements in mind I made a couple of tiny testing libraries, I used them in some real-life projects and now I’m happy to share with you.

All of the libraries have common API of just 4 functions: test, ok, eq and spy. Try to guess what they do?

Lua: gambiarra

This is the one I used many times. Somehow Lua lacks good testing tools. Busted is bloated and hard to install if you can’t use luarocks. Lunatest and Luaunit are bloated and follow the JUnit style, which does not really help for small projects.

I made gambiarra. Here’s a minimal test module:

-- Gambiarra.lua is a single file that can be just copied into your source
-- tree and included. Once included it defines a test() function, that's the
-- only function is defines.
local test = require('gambiarra')

-- That's how you declare a new test. You pass a test name, a function and
-- optionally an async flag. If no async flag is passed, or if it's false
-- the test will finish right after the test function returns.
-- Otherwise you will have to call next() after the test is actually
-- finished.
test('My first test', function(next)
        -- Inside a test function you can use three more functions:
        --   ok, eq and spy

        -- ok(cond, [msg]) is the only assertion helper.
        ok(2 + 2 == 5, 'two plus two equals five')

        -- spy([f]) returns  function that records its every call (arguments,
        -- return values, errors) and optionally delegates the execution to
        -- the wrapped function
        local f = spy(mycallback)
        myfunc(f)

        -- arguments are stored in the f.called table. Table is nil if the spy
        -- was never called
        ok(f.called, 'callback was called')
        ok(#f.called == 2,' callback was called twice')

        -- eq(a, b) is a helper to deeply compare two variables. It works with most Lua data types.
        -- It's a handy way to compare tables.
        ok(eq(f.called[1], {'arg1', 'arg2'}), 'first call with two args: arg1 and arg2')

        -- Finally, you can use asynchronous code in your library, just call
        -- next() when you're done
        someasyncfunc(function()
            next() -- Go to the next test
    end)
end, true)

Simple? The whole library is about 120 lines of code, and gives you as much power as any other testing framework does. By default it prints some colorful test results to the console, but can be easily changed with a custom test handler:

test(function(event, testname, assertmsg)
    if event == 'pass' then ...       -- assertion passed
    elseif event == 'fail' then ...   -- assertion failed
    elseif event == 'except' then ... -- exception happened
    elseif event == 'start' then ...    -- new test started
    elseif event == 'end' then ...  -- test finished
    end
end)

And if you want to learn more - you can always read the code.

Javascript: klud.js

It was the first library of this family because I though that a testing library can be 1kB in size. Klud.js is similar to QUnit by its functionality but is much smaller.

It’s available on bitbucket, on microjs.com and via npm install kludjs and it has the same API as the Lua version has:

var test = require('kludjs');

test('setTimeout should work', function(next) {
    ok(typeof setTimeout === 'function', 'setTimeout is a function');
    var time = Date.now();
    setTimeout(function() {
        var delta = Date.now() - time;
        ok(delta >= 1000, 'setTimeout took ' + delta + ' ms');
        next();
    }, 1000);
}, true);

I used it for testing my Mithril code.

In fact the same test code works in the browser and in Node.js!

Unix shell: bricolage

Unix shell is an insteresting case. It’s kind of a programming language, but there is a big lack of modern tools for it. And even if you don’t want to use UNIX Shell - you still have to because it’s available in every linux system and it seems to be the only scripting language so widely available in the embedded linux world.

I used assert.sh and stub.sh in the past, they are really nice, but they are full of bashisms. So I decided to make my own testing library.

What are the specifics of the unix shell testing?

With this in mind I found that a text file seems to be the most portable data structure to use in UNIX Shell.

# A test is a function. $T is a variable where test keeps its internal files
mytest() {
    # ok is the only assertion helper
    # It uses `test` to check the condition, so syntax is common
    ok 1 -eq 1
    ok foo = foo
    foo="Foo bar"
    ok "$foo" = "Foo bar"

    # You can use `spy` to make a wrapper over a command.
    spy date

    date

    # Command output will be written into <spy>.stdout file:
    ok "$(cat $T/spy.date.stdout)" = "foo"

    # Fake spy output can be specified in the <spy> file:
    echo foo > $T/spy.date
    date

    # You can assert it using tail, sed, awk and other common unix tools
    ok "$(tail -n 1 $T/spy.date.stdout)" = "foo"
}

# You may override test reports as you need
pass() { echo PASS $* }
fail() { echo FAIL $* }

# You have to run your tests manually
bricolage mytest

# Clean test data
rm -rf $T

Here’s the library code

The resulting test library is extremely small (50 LOC), but I haven’t used it much yet so I can’t say if it’s stable enough.

What I like about it is that you can use it not only for shell code, but also for functional testing of some command-line apps.

What about C, Go, Java?

C does not have lambdas. So spies don’t make much sense in C if you have define spy functions during the compile phase - you can do it manually. Now, ok() can be replaced by a simple #define. eq() is either == or memcmp. And test() is just your function. So C is too low-level for this approach.

Go already has a perfect standard testing package. Yes, if/then are a bit annoying, and the lack of structure/method mocking, too. But in general it’s a very lightweight and easy to use library, and I really enjoy it.

Java… I don’t believe there would be an alternative to JUnit in this field, however a lot of things can be done in a simpler manner. For example I always struggle with asynchronous code testing. On the other hand, Mockito is a very sweet tool, so I don’t complain.

I wonder if there are other languages don’t have simple testing tools? What about Objective-C, Swift, Io, Tcl (no, I really don’t know)?

Anyway, summing up, testing can be fun, testing can be simple. And overcomplicated testing tools should not be an excuse to no unit testing.

Posted on 2014-12-16

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