Tests II

In most languages, a testing framework (ie ava in JavaScript, pytest in Python) is used to exeute a group of tests.

In Wall, tests that are co-located in files do not work this way. Instead, these tests execute at compile time.

expectEquals

Here is a simple test in Wall:

// simple-test.wall
@begin-test
expectEquals (+ 1 1) 2
@end-test

Let's look at the definition of the function expectEquals.

w> expectEquals = fun [_ _] ({ true } (== %k %%k))

As an exercise, try to spot how this function forces a compile error if %k %%k are not equal. Remember that { true } is the function { true: true } and that it invokes a bound version of (== %k %%k).