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MoonScript spec guide

Testing the right code

Because MoonScript is written in MoonScript, and MoonScript specs are written in MoonScript, you need to be aware of which copy of MoonScript is actually executing the specs.

A system installed version of MoonScript is recommended to run the specs (and for development). This means that you'll typically have two versions of MoonScript available in the load path:

  • The system version
  • The version in the current directory

A system install is recommended because you'll always want a functioning version of MoonScript to compile with in case you break your development version.

When developing you want to make ensure the tests are executing your changes in the current directory, and not testing the system install.

Busted itself is MoonScript aware, so it means it should have a functional MoonScript compiler in order to load the .moon test files. This should be the system install. After booting your specs though, you would like to use the current directory version of MoonScript to the test

Because by default Busted will have the system install take precedence over the loaded version, running require "moonscript.base" within a test you won't get the working directory version of the code that you should be testing.

The with_dev spec helper will ensure that any require calls within the spec that ask for MoonScript modules. with_dev calls a setup and teardown that replaces _G.require with a custom version.

You'll use it like this:

import with_dev from require "spec.helpers"
describe "moonscript.base", ->
  with_dev!

  it "should load code", ->
    -- the local version is loaded
    moonscript = require "moonscript"
    moonscript.load "print 12"

Note that with_dev's require function will not use the MoonLoader, it will only load the .lua files in the working directory directory, not the moon ones. This means you must compile the working directory version of MoonScript before running the tests.

There is a make task to conveniently do all of this:

make test

Building syntax tests

The test suite has a series of syntax tests (spec/lang_spec.moon) that consist of a bunch of .moon files and their expected output. These files should capture a large range of syntax that can be verified to have the correct output when you make changes to the language.

If you are adding new syntax, or changing the expected output, then these tests will fail until you rebuild the expected outputs. You can do this by running the syntax test suite with the BUILD environment variable set.

There is a make task to conveniently do this:

make build_test_outputs

Performance timing

The syntax specs have performance timing collection built in. To get these times run the test suite with the TIME environment variable set.

TIME=1 busted spec/lang_spec.moon

Any changes to the compiler should not introduce any substantial performance decreases.