To run tests execute
$ stack test
To re-run tests on file changes execute
$ stack test --file-watch
To add a new test, create a module inside tests directory, this module should
export its tests as TestTree datatype. Then import this new module to
tests/Spec.hs, and add its tests to list of other tests in main (see
ShadowingTest for example).
The issue with symbol λ occures with encoding system different from UTF-8.
Thus, to run project on Windows machine you should set UTF-8 encoding for terminal.
Example for PowerShell:
lambda-calculus-interpreter>chcp 65001
lambda-calculus-interpreter>stack ghci