Test cases are in md_cases/ and are defined by toml files with the following format:

[given]
md = '''
Some input markdown
'''

[expect."test case name"]
cli_args = ["arguments", "passed", "to", "cli"]
output = '''
The expected output
'''

[expect."another text case"]
# ...

build.rs compiles these into test functions that construct an integ_test::Case and invoke its fn check. Each file becomes a mod, and each case becomes a test fn within that mod.