wasmer/lib/wasi-tests/tests/wasitests/_common.rs

macro_rules! assert_wasi_output {
    ($file:expr, $name:expr, $po_dir_args: expr, $mapdir_args:expr, $envvar_args:expr, $expected:expr) => {{
        use wasmer_dev_utils::stdio::StdioCapturer;
        use wasmer_runtime::Func;
        use wasmer_wasi::generate_import_object;
        let wasm_bytes = include_bytes!($file);

        let module = wasmer_runtime::compile(&wasm_bytes[..]).expect("WASM can't be compiled");

        let import_object = generate_import_object(vec![], vec![], $po_dir_args, $mapdir_args);

        let instance = module
            .instantiate(&import_object)
            .map_err(|err| format!("Can't instantiate the WebAssembly module: {:?}", err))
            .unwrap(); // NOTE: Need to figure what the unwrap is for ??

        let capturer = StdioCapturer::new();

        let start: Func<(), ()> = instance
            .func("_start")
            .map_err(|e| format!("{:?}", e))
            .expect("start function in wasi module");

        start.call().expect("execute the wasm");

        let output = capturer.end().unwrap().0;
        let expected_output = include_str!($expected);

        assert!(
            output.contains(expected_output),
            "Output: `{}` does not contain expected output: `{}`",
            output,
            expected_output
        );
    }};
}