bug: can't assert_eq against "\n"

[xiyuzhai]

update expect wouldn't result in a valid expect for just one single line.

#[test]
fn it_doesnt_work() {
    use expect_test::expect;
    use expect_test::Expect;

    fn t(expect: &Expect) {
        expect.assert_eq("\n")
    }
    t(&expect![[r#"

    "#]]);
}

Basically, when UPDATE_EXPECT=1 cargo test, the tests would pass. But then without the env, cargo test would fail.

See https://github.com/xiyuzhai/expect-test-bug for a minimal example.

Run

make test

to get the error.