Macro expect

macro_rules! expect {
    [$data:literal] => { ... };
    [[$data:literal]] => { ... };
    [] => { ... };
    [[]] => { ... };
}

Creates an instance of Expect from string literal:

expect![["
    Foo { value: 92 }
"]];
expect![r#"{"Foo": 92}"#];

Leading indentation is stripped.