Class DummyTxn

atomic-core/src/pristine/view_graph.rs:315–315

We can't easily construct a full GraphTxnT mock here, but we can test the is_visible logic directly.

        // We can't easily construct a full GraphTxnT mock here, but we can
        // test the is_visible logic directly.
        struct DummyTxn;

        let vg: ViewGraph<'_, DummyTxn> = ViewGraph {
            inner: &DummyTxn,