ignore a few tests that run slowly in miri

src/tests/iter.rs

@@ -3,6 +3,7 @@ use super::*;
 use crate::Flags;
 
 #[test]
+#[cfg(not(miri))] // Very slow in miri
 fn roundtrip() {
     for a in 0u8..=255 {
         for b in 0u8..=255 {

src/tests/parser.rs

@@ -6,6 +6,7 @@ use crate::{
 };
 
 #[test]
+#[cfg(not(miri))] // Very slow in miri
 fn roundtrip() {
     let mut s = String::new();
 

tests/compile.rs

@@ -2,13 +2,15 @@
 // an impossible build between error messages emitted on various channels.
 // Since https://github.com/dtolnay/trybuild/pull/170 we always need to have a
 // `stderr` file for each test so we can't simply ignore the output on different channels.
+#[cfg(not(miri))]
 #[rustversion::attr(beta, test)]
 #[allow(dead_code)]
 fn fail() {
     let t = trybuild::TestCases::new();
     t.compile_fail("tests/compile-fail/**/*.rs");
 }
 
+#[cfg(not(miri))]
 #[test]
 fn pass() {
     let t = trybuild::TestCases::new();