update cargo miri test to test rng crate a bit; this currently fails

test-cargo-miri/run-test.py

@@ -43,7 +43,7 @@ def test_cargo_miri_run():
     )
 
 def test_cargo_miri_test():
-    test("cargo miri test", ["cargo", "miri", "test", "-q"], "test.stdout.ref", "test.stderr.ref")
+    test("cargo miri test", ["cargo", "miri", "test", "-q", "--", "-Zmiri-seed=feed"], "test.stdout.ref", "test.stderr.ref")
     test("cargo miri test (with filter)",
         ["cargo", "miri", "test", "-q", "--", "--", "impl"],
         "test.stdout.ref2", "test.stderr.ref"

test-cargo-miri/test.stdout.ref

@@ -5,9 +5,10 @@ test test::rng ... ok
 test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
 
 
-running 2 tests
+running 3 tests
 test rng ... ok
+test seeded_rng ... ok
 test simple ... ok
 
-test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
+test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
 

test-cargo-miri/tests/test.rs

@@ -1,6 +1,6 @@
 extern crate rand;
 
-use rand::{Rng, SeedableRng};
+use rand::{SeedableRng, FromEntropy, Rng, rngs::SmallRng};
 
 #[test]
 fn simple() {
@@ -17,6 +17,14 @@ fn rng() {
     assert_ne!(x, y);
 }
 
+#[test]
+#[cfg(not(target_os="macos"))] // FIXME entropy does not work on macOS
+fn seeded_rng() {
+    // Use this opportunity to test querying the RNG (needs an external crate, hence tested here and not in the compiletest suite)
+    let mut rng = SmallRng::from_entropy();
+    let _val = rng.gen::<i32>();
+}
+
 // A test that won't work on miri
 #[cfg(not(miri))]
 #[test]