Test for callback streams

src/machine/lib_machine/tests.rs

@@ -1,5 +1,8 @@
+use std::{cell::RefCell, io::Read, rc::Rc};
+use std::io::Write;
+
 use super::*;
-use crate::MachineBuilder;
+use crate::{MachineBuilder, StreamConfig};
 
 #[test]
 #[cfg_attr(miri, ignore = "it takes too long to run")]
@@ -608,3 +611,33 @@ fn errors_and_exceptions() {
         [Ok(LeafAnswer::Exception(Term::atom("a")))]
     );
 }
+
+#[test]
+#[cfg_attr(miri, ignore)]
+fn callback_streams() {
+    let test_string = Rc::new(RefCell::new(String::new()));
+    let test_string2 = test_string.clone();
+
+    let (mut user_input, streams) = StreamConfig::with_callbacks(
+       Some(Box::new(move |x| { x.read_to_string(&mut *test_string2.borrow_mut()).unwrap(); })),
+       None
+    );
+    let mut machine = MachineBuilder::default().with_streams(streams).build();
+
+    write!(&mut user_input, "a(1,2,3).").unwrap();
+
+    let complete_answer: Vec<_> = machine.run_query("read(A), write('asdf'), nl, flush_output.").collect();
+
+    assert_eq!(
+        complete_answer,
+        [Ok(LeafAnswer::from_bindings([
+            ("A", Term::compound("a", [
+                 Term::integer(1),
+                 Term::integer(2),
+                 Term::integer(3)
+            ])),
+        ]))]
+    );
+
+    assert_eq!(*test_string.borrow(), "asdf\n");
+}