Booleans: when the last-resort nudge fails both ways, try two more screw axes (#1490) (#1527)

Thanks @erkexzcx.

crates/engine/src/tests/pleat_join.rs

@@ -0,0 +1,47 @@
+//! #1490: the owner's shelled battery case (`battery-tpu-case-v2.solidcraft`, format 21, saved
+//! at `wall = 2.5 mm`) with a pleat loft joined into a window in one end wall. The loft stands on
+//! the case's open rim and its end strips lie in the wall's inner face. At walls of 2.4–2.6 mm
+//! the join failed with "no result": every exact route was refused, and the last resort's
+//! nudge failed both ways about its one screw axis. The other screws are now tried too.
+
+use std::path::Path;
+
+use serde_json::json;
+
+use super::run;
+use crate::Session;
+
+fn open() -> Session {
+    let path = Path::new(env!("CARGO_MANIFEST_DIR")).join("src/tests/fixtures/battery-tpu-case-v2.solidcraft");
+    let mut s = Session::default();
+    run(&mut s, "doc.open", json!({"path": path.to_string_lossy()}));
+    s
+}
+
+fn errors(s: &Session) -> Vec<(String, String)> {
+    s.model.results.iter().filter_map(|r| Some((r.name.clone(), r.error.clone()?))).collect()
+}
+
+fn case_volume(s: &mut Session) -> f64 {
+    let m = run(s, "inspect.measure", json!({"bodies": ["Case"]}));
+    m["total"]["volume_mm3"].as_f64().unwrap()
+}
+
+/// The design rebuilds as saved, and at 2.4 and 2.6 mm, with both pleats and every round; the
+/// case grows with the wall between them.
+#[test]
+fn the_pleats_join_at_every_wall_from_2_4_to_2_6_mm() {
+    let mut s = open();
+    assert_eq!(errors(&s), Vec::new(), "as saved, at 2.5 mm");
+    let at = case_volume(&mut s);
+    let mut volumes = Vec::new();
+    for wall in ["2.4 mm", "2.6 mm"] {
+        run(&mut s, "parameters.change", json!({"name": "wall", "expression": wall}));
+        assert_eq!(errors(&s), Vec::new(), "at {wall}");
+        volumes.push(case_volume(&mut s));
+    }
+    // About 14.8 cm³ of wall per tenth of a millimetre here.
+    let (thin, thick) = (volumes[0], volumes[1]);
+    assert!(thin < at && at < thick, "{thin} < {at} < {thick}");
+    assert!(((at - thin) - (thick - at)).abs() < 0.01 * (thick - thin), "{thin} {at} {thick}");
+}