chore: checkpoint before Python removal

vendor/psm/tests/stack_direction.rs

@@ -0,0 +1,6 @@
+extern crate psm;
+
+#[test]
+fn always_equal() {
+    assert_eq!(psm::StackDirection::new(), psm::StackDirection::new());
+}

vendor/psm/tests/stack_direction_2.rs

@@ -0,0 +1,29 @@
+extern crate psm;
+
+#[inline(never)]
+fn test_direction(previous_sp: *mut u8) {
+    let current_sp = psm::stack_pointer();
+    match psm::StackDirection::new() {
+        psm::StackDirection::Ascending => {
+            assert!(
+                current_sp > previous_sp,
+                "the stack pointer is not ascending! current = {:p}, previous = {:p}",
+                current_sp,
+                previous_sp
+            );
+        }
+        psm::StackDirection::Descending => {
+            assert!(
+                current_sp < previous_sp,
+                "the stack pointer is not descending! current = {:p}, previous = {:p}",
+                current_sp,
+                previous_sp
+            );
+        }
+    }
+}
+
+#[test]
+fn direction_right() {
+    test_direction(psm::stack_pointer());
+}