Harden flow advancement exit assertions

tests/test_task_flow_engine.py

@@ -64,6 +64,50 @@ def test_failing_exit_assertion_identifies_blocking_assertion():
     assert result.blocking_assertions[0].actual == ["done", "todo"]
 
 
+def test_can_reach_checks_current_exit_assertions_before_target_entry():
+    flow = FlowDef(
+        id="workstream.test",
+        entity_type="workstream",
+        workstations=[
+            WorkstationDef(
+                name="active",
+                exit_assertions=[
+                    AssertionDef(
+                        id="dependencies.all_complete",
+                        target="dependencies.*.workstation",
+                        op="all_eq",
+                        value=["finished", "archived"],
+                    )
+                ],
+            ),
+            WorkstationDef(
+                name="finished",
+                entry_assertions=[
+                    AssertionDef(
+                        id="tasks.all_done",
+                        target="tasks.*.status",
+                        op="all_eq",
+                        value=["done", "cancelled"],
+                    )
+                ],
+            ),
+        ],
+    )
+
+    can_reach, failures = FlowEngine().can_reach(
+        {
+            "status": "active",
+            "tasks": [{"status": "done"}],
+            "dependencies": [{"workstation": "active"}],
+        },
+        flow,
+        "finished",
+    )
+
+    assert can_reach is False
+    assert [item.id for item in failures] == ["dependencies.all_complete"]
+
+
 def test_custom_op_callable_is_invoked():
     calls = []