improve test coverage and test cycle detection

lenskit/lenskit/pipeline/runner.py

@@ -58,6 +58,7 @@ def run(self, node: Node[Any], *, required: bool = True) -> Any:
             self._run_node(node, required)
             self.status[node.name] = "finished"
         except Exception as e:
+            _log.error("node %s failed with error %s", node, e)
             self.status[node.name] = "failed"
             raise e
 
@@ -73,7 +74,7 @@ def _run_node(self, node: Node[Any], required: bool) -> None:
                 self._run_component(name, comp, inputs, wiring)
             case FallbackNode(name, alts):
                 self._run_fallback(name, alts)
-            case _:
+            case _:  # pragma: nocover
                 raise RuntimeError(f"invalid node {node}")
 
     def _inject_input(self, name: str, types: set[type] | None, required: bool) -> None:

lenskit/tests/test_pipeline.py

@@ -140,6 +140,31 @@ def incr(msg: str) -> str:
         pipe.run(node, msg=47)
 
 
+def test_component_type_mismatch():
+    pipe = Pipeline()
+
+    def incr(msg: str) -> str:
+        return msg
+
+    node = pipe.add_component("return", incr, msg=47)
+    with raises(TypeError):
+        pipe.run(node)
+
+
+def test_component_unwired_input():
+    pipe = Pipeline()
+    msg = pipe.create_input("msg", str)
+
+    def ident(msg: str, m2: str | None) -> str:
+        if m2:
+            return msg + m2
+        else:
+            return msg
+
+    node = pipe.add_component("return", ident, msg=msg)
+    assert pipe.run(node, msg="hello") == "hello"
+
+
 def test_chain():
     pipe = Pipeline()
     x = pipe.create_input("x", int)
@@ -183,6 +208,24 @@ def add(x: int, y: int) -> int:
     assert pipe.run(nd, a=3, b=7) == 6
 
 
+def test_cycle():
+    pipe = Pipeline()
+    b = pipe.create_input("b", int)
+
+    def double(x: int) -> int:
+        return x * 2
+
+    def add(x: int, y: int) -> int:
+        return x + y
+
+    nd = pipe.add_component("double", double)
+    na = pipe.add_component("add", add, x=nd, y=b)
+    pipe.connect(nd, x=na)
+
+    with raises(RuntimeError, match="cycle"):
+        pipe.run(a=1, b=7)
+
+
 def test_replace_component():
     pipe = Pipeline()
     a = pipe.create_input("a", int)