Add more tests for zntrack.apply (#800)

* write test for issue with `zntrack.apply` can not pickle local object #799

* add assertions

* more testing

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/integration/test_apply.py

@@ -26,3 +26,36 @@ def test_apply(proj_path, eager) -> None:
     assert a.outs == ["a", "b"]
     assert b.outs == "a-b"
     assert c.outs == "a-b-c"
+
+
+@pytest.mark.parametrize("attribute", [True, False])
+@pytest.mark.parametrize("eager", [True, False])
+def test_deps_apply(proj_path, eager, attribute):
+    """Test connecting applied nodes to other nodes."""
+
+    project = zntrack.Project()
+
+    JoinedParamsToOuts = zntrack.apply(zntrack.examples.ParamsToOuts, "join")
+
+    assert issubclass(JoinedParamsToOuts, zntrack.Node)
+
+    with project:
+        a = zntrack.examples.ParamsToOuts(params=["a", "b"])
+        b = JoinedParamsToOuts(params=["a", "b"])
+        c = zntrack.apply(zntrack.examples.ParamsToOuts, "join")(params=["a", "b", "c"])
+
+        if attribute:
+            x3 = zntrack.examples.AddNodeAttributes(a=b.outs, b=c.outs)
+        else:
+            x3 = zntrack.examples.AddNodes2(a=b, b=c)
+
+    project.run(eager=eager)
+
+    x3.load()
+
+    assert isinstance(a, zntrack.Node)
+    assert isinstance(b, zntrack.Node)
+    assert isinstance(c, zntrack.Node)
+    assert isinstance(x3, zntrack.Node)
+
+    assert x3.c == "a-ba-b-c"

zntrack/examples/__init__.py

@@ -87,6 +87,18 @@ def run(self):
         self.c = self.a.c + self.b.c
 
 
+class AddNodes2(zntrack.Node):
+    """Add two nodes."""
+
+    a: AddNumbers = zntrack.deps()
+    b: AddNumbers = zntrack.deps()
+    c = zntrack.outs()
+
+    def run(self):
+        """Add two nodes."""
+        self.c = self.a.outs + self.b.outs
+
+
 class AddNodeAttributes(zntrack.Node):
     """Add two node attributes."""