diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/conftest.py b/tests/conftest.py
index 0451ea7..48a7eb7 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import dataclasses
 import typing as t
 
 import pytest
@@ -7,10 +8,17 @@
 from htpy import Node, iter_node
 
 if t.TYPE_CHECKING:
-    from collections.abc import Generator
+    from collections.abc import Callable, Generator
 
 
-RenderFixture: t.TypeAlias = t.Callable[[Node], list[str]]
+@dataclasses.dataclass(frozen=True)
+class Trace:
+    description: str
+
+
+RenderResult: t.TypeAlias = list[str | Trace]
+RenderFixture: t.TypeAlias = t.Callable[[Node], RenderResult]
+TraceFixture: t.TypeAlias = t.Callable[[str], None]
 
 
 @pytest.fixture(scope="session")
@@ -28,13 +36,33 @@ def django_env() -> None:
 
 
 @pytest.fixture
-def render() -> Generator[RenderFixture, None, None]:
+def render_result() -> RenderResult:
+    return []
+
+
+@pytest.fixture
+def trace(render_result: RenderResult) -> Callable[[str], None]:
+    def func(description: str) -> None:
+        render_result.append(Trace(description=description))
+
+    return func
+
+
+@pytest.fixture
+def render(render_result: RenderResult) -> Generator[RenderFixture, None, None]:
     called = False
 
-    def func(node: Node) -> list[str]:
+    def func(node: Node) -> RenderResult:
         nonlocal called
+
+        if called:
+            raise AssertionError("render() must only be called once per test")
+
         called = True
-        return list(iter_node(node))
+        for chunk in iter_node(node):
+            render_result.append(chunk)
+
+        return render_result
 
     yield func
 
diff --git a/tests/test_attributes.py b/tests/test_attributes.py
index e833bdc..b0c5e70 100644
--- a/tests/test_attributes.py
+++ b/tests/test_attributes.py
@@ -178,14 +178,16 @@ def test_attrs_and_kwargs(render: RenderFixture) -> None:
     assert render(result) == ['<div a="1" for="b" b="2">', "</div>"]
 
 
-def test_class_priority(render: RenderFixture) -> None:
-    result = div(".a", {"class": "b"}, class_="c")
-    assert render(result) == ['<div class="c">', "</div>"]
-
+def test_class_priority_dict(render: RenderFixture) -> None:
     result = div(".a", {"class": "b"})
     assert render(result) == ['<div class="b">', "</div>"]
 
 
+def test_class_priority_dict_and_kwarg(render: RenderFixture) -> None:
+    result = div(".a", {"class": "b"}, class_="c")
+    assert render(result) == ['<div class="c">', "</div>"]
+
+
 def test_attribute_priority(render: RenderFixture) -> None:
     result = div({"foo": "a"}, foo="b")
     assert render(result) == ['<div foo="b">', "</div>"]
diff --git a/tests/test_children.py b/tests/test_children.py
index 6c2e64b..fcfb818 100644
--- a/tests/test_children.py
+++ b/tests/test_children.py
@@ -13,12 +13,14 @@
 
 from htpy import Element, VoidElement, dd, div, dl, dt, html, img, input, li, my_custom_element, ul
 
+from .conftest import Trace
+
 if t.TYPE_CHECKING:
     from collections.abc import Callable, Generator
 
     from htpy import Node
 
-    from .conftest import RenderFixture
+    from .conftest import RenderFixture, TraceFixture
 
 
 def test_void_element(render: RenderFixture) -> None:
@@ -134,29 +136,43 @@ def test_ignored(render: RenderFixture, ignored_value: t.Any) -> None:
     assert render(div[ignored_value]) == ["<div>", "</div>"]
 
 
-def test_sync_iter() -> None:
-    trace = "not started"
-
+def test_lazy_iter(render: RenderFixture, trace: TraceFixture) -> None:
     def generate_list() -> Generator[Element, None, None]:
-        nonlocal trace
-
-        trace = "before yield"
+        trace("before yield")
         yield li("#a")
+        trace("after yield")
+
+    result = render(ul[generate_list()])
+    assert result == [
+        "<ul>",
+        Trace("before yield"),
+        '<li id="a">',
+        "</li>",
+        Trace("after yield"),
+        "</ul>",
+    ]
 
-        trace = "done"
 
-    iterator = iter(ul[generate_list()])
+def test_lazy_callable(render: RenderFixture, trace: TraceFixture) -> None:
+    def parent() -> Element:
+        trace("in parent")
+        return div("#parent")[child]
 
-    assert next(iterator) == "<ul>"
-    assert trace == "not started"
+    def child() -> str:
+        trace("in child")
+        return "child"
 
-    assert next(iterator) == '<li id="a">'
-    assert trace == "before yield"
-    assert next(iterator) == "</li>"
-    assert trace == "before yield"
+    result = render(div[parent])
 
-    assert next(iterator) == "</ul>"
-    assert trace == "done"
+    assert result == [
+        "<div>",
+        Trace(description="in parent"),
+        '<div id="parent">',
+        Trace(description="in child"),
+        "child",
+        "</div>",
+        "</div>",
+    ]
 
 
 def test_iter_str(render: RenderFixture) -> None:
@@ -175,23 +191,6 @@ def test_iter_markup(render: RenderFixture) -> None:
     assert type(child) is str
 
 
-def test_callable() -> None:
-    called = False
-
-    def generate_img() -> VoidElement:
-        nonlocal called
-        called = True
-        return img
-
-    iterator = iter(div[generate_img])
-
-    assert next(iterator) == "<div>"
-    assert called is False
-    assert next(iterator) == "<img>"
-    assert called is True
-    assert next(iterator) == "</div>"
-
-
 def test_escape_children(render: RenderFixture) -> None:
     result = render(div['>"'])
     assert result == ["<div>", "&gt;&#34;", "</div>"]