From 9614a1a0cfad97a4158f733beb902b03d08c1e66 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20V=C3=B6lcker?= <simon.voelcker@frequenz.com>
Date: Thu, 7 May 2026 15:50:31 +0200
Subject: [PATCH] Add tests for steam boilers
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Signed-off-by: Simon Völcker <simon.voelcker@frequenz.com>
---
 tests/test_formula_preferences.py       | 28 ++++++++++++++++++------
 tests/test_microgrid_component_graph.py | 29 +++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/tests/test_formula_preferences.py b/tests/test_formula_preferences.py
index 5013cec..bc699f6 100644
--- a/tests/test_formula_preferences.py
+++ b/tests/test_formula_preferences.py
@@ -32,6 +32,7 @@
     LiIonBattery,
     Meter,
     SolarInverter,
+    SteamBoiler,
     WindTurbine,
 )
 
@@ -144,6 +145,20 @@ def _ev_graph(
     )
 
 
+def _steam_boiler_graph(
+    config: ComponentGraphConfig | None = None,
+) -> ComponentGraph[Any, Any, Any]:
+    return ComponentGraph(
+        components={
+            _grid(),
+            _meter(),
+            SteamBoiler(id=ComponentId(3), microgrid_id=_MGRID),
+        },
+        connections={_conn(1, 2), _conn(2, 3)},
+        config=config or ComponentGraphConfig(),
+    )
+
+
 _CATEGORIES = [
     pytest.param(_pv_graph, "pv_formula", "prefer_meters_in_pv_formula", id="pv"),
     pytest.param(
@@ -165,6 +180,12 @@ def _ev_graph(
         "prefer_meters_in_ev_charger_formula",
         id="ev_charger",
     ),
+    pytest.param(
+        _steam_boiler_graph,
+        "steam_boiler_formula",
+        "prefer_meters_in_steam_boiler_formula",
+        id="steam_boiler",
+    ),
 ]
 
 
@@ -217,13 +238,6 @@ def test_override_false_wins_over_global_true(
     assert formula == _DEVICE_PRIMARY
 
 
-# `steam_boiler_formula` cannot be exercised end-to-end because the
-# upstream `frequenz.client.microgrid` Python package does not currently
-# expose a `SteamBoiler` component class, so a graph that contains a
-# steam boiler cannot be constructed from Python yet. The argument-handling
-# edge cases are still meaningful and worth pinning down.
-
-
 def _empty_graph() -> ComponentGraph[Any, Any, Any]:
     return ComponentGraph(
         components={_grid(), _meter()},
diff --git a/tests/test_microgrid_component_graph.py b/tests/test_microgrid_component_graph.py
index 9f7cbff..7d6c301 100644
--- a/tests/test_microgrid_component_graph.py
+++ b/tests/test_microgrid_component_graph.py
@@ -154,6 +154,35 @@ def test_wind_turbine_graph() -> None:
     }
 
 
+def test_steam_boiler_graph() -> None:
+    """Test graph creation and formula generation for Steam Boilers."""
+    graph: microgrid_component_graph.ComponentGraph[
+        Component, ComponentConnection, ComponentId
+    ] = microgrid_component_graph.ComponentGraph(
+        components={
+            GridConnectionPoint(
+                id=ComponentId(1),
+                microgrid_id=MicrogridId(1),
+                rated_fuse_current=100,
+            ),
+            Meter(id=ComponentId(2), microgrid_id=MicrogridId(1)),
+            SteamBoiler(id=ComponentId(3), microgrid_id=MicrogridId(1)),
+        },
+        connections={
+            ComponentConnection(source=ComponentId(1), destination=ComponentId(2)),
+            ComponentConnection(source=ComponentId(2), destination=ComponentId(3)),
+        },
+    )
+
+    assert graph.components(matching_types=SteamBoiler) == {
+        SteamBoiler(id=ComponentId(3), microgrid_id=MicrogridId(1))
+    }
+    assert (
+        graph.steam_boiler_formula(steam_boiler_ids={ComponentId(3)})
+        == "COALESCE(#2, #3, 0.0)"
+    )
+
+
 def test_relay_is_passthrough() -> None:
     """`Relay` maps to cg's `Breaker`, a pass-through category.