diff --git a/pyproject.toml b/pyproject.toml
index a0ee6a8..77c6d1a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -2,3 +2,5 @@
 asyncio_mode = "auto"
 testpaths = ["tests"]
 norecursedirs = [".git"]
+log_format = "%(asctime)s.%(msecs)03d %(levelname)-8s %(threadName)s %(name)s:%(filename)s:%(lineno)s %(message)s"
+log_date_format = "%Y-%m-%d %H:%M:%S"
diff --git a/tests/const.py b/tests/const.py
new file mode 100644
index 0000000..9ae9c94
--- /dev/null
+++ b/tests/const.py
@@ -0,0 +1,36 @@
+"""Test constants."""
+
+HOME_CONFIG = {"unique_id": "home"}
+
+NY_LOC = {
+    "latitude": 40.68954412564642,
+    "longitude": -74.04486696480146,
+    "elevation": 0,
+    "time_zone": "America/New_York",
+}
+NY_CONFIG = {
+    "unique_id": "new_york",
+    "location": "Statue of Liberty",
+} | NY_LOC
+
+TWINE_LOC = {
+    "latitude": 39.50924426436838,
+    "longitude": -98.43369506033378,
+    "elevation": 10,
+    "time_zone": "America/Chicago",
+}
+TWINE_CONFIG = {
+    "unique_id": "twine",
+    "location": "World's Largest Ball of Twine",
+} | TWINE_LOC
+
+HW_LOC = {
+    "latitude": 34.134092337996336,
+    "longitude": -118.32154780135669,
+    "elevation": 391,
+    "time_zone": "America/Los_Angeles",
+}
+HW_CONFIG = {
+    "unique_id": "hollywood",
+    "location": "Hollywood Sign",
+} | HW_LOC
diff --git a/tests/test_binary_sensor.py b/tests/test_binary_sensor.py
new file mode 100644
index 0000000..75f641b
--- /dev/null
+++ b/tests/test_binary_sensor.py
@@ -0,0 +1,87 @@
+"""Test binary_sensor module."""
+from __future__ import annotations
+
+from datetime import datetime, time, timedelta
+from unittest.mock import patch
+import pytest
+
+from pytest_homeassistant_custom_component.common import (
+    async_fire_time_changed,
+    assert_setup_component,
+)
+
+from homeassistant.const import STATE_OFF, STATE_ON
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers.entity_registry import EntityRegistry
+from homeassistant.setup import async_setup_component
+from homeassistant.util import dt as dt_util, slugify
+
+from custom_components.sun2.const import DOMAIN
+
+from .const import NY_CONFIG
+
+
+@pytest.mark.parametrize(
+    "elevation,name,slug",
+    (
+        ("horizon", None, "above_horizon"),
+        (1, None, "above_1_0_deg"),
+        (-1, None, "above_minus_1_0_deg"),
+        (0, "Name Test", "name_test"),
+    ),
+)
+async def test_yaml_binary_sensor(
+    hass: HomeAssistant,
+    entity_registry: EntityRegistry,
+    elevation: str | float,
+    name: str | None,
+    slug: str,
+) -> None:
+    """Test YAML configured elevation binary sensor."""
+    config = NY_CONFIG | {
+        "binary_sensors": [
+            {
+                "unique_id": "bs1",
+                "elevation": elevation,
+            }
+        ]
+    }
+    if name:
+        config["binary_sensors"][0]["name"] = name
+
+    tz = dt_util.get_time_zone(NY_CONFIG["time_zone"])
+    base_time = dt_util.now(tz)
+
+    # Set time to 00:00:00 tommorow.
+    now = datetime.combine((base_time + timedelta(1)).date(), time()).replace(tzinfo=tz)
+
+    with patch("homeassistant.util.dt.now", return_value=now):
+        with assert_setup_component(1, DOMAIN):
+            await async_setup_component(hass, DOMAIN, {DOMAIN: [config]})
+        await hass.async_block_till_done()
+
+    config_entry = hass.config_entries.async_entries(DOMAIN)[0]
+
+    # Check that elevation binary_sensor was created with expected entity ID and it has
+    # the expected state.
+    entity_id = entity_registry.async_get_entity_id(
+        "binary_sensor", DOMAIN, f"{config_entry.entry_id}-bs1"
+    )
+    expected_id = f"binary_sensor.{slugify(NY_CONFIG['location'])}_sun_{slug}"
+    assert entity_id == expected_id
+    state = hass.states.get(entity_id)
+    # Sun is always below the horizon at midnight in New York.
+    assert state.state == STATE_OFF
+    # And is always above the horizon at noon.
+    # Next change should be after midnight and before noon.
+    next_change = state.attributes.get("next_change")
+    noon = now.replace(hour=12)
+    assert isinstance(next_change, datetime)
+    assert now < next_change < noon
+
+    # Move time to next_change and make sure state has changed.
+    with patch("homeassistant.util.dt.now", return_value=next_change):
+        async_fire_time_changed(hass, next_change)
+        await hass.async_block_till_done()
+    state = hass.states.get(entity_id)
+    assert state.state == STATE_ON
diff --git a/tests/test_init.py b/tests/test_init.py
index 7305b45..6877d0b 100644
--- a/tests/test_init.py
+++ b/tests/test_init.py
@@ -1,3 +1,4 @@
+"""Test init module."""
 from __future__ import annotations
 
 from unittest.mock import patch
@@ -11,40 +12,7 @@
 
 from custom_components.sun2.const import DOMAIN
 
-CONFIG_1 = {"unique_id": "1"}
-
-LOC_2A = {
-    "latitude": 40.68954412564642,
-    "longitude": -74.04486696480146,
-    "elevation": 0,
-    "time_zone": "America/New_York",
-}
-CONFIG_2A = {
-    "unique_id": "Test 2",
-    "location": "Statue of Liberty",
-} | LOC_2A
-
-LOC_2B = {
-    "latitude": 39.50924426436838,
-    "longitude": -98.43369506033378,
-    "elevation": 10,
-    "time_zone": "America/Chicago",
-}
-CONFIG_2B = {
-    "unique_id": "Test 2",
-    "location": "World's Largest Ball of Twine",
-} | LOC_2B
-
-LOC_3 = {
-    "latitude": 34.134092337996336,
-    "longitude": -118.32154780135669,
-    "elevation": 391,
-    "time_zone": "America/Los_Angeles",
-}
-CONFIG_3 = {
-    "unique_id": "3",
-    "location": "Hollywood Sign",
-} | LOC_3
+from .const import HOME_CONFIG, HW_CONFIG, HW_LOC, NY_CONFIG, NY_LOC, TWINE_CONFIG, TWINE_LOC
 
 
 async def test_basic_yaml_config(
@@ -52,7 +20,7 @@ async def test_basic_yaml_config(
 ) -> None:
     """Test basic YAML configuration."""
     with assert_setup_component(1, DOMAIN):
-        await async_setup_component(hass, DOMAIN, {DOMAIN: [CONFIG_1]})
+        await async_setup_component(hass, DOMAIN, {DOMAIN: [HOME_CONFIG]})
     await hass.async_block_till_done()
 
     expected_entities = (
@@ -104,11 +72,9 @@ async def test_basic_yaml_config(
             assert entry.disabled != enabled
 
 
-async def test_reload_service(
-    hass: HomeAssistant, entity_registry: EntityRegistry
-) -> None:
+async def test_reload_service(hass: HomeAssistant) -> None:
     """Test basic YAML configuration."""
-    init_config = [CONFIG_1, CONFIG_2A]
+    init_config = [HOME_CONFIG, NY_CONFIG]
     with assert_setup_component(len(init_config), DOMAIN):
         await async_setup_component(hass, DOMAIN, {DOMAIN: init_config})
     await hass.async_block_till_done()
@@ -117,19 +83,19 @@ async def test_reload_service(
     config_entries = hass.config_entries.async_entries(DOMAIN)
     assert len(config_entries) == 2
     config_entry_1 = config_entries[0]
-    assert config_entry_1.unique_id == CONFIG_1["unique_id"]
+    assert config_entry_1.unique_id == HOME_CONFIG["unique_id"]
     assert config_entry_1.title == hass.config.location_name
     assert config_entry_1.options == {}
     config_entry_2 = config_entries[1]
-    assert config_entry_2.unique_id == CONFIG_2A["unique_id"]
-    assert config_entry_2.title == CONFIG_2A["location"]
-    assert config_entry_2.options == LOC_2A
+    assert config_entry_2.unique_id == NY_CONFIG["unique_id"]
+    assert config_entry_2.title == NY_CONFIG["location"]
+    assert config_entry_2.options == NY_LOC
 
     # Check reload service exists.
     assert hass.services.has_service(DOMAIN, "reload")
 
     # Reload new config.
-    reload_config = [CONFIG_2B, CONFIG_3]
+    reload_config = [TWINE_CONFIG, HW_CONFIG]
     with patch(
         "custom_components.sun2.async_integration_yaml_config",
         autospec=True,
@@ -142,16 +108,16 @@ async def test_reload_service(
     config_entries = hass.config_entries.async_entries(DOMAIN)
     assert len(config_entries) == 2
     config_entry_1 = config_entries[0]
-    assert config_entry_1.unique_id == CONFIG_2B["unique_id"]
-    assert config_entry_1.title == CONFIG_2B["location"]
-    assert config_entry_1.options == LOC_2B
+    assert config_entry_1.unique_id == TWINE_CONFIG["unique_id"]
+    assert config_entry_1.title == TWINE_CONFIG["location"]
+    assert config_entry_1.options == TWINE_LOC
     config_entry_2 = config_entries[1]
-    assert config_entry_2.unique_id == CONFIG_3["unique_id"]
-    assert config_entry_2.title == CONFIG_3["location"]
-    assert config_entry_2.options == LOC_3
+    assert config_entry_2.unique_id == HW_CONFIG["unique_id"]
+    assert config_entry_2.title == HW_CONFIG["location"]
+    assert config_entry_2.options == HW_LOC
 
     # Reload with same config.
-    reload_config = [CONFIG_2B, CONFIG_3]
+    reload_config = [TWINE_CONFIG, HW_CONFIG]
     with patch(
         "custom_components.sun2.async_integration_yaml_config",
         autospec=True,
@@ -192,9 +158,7 @@ async def test_reload_service(
     assert not hass.config_entries.async_entries(DOMAIN)
 
 
-async def test_ha_config_update(
-    hass: HomeAssistant, entity_registry: EntityRegistry
-) -> None:
+async def test_ha_config_update(hass: HomeAssistant) -> None:
     """Test when HA config is updated."""
     new_time_zone = "America/New_York"
     new_location_name = "New York, NY"
@@ -203,7 +167,7 @@ async def test_ha_config_update(
     assert hass.config.time_zone != new_time_zone
     assert hass.config.location_name != new_location_name
 
-    await async_setup_component(hass, DOMAIN, {DOMAIN: [CONFIG_1]})
+    await async_setup_component(hass, DOMAIN, {DOMAIN: [HOME_CONFIG]})
     await hass.async_block_till_done()
 
     # ConfigEntry object may change values, but it should not be replaced by a new
@@ -237,7 +201,7 @@ async def test_ha_config_update(
     with patch(
         "custom_components.sun2.async_integration_yaml_config",
         autospec=True,
-        return_value={DOMAIN: [CONFIG_1]},
+        return_value={DOMAIN: [HOME_CONFIG]},
     ):
         await hass.config.async_update(location_name=new_location_name)
         await hass.async_block_till_done()