From 5d5344cf9198ac0f4342cc2e972702ad636822c8 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 9 Feb 2026 10:56:07 -0600
Subject: [PATCH] Add tests for cg.templatable() auto FlashStringLiteral
 wrapping

Cover the new automatic ESPHOME_F() wrapping behavior: static strings
with std::string output_type, non-string values, None output_type,
to_exp callable/dict, and lambda passthrough.
---
 tests/unit_tests/test_cpp_generator.py | 72 ++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/tests/unit_tests/test_cpp_generator.py b/tests/unit_tests/test_cpp_generator.py
index 84b555316f..8e24036cd0 100644
--- a/tests/unit_tests/test_cpp_generator.py
+++ b/tests/unit_tests/test_cpp_generator.py
@@ -630,3 +630,75 @@ class TestProcessLambda:
         # Test invalid tuple format (single element)
         with pytest.raises(AssertionError):
             await cg.process_lambda(lambda_obj, [(int,)])
+
+
+@pytest.mark.asyncio
+async def test_templatable__string_with_std_string_returns_flash_literal() -> None:
+    """Static string with std::string output_type returns FlashStringLiteral."""
+    result = await cg.templatable("hello", [], ct.std_string)
+
+    assert isinstance(result, cg.FlashStringLiteral)
+    assert str(result) == 'ESPHOME_F("hello")'
+
+
+@pytest.mark.asyncio
+async def test_templatable__empty_string_with_std_string() -> None:
+    """Empty static string with std::string output_type returns FlashStringLiteral."""
+    result = await cg.templatable("", [], ct.std_string)
+
+    assert isinstance(result, cg.FlashStringLiteral)
+    assert str(result) == 'ESPHOME_F("")'
+
+
+@pytest.mark.asyncio
+async def test_templatable__string_with_none_output_type() -> None:
+    """Static string with output_type=None returns raw string (no wrapping)."""
+    result = await cg.templatable("hello", [], None)
+
+    assert isinstance(result, str)
+    assert result == "hello"
+
+
+@pytest.mark.asyncio
+async def test_templatable__int_with_std_string() -> None:
+    """Non-string value with std::string output_type returns raw value."""
+    result = await cg.templatable(42, [], ct.std_string)
+
+    assert result == 42
+
+
+@pytest.mark.asyncio
+async def test_templatable__string_with_non_string_output_type() -> None:
+    """Static string with non-std::string output_type returns raw string."""
+    result = await cg.templatable("hello", [], ct.bool_)
+
+    assert isinstance(result, str)
+    assert result == "hello"
+
+
+@pytest.mark.asyncio
+async def test_templatable__with_to_exp_callable() -> None:
+    """When to_exp is provided, it is applied to non-template values."""
+    result = await cg.templatable(42, [], None, to_exp=lambda x: x * 2)
+
+    assert result == 84
+
+
+@pytest.mark.asyncio
+async def test_templatable__with_to_exp_dict() -> None:
+    """When to_exp is a dict, value is looked up."""
+    mapping: dict[str, int] = {"on": 1, "off": 0}
+    result = await cg.templatable("on", [], None, to_exp=mapping)
+
+    assert result == 1
+
+
+@pytest.mark.asyncio
+async def test_templatable__lambda_with_std_string() -> None:
+    """Lambda value returns LambdaExpression, not FlashStringLiteral."""
+    from esphome.core import Lambda
+
+    lambda_obj = Lambda('return "hello";')
+    result = await cg.templatable(lambda_obj, [], ct.std_string)
+
+    assert isinstance(result, cg.LambdaExpression)