Feature/component test fixture (#1142)

tests/component_tests/conftest.py

@@ -0,0 +1,23 @@
+""" Fixtures for component tests """
+
+import pytest
+
+from esphome.core import CORE
+from esphome.config import read_config
+from esphome.__main__ import generate_cpp_contents
+
+
+@pytest.fixture
+def generate_main():
+    """ Generates the C++ main.cpp file and returns it in string form """
+
+    def generator(path: str) -> str:
+        CORE.config_path = path
+        CORE.config = read_config({})
+        generate_cpp_contents(CORE.config)
+        print(CORE.cpp_main_section)
+        return CORE.cpp_main_section
+
+    yield generator
+
+    CORE.reset()