refactor: move tests folder structure and update pytest commands (#2785)

* refactor: move tests folder to src/backend

* chore(Makefile): update pytest commands to run tests from the correct directory paths for unit and integration tests

* refactor: update file path in test_custom_component.py

The file path in the test_custom_component.py file has been updated to use the correct relative path to the component_multiple_outputs.py file. This change ensures that the test code can access the correct file and improves the reliability of the test.

src/backend/tests/integration/utils.py

@@ -0,0 +1,35 @@
+import os
+from typing import List
+
+from langflow.field_typing import Embeddings
+
+
+def check_env_vars(*vars):
+    """
+    Check if all specified environment variables are set.
+
+    Args:
+    *vars (str): The environment variables to check.
+
+    Returns:
+    bool: True if all environment variables are set, False otherwise.
+    """
+    return all(os.getenv(var) for var in vars)
+
+
+class MockEmbeddings(Embeddings):
+    def __init__(self):
+        self.embedded_documents = None
+        self.embedded_query = None
+
+    @staticmethod
+    def mock_embedding(text: str):
+        return [len(text) / 2, len(text) / 5, len(text) / 10]
+
+    def embed_documents(self, texts: List[str]) -> List[List[float]]:
+        self.embedded_documents = texts
+        return [self.mock_embedding(text) for text in texts]
+
+    def embed_query(self, text: str) -> List[float]:
+        self.embedded_query = text
+        return self.mock_embedding(text)