code: def test_fstring_with_one_var():
      fstring = FString(template="Hello, {name}!", variables=["name"])
      output = fstring.run(name="Alice")
      assert output == {"string": "Hello, Alice!"}
  
imports: import pytest
  from haystack.testing.sample_components import FString
label_desc: Use image node_id 1 for calling a global function with example usage: test_fstring_with_one_var() without return types