code: def test_fcp():
      """Tests for the FCP function."""
  
      predictions = [
          pred(0, 0, u0="u1"),
          pred(1, 1, u0="u1"),
          pred(2, 2, u0="u2"),
          pred(100, 100, u0="u2"),
      ]
      assert fcp(predictions) == 1
  
      predictions = [pred(0, 0, u0="u1"), pred(0, 0, u0="u1")]
      with pytest.raises(ValueError):
          fcp(predictions)
  
      predictions = [pred(0, 0, u0="u1")]
      with pytest.raises(ValueError):
          fcp(predictions)
  
      predictions = [
          pred(0, 1, u0="u1"),
          pred(1, 0, u0="u1"),
          pred(2, 0.5, u0="u2"),
          pred(0, 0.6, u0="u2"),
      ]
      assert fcp(predictions) == 0
  
      with pytest.raises(ValueError):
          fcp([])
  
imports: from math import sqrt
  import pytest
  from surprise.accuracy import fcp, mae, mse, rmse
label_desc: Use image node_id 4 for calling a global function with example usage: test_fcp() without return types