Ensure nChains is greater than 1 (RascalSoftware#141)

* Change nChains to be greater than 1

* fixed tests

Author: alexhroom

RATapi/controls.py

@@ -118,7 +118,7 @@ class Controls(BaseModel, validate_assignment=True, extra="forbid", use_attribut
     nSamples: int = Field(20000, ge=0)
     """[DREAM] The number of samples in the initial population for each chain."""
 
-    nChains: int = Field(10, gt=0)
+    nChains: int = Field(10, gt=1)
     """[DREAM] The number of Markov chains to use in the algorithm."""
 
     jumpProbability: float = Field(0.5, gt=0.0, lt=1.0)

tests/test_controls.py

@@ -859,7 +859,7 @@ def test_dream_nSamples_error(self, value: int) -> None:
     @pytest.mark.parametrize("value", [-5, 0])
     def test_dream_nChains_error(self, value: int) -> None:
         """Tests the nChains setter error in Dream class."""
-        with pytest.raises(pydantic.ValidationError, match="Input should be greater than 0"):
+        with pytest.raises(pydantic.ValidationError, match="Input should be greater than 1"):
             self.dream.nChains = value
 
     def test_control_class_dream_str(self, table_str) -> None: