Add config output tests

Author: amas0

test/test_cmdstan_args.py

@@ -808,3 +808,15 @@ def test_args_pathfinder_bad(arg: str, require_int: bool) -> None:
         args = PathfinderArgs(**{arg: 1.1})  # type: ignore
         with pytest.raises(ValueError):
             args.validate()
+
+
+def test_save_cmdstan_config() -> None:
+    sampler_args = SamplerArgs()
+    cmdstan_args = CmdStanArgs(
+        model_name='bernoulli',
+        model_exe='',
+        chain_ids=[1, 2, 3, 4],
+        method_args=sampler_args,
+    )
+    command = cmdstan_args.compose_command(0, csv_file="foo")
+    assert "save_cmdstan_config=1" in command

test/test_sample.py

@@ -2204,3 +2204,27 @@ def test_no_output_draws() -> None:
     mcmc = model.sample(data=data, iter_sampling=0, save_warmup=False, chains=2)
     draws = mcmc.draws()
     assert np.array_equal(draws, np.empty((0, 2, len(mcmc.column_names))))
+
+
+def test_config_output() -> None:
+    stan = os.path.join(DATAFILES_PATH, 'bernoulli.stan')
+    jdata = os.path.join(DATAFILES_PATH, 'bernoulli.data.json')
+    model = CmdStanModel(stan_file=stan)
+    fit = model.sample(
+        data=jdata,
+        chains=2,
+        seed=12345,
+        iter_warmup=100,
+        iter_sampling=200,
+    )
+    assert all(os.path.exists(cf) for cf in fit.runset.config_files)
+
+    # Config file naming differs when only a single chain is output
+    fit_one_chain = model.sample(
+        data=jdata,
+        chains=1,
+        seed=12345,
+        iter_warmup=100,
+        iter_sampling=200,
+    )
+    assert all(os.path.exists(cf) for cf in fit_one_chain.runset.config_files)