Model IO in JSON. (#5110)

tests/python/test_basic_models.py

@@ -1,6 +1,8 @@
 import numpy as np
 import xgboost as xgb
 import unittest
+import os
+import json
 
 dpath = 'demo/data/'
 dtrain = xgb.DMatrix(dpath + 'agaricus.txt.train')
@@ -200,3 +202,23 @@ class TestModels(unittest.TestCase):
         bst.predict(dm2)  # success
         self.assertRaises(ValueError, bst.predict, dm1)
         bst.predict(dm2)  # success
+
+    def test_json_model_io(self):
+        X = np.random.random((10, 3))
+        y = np.random.randint(2, size=(10,))
+
+        dm1 = xgb.DMatrix(X, y)
+        bst = xgb.train({'tree_method': 'hist'}, dm1)
+        bst.save_model('./model.json')
+
+        with open('./model.json', 'r') as fd:
+            j_model = json.load(fd)
+        assert isinstance(j_model['Learner'], dict)
+
+        bst = xgb.Booster(model_file='./model.json')
+
+        with open('./model.json', 'r') as fd:
+            j_model = json.load(fd)
+        assert isinstance(j_model['Learner'], dict)
+
+        os.remove('model.json')