Add tests for json.dump

tests/snippets/json_snippet.py

@@ -1,5 +1,6 @@
 from testutils import assert_raises
 import json
+from io import StringIO
 
 def round_trip_test(obj):
     # serde_json and Python's json module produce slightly differently spaced
@@ -7,25 +8,54 @@ def round_trip_test(obj):
     # proxy
     return obj == json.loads(json.dumps(obj))
 
+def json_dump(obj):
+    f = StringIO()
+    json.dump(obj, f)
+    f.seek(0)
+    return f.getvalue()
+
 assert '"string"' == json.dumps("string")
+assert '"string"' == json_dump("string")
+
 assert "1" == json.dumps(1)
+assert "1" == json_dump(1)
+
 assert "1.0" == json.dumps(1.0)
+assert "1.0" == json_dump(1.0)
+
 assert "true" == json.dumps(True)
+assert "true" == json_dump(True)
+
 assert "false" == json.dumps(False)
+assert "false" == json_dump(False)
+
 assert 'null' == json.dumps(None)
+assert 'null' == json_dump(None)
 
 assert '[]' == json.dumps([])
+assert '[]' == json_dump([])
+
 assert '[1]' == json.dumps([1])
+assert '[1]' == json_dump([1])
+
 assert '[[1]]' == json.dumps([[1]])
+assert '[[1]]' == json_dump([[1]])
+
 assert round_trip_test([1, "string", 1.0, True])
 
 assert '[]' == json.dumps(())
+assert '[]' == json_dump(())
+
 assert '[1]' == json.dumps((1,))
+assert '[1]' == json_dump((1,))
+
 assert '[[1]]' == json.dumps(((1,),))
+assert '[[1]]' == json_dump(((1,),))
 # tuples don't round-trip through json
 assert [1, "string", 1.0, True] == json.loads(json.dumps((1, "string", 1.0, True)))
 
 assert '{}' == json.dumps({})
+assert '{}' == json_dump({})
 assert round_trip_test({'a': 'b'})
 
 # should reject non-str keys in jsons
@@ -49,21 +79,31 @@ assert [['a'], 'b'] == json.loads('[["a"], "b"]')
 class String(str): pass
 
 assert "string" == json.loads(String('"string"'))
+
 assert '"string"' == json.dumps(String("string"))
+assert '"string"' == json_dump(String("string"))
 
 class Int(int): pass
 class Float(float): pass
 
 assert '1' == json.dumps(Int(1))
+assert '1' == json_dump(Int(1))
+
 assert '0.5' == json.dumps(Float(0.5))
+assert '0.5' == json_dump(Float(0.5))
 
 class List(list): pass
 class Tuple(tuple): pass
 class Dict(dict): pass
 
 assert '[1]' == json.dumps(List([1]))
+assert '[1]' == json_dump(List([1]))
+
 assert json.dumps((1, "string", 1.0, True)) == json.dumps(Tuple((1, "string", 1.0, True)))
+assert json_dump((1, "string", 1.0, True)) == json_dump(Tuple((1, "string", 1.0, True)))
+
 assert json.dumps({'a': 'b'}) == json.dumps(Dict({'a': 'b'}))
+assert json_dump({'a': 'b'}) == json_dump(Dict({'a': 'b'}))
 
 # big ints should not crash VM
 # TODO: test for correct output when actual serialization implemented and doesn’t throw