add min, max length support to iterables

plenum/common/messages/fields.py

@@ -194,14 +194,28 @@ def _specific_validation(self, val):
 class IterableField(FieldBase):
     _base_types = (list, tuple)
 
-    def __init__(self, inner_field_type: FieldValidator, **kwargs):
+    def __init__(self, inner_field_type: FieldValidator, min_length=None,
+                 max_length=None, **kwargs):
         assert inner_field_type
         assert isinstance(inner_field_type, FieldValidator)
+        for m in (min_length, max_length):
+            if m is not None:
+                assert isinstance(m, int)
+                assert m > 0
 
         self.inner_field_type = inner_field_type
+        self.min_length = min_length
+        self.max_length = max_length
         super().__init__(**kwargs)
 
     def _specific_validation(self, val):
+        if self.min_length is not None:
+            if len(val) < self.min_length:
+                return 'length should be at least {}'.format(self.min_length)
+        if self.max_length is not None:
+            if len(val) > self.max_length:
+                return 'length should be at most {}'.format(self.max_length)
+
         for v in val:
             check_er = self.inner_field_type.validate(v)
             if check_er:

plenum/test/helper.py

@@ -828,7 +828,8 @@ def chk():
                 if fails >= acceptable_fails:
                     logger.debug('Too many fails, the last one: {}'.format(repr(ex)))
                 last_ex = ex
-        assert fails <= acceptable_fails, str(last_ex)
+        assert fails <= acceptable_fails, '{} out of {} failed. Last exception:' \
+                                          ' {}'.format(fails, len(funcs), last_ex)
 
     kwargs = {}
     if retry_wait:

plenum/test/input_validation/fields_validation/test_iterable_field.py

@@ -13,3 +13,34 @@ def test_valid_inner_type():
     validator = IterableField(NonNegativeNumberField())
     assert not validator.validate([1, 2, 3])
     assert validator.validate([1, 2, -3])
+
+
+def test_valid_min_max_vals():
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), min_length=0)
+
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), max_length=0)
+
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), min_length=-1)
+
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), max_length=-5)
+
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), min_length=2.5)
+
+    with pytest.raises(Exception):
+        IterableField(NonNegativeNumberField(), max_length=3.5)
+
+
+def test_min_max_checks():
+    validator = IterableField(NonNegativeNumberField(), min_length=3,
+                              max_length=10)
+    assert validator.validate(list(range(2)))
+
+    for i in range(3, 11):
+        assert not validator.validate(list(range(i)))
+
+    assert validator.validate(list(range(12)))