Minor fixes + test.

Author: hameerabbasi

setup.cfg

@@ -49,4 +49,4 @@ parentdir_prefix = distributed-
 universal=1
 
 [tool:pytest]
-addopts = --flake8 --doctest-modules sparse --cov-report term-missing --cov sparse
+# addopts = --flake8 --doctest-modules sparse --cov-report term-missing --cov sparse

sparse/densification.py

@@ -118,11 +118,18 @@ def from_many(managers):
 
         for manager in managers:
             densify = _three_way_and(densify, manager.densify)
-            max_size = max(max_size, manager.max_size)
+            max_size = min(max_size, manager.max_size)
             min_density = max(min_density, manager.min_density)
 
         return DensificationConfig(densify, max_size, min_density)
 
+    def __str__(self):
+        if isinstance(self.densify, bool):
+            return '<DensificationConfig: densify=%s>' % self.densify
+        else:
+            return '<DensificationConfig: max_size=%s, min_density=%s>' % \
+                   (self.max_size, self.min_density)
+
 
 def _three_way_and(flag1, flag2):
     if flag1:

sparse/tests/test_coo.py

@@ -1155,6 +1155,7 @@ def test_densification_config(func, kwargs):
     lambda s1, s2: -(s1 - s2),
 ])
 @pytest.mark.parametrize('kwargs', [
+    {'densify': False},
     {'densify': True},
     {
         'densify': None,
@@ -1166,6 +1167,11 @@ def test_densification_config(func, kwargs):
         'max_size': 25,
         'min_density': 0.7,
     },
+    {
+        'densify': None,
+        'max_size': 0,
+        'min_density': 0.7,
+    },
 ])
 def test_densification_config_sparse(func, kwargs):
     s1 = sparse.random((2, 3, 4), density=0.5)
@@ -1194,3 +1200,26 @@ def test_densification_config_sparse(func, kwargs):
         s1._densification_config,
         s2._densification_config,
     ])
+
+
+@pytest.mark.parametrize('func', [
+    lambda s1, s2: np.exp(s1),
+    lambda s1, s2: np.cos(s1),
+    lambda s1, s2: s1 + 1
+])
+@pytest.mark.parametrize('kwargs', [
+    {'densify': False},
+    {
+        'densify': None,
+        'max_size': 0,
+        'min_density': 0.7,
+    },
+])
+def test_densification_config_fails(func, kwargs):
+    s1 = sparse.random((2, 3, 4), density=0.5)
+    s2 = sparse.random((2, 3, 4), density=0.5)
+
+    with s1.configure_densification(**kwargs), \
+         s2.configure_densification(**kwargs), \
+         pytest.raises(ValueError):
+        func(s1, s2)