Add tests for SciType validators

Author: vidartf

traittypes/tests/test_validators.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+import pytest
+
+from traitlets import HasTraits, TraitError
+
+from ..traittypes import SciType
+
+
+def test_coercion_validator():
+    # Test with a squeeze coercion
+    def truncate(trait, value):
+        return value[:10]
+
+    class Foo(HasTraits):
+        bar = SciType().valid(truncate)
+
+    foo = Foo(bar=list(range(20)))
+    assert foo.bar == list(range(10))
+    foo.bar = list(range(10, 40))
+    assert foo.bar == list(range(10, 20))
+
+
+def test_validaton_error():
+    # Test with a squeeze coercion
+    def maxlen(trait, value):
+        if len(value) > 10:
+            raise ValueError('Too long sequence!')
+        return value
+
+    class Foo(HasTraits):
+        bar = SciType().valid(maxlen)
+
+    # Check that it works as expected:
+    foo = Foo(bar=list(range(5)))
+    assert foo.bar == list(range(5))
+    # Check that it fails as expected:
+    with pytest.raises(TraitError):  # Should convert ValueError to TraitError
+        foo.bar = list(range(10, 40))
+    assert foo.bar == list(range(5))
+    # Check that it can again be set correctly
+    foo = Foo(bar=list(range(5, 10)))
+    assert foo.bar == list(range(5, 10))