Split test_python_types.cpp into builtin_casters, stl and pytypes
diff --git a/tests/test_stl.py b/tests/test_stl.py
new file mode 100644
index 0000000..1c98258
--- /dev/null
+++ b/tests/test_stl.py
@@ -0,0 +1,133 @@
+import pytest
+
+from pybind11_tests import stl as m
+from pybind11_tests import UserType
+
+
+def test_vector(doc):
+    """std::vector <-> list"""
+    l = m.cast_vector()
+    assert l == [1]
+    l.append(2)
+    assert m.load_vector(l)
+    assert m.load_vector(tuple(l))
+
+    assert doc(m.cast_vector) == "cast_vector() -> List[int]"
+    assert doc(m.load_vector) == "load_vector(arg0: List[int]) -> bool"
+
+
+def test_array(doc):
+    """std::array <-> list"""
+    l = m.cast_array()
+    assert l == [1, 2]
+    assert m.load_array(l)
+
+    assert doc(m.cast_array) == "cast_array() -> List[int[2]]"
+    assert doc(m.load_array) == "load_array(arg0: List[int[2]]) -> bool"
+
+
+def test_valarray(doc):
+    """std::valarray <-> list"""
+    l = m.cast_valarray()
+    assert l == [1, 4, 9]
+    assert m.load_valarray(l)
+
+    assert doc(m.cast_valarray) == "cast_valarray() -> List[int]"
+    assert doc(m.load_valarray) == "load_valarray(arg0: List[int]) -> bool"
+
+
+def test_map(doc):
+    """std::map <-> dict"""
+    d = m.cast_map()
+    assert d == {"key": "value"}
+    d["key2"] = "value2"
+    assert m.load_map(d)
+
+    assert doc(m.cast_map) == "cast_map() -> Dict[str, str]"
+    assert doc(m.load_map) == "load_map(arg0: Dict[str, str]) -> bool"
+
+
+def test_set(doc):
+    """std::set <-> set"""
+    s = m.cast_set()
+    assert s == {"key1", "key2"}
+    s.add("key3")
+    assert m.load_set(s)
+
+    assert doc(m.cast_set) == "cast_set() -> Set[str]"
+    assert doc(m.load_set) == "load_set(arg0: Set[str]) -> bool"
+
+
+def test_move_out_container():
+    """Properties use the `reference_internal` policy by default. If the underlying function
+    returns an rvalue, the policy is automatically changed to `move` to avoid referencing
+    a temporary. In case the return value is a container of user-defined types, the policy
+    also needs to be applied to the elements, not just the container."""
+    c = m.MoveOutContainer()
+    moved_out_list = c.move_list
+    assert [x.value for x in moved_out_list] == [0, 1, 2]
+
+
+@pytest.mark.skipif(not hasattr(m, "has_optional"), reason='no <optional>')
+def test_optional():
+    assert m.double_or_zero(None) == 0
+    assert m.double_or_zero(42) == 84
+    pytest.raises(TypeError, m.double_or_zero, 'foo')
+
+    assert m.half_or_none(0) is None
+    assert m.half_or_none(42) == 21
+    pytest.raises(TypeError, m.half_or_none, 'foo')
+
+    assert m.test_nullopt() == 42
+    assert m.test_nullopt(None) == 42
+    assert m.test_nullopt(42) == 42
+    assert m.test_nullopt(43) == 43
+
+    assert m.test_no_assign() == 42
+    assert m.test_no_assign(None) == 42
+    assert m.test_no_assign(m.NoAssign(43)) == 43
+    pytest.raises(TypeError, m.test_no_assign, 43)
+
+    assert m.nodefer_none_optional(None)
+
+
+@pytest.mark.skipif(not hasattr(m, "has_exp_optional"), reason='no <experimental/optional>')
+def test_exp_optional():
+    assert m.double_or_zero_exp(None) == 0
+    assert m.double_or_zero_exp(42) == 84
+    pytest.raises(TypeError, m.double_or_zero_exp, 'foo')
+
+    assert m.half_or_none_exp(0) is None
+    assert m.half_or_none_exp(42) == 21
+    pytest.raises(TypeError, m.half_or_none_exp, 'foo')
+
+    assert m.test_nullopt_exp() == 42
+    assert m.test_nullopt_exp(None) == 42
+    assert m.test_nullopt_exp(42) == 42
+    assert m.test_nullopt_exp(43) == 43
+
+    assert m.test_no_assign_exp() == 42
+    assert m.test_no_assign_exp(None) == 42
+    assert m.test_no_assign_exp(m.NoAssign(43)) == 43
+    pytest.raises(TypeError, m.test_no_assign_exp, 43)
+
+
+@pytest.mark.skipif(not hasattr(m, "load_variant"), reason='no <variant>')
+def test_variant(doc):
+    assert m.load_variant(1) == "int"
+    assert m.load_variant("1") == "std::string"
+    assert m.load_variant(1.0) == "double"
+    assert m.load_variant(None) == "std::nullptr_t"
+
+    assert m.load_variant_2pass(1) == "int"
+    assert m.load_variant_2pass(1.0) == "double"
+
+    assert m.cast_variant() == (5, "Hello")
+
+    assert doc(m.load_variant) == "load_variant(arg0: Union[int, str, float, None]) -> str"
+
+
+def test_vec_of_reference_wrapper():
+    """#171: Can't return reference wrappers (or STL structures containing them)"""
+    assert str(m.return_vec_of_reference_wrapper(UserType(4))) == \
+        "[UserType(1), UserType(2), UserType(3), UserType(4)]"