diff --git a/jedi/api/__init__.py b/jedi/api/__init__.py
index a5da3c54..1b62ee23 100644
--- a/jedi/api/__init__.py
+++ b/jedi/api/__init__.py
@@ -378,7 +378,7 @@ class Interpreter(Script):
 
 
 def names(source=None, path=None, encoding='utf-8', all_scopes=False,
-          definitions=True, references=False):
+          definitions=True, references=False, environment=None):
     """
     Returns a list of `Definition` objects, containing name parts.
     This means you can call ``Definition.goto_assignments()`` and get the
@@ -398,7 +398,7 @@ def names(source=None, path=None, encoding='utf-8', all_scopes=False,
         return definitions and is_def or references and not is_def
 
     # Set line/column to a random position, because they don't matter.
-    script = Script(source, line=1, column=0, path=path, encoding=encoding)
+    script = Script(source, line=1, column=0, path=path, encoding=encoding, environment=environment)
     module_context = script._get_module()
     defs = [
         classes.Definition(
diff --git a/test/test_api/test_analysis.py b/test/test_api/test_analysis.py
index cfcd405d..f0b6a449 100644
--- a/test/test_api/test_analysis.py
+++ b/test/test_api/test_analysis.py
@@ -1,10 +1,9 @@
 """
 Test of keywords and ``jedi.keywords``
 """
-from jedi import Script
 
 
-def test_issue436():
+def test_issue436(Script):
     code = "bar = 0\nbar += 'foo' + 4"
     errors = set(repr(e) for e in Script(code)._analysis())
     assert len(errors) == 2
diff --git a/test/test_api/test_api_classes_follow_definition.py b/test/test_api/test_api_classes_follow_definition.py
index ffc0cb64..e8342036 100644
--- a/test/test_api/test_api_classes_follow_definition.py
+++ b/test/test_api/test_api_classes_follow_definition.py
@@ -4,26 +4,26 @@ import jedi
 from ..helpers import cwd_at
 
 
-def test_import_empty():
+def test_import_empty(Script):
     """ github #340, return the full word. """
-    completion = jedi.Script("import ").completions()[0]
+    completion = Script("import ").completions()[0]
     definition = completion.follow_definition()[0]
     assert definition
 
 
-def check_follow_definition_types(source):
+def check_follow_definition_types(Script, source):
     # nested import
-    completions = jedi.Script(source, path='some_path.py').completions()
+    completions = Script(source, path='some_path.py').completions()
     defs = chain.from_iterable(c.follow_definition() for c in completions)
     return [d.type for d in defs]
 
 
-def test_follow_import_incomplete():
+def test_follow_import_incomplete(Script):
     """
     Completion on incomplete imports should always take the full completion
     to do any evaluation.
     """
-    datetime = check_follow_definition_types("import itertool")
+    datetime = check_follow_definition_types(Script, "import itertool")
     assert datetime == ['module']
 
     # empty `from * import` parts
@@ -33,30 +33,30 @@ def test_follow_import_incomplete():
     assert [d.type for d in definitions[0].follow_definition()] == ['class']
 
     # incomplete `from * import` part
-    datetime = check_follow_definition_types("from datetime import datetim")
+    datetime = check_follow_definition_types(Script, "from datetime import datetim")
     assert set(datetime) == set(['class', 'instance'])  # py33: builtin and pure py version
 
     # os.path check
-    ospath = check_follow_definition_types("from os.path import abspat")
+    ospath = check_follow_definition_types(Script, "from os.path import abspat")
     assert ospath == ['function']
 
     # alias
-    alias = check_follow_definition_types("import io as abcd; abcd")
+    alias = check_follow_definition_types(Script, "import io as abcd; abcd")
     assert alias == ['module']
 
 
 @cwd_at('test/completion/import_tree')
-def test_follow_definition_nested_import():
-    types = check_follow_definition_types("import pkg.mod1; pkg")
+def test_follow_definition_nested_import(Script):
+    types = check_follow_definition_types(Script, "import pkg.mod1; pkg")
     assert types == ['module']
 
-    types = check_follow_definition_types("import pkg.mod1; pkg.mod1")
+    types = check_follow_definition_types(Script, "import pkg.mod1; pkg.mod1")
     assert types == ['module']
 
-    types = check_follow_definition_types("import pkg.mod1; pkg.mod1.a")
+    types = check_follow_definition_types(Script, "import pkg.mod1; pkg.mod1.a")
     assert types == ['instance']
 
 
-def test_follow_definition_land_on_import():
-    types = check_follow_definition_types("import datetime; datetim")
+def test_follow_definition_land_on_import(Script):
+    types = check_follow_definition_types(Script, "import datetime; datetim")
     assert types == ['module']
diff --git a/test/test_api/test_call_signatures.py b/test/test_api/test_call_signatures.py
index ffafb4ea..77a58005 100644
--- a/test/test_api/test_call_signatures.py
+++ b/test/test_api/test_call_signatures.py
@@ -2,13 +2,14 @@ from textwrap import dedent
 import inspect
 import warnings
 
+import pytest
+
 from ..helpers import TestCase
-from jedi import Script
 from jedi import cache
-from jedi._compatibility import is_py33, py_version
+from jedi._compatibility import is_py33
 
 
-def assert_signature(source, expected_name, expected_index=0, line=None, column=None):
+def assert_signature(Script, source, expected_name, expected_index=0, line=None, column=None):
     signatures = Script(source, line, column).call_signatures()
 
     assert len(signatures) <= 1
@@ -22,12 +23,17 @@ def assert_signature(source, expected_name, expected_index=0, line=None, column=
         return signatures[0]
 
 
-class TestCallSignatures(TestCase):
-    def _run_simple(self, source, name, index=0, column=None, line=1):
-        assert_signature(source, name, index, line, column)
+def test_valid_call(Script):
+    assert_signature(Script, 'str()', 'str', column=4)
 
-    def test_valid_call(self):
-        assert_signature('str()', 'str', column=4)
+
+class TestCallSignatures(TestCase):
+    @pytest.fixture(autouse=True)
+    def init(self, Script):
+        self.Script = Script
+
+    def _run_simple(self, source, name, index=0, column=None, line=1):
+        assert_signature(self.Script, source, name, index, line, column)
 
     def test_simple(self):
         run = self._run_simple
@@ -89,170 +95,185 @@ class TestCallSignatures(TestCase):
         self._run_simple("for sorted(", 'sorted', 0)
         self._run_simple("for s in sorted(", 'sorted', 0)
 
-    def test_complex(self):
-        s = """
-                def abc(a,b):
-                    pass
 
-                def a(self):
-                    abc(
+def test_call_signatures_empty_parentheses_pre_space(Script):
+    s = dedent("""\
+    def f(a, b):
+        pass
+    f( )""")
+    assert_signature(Script, s, 'f', 0, line=3, column=3)
 
-                if 1:
-                    pass
-            """
-        assert_signature(s, 'abc', 0, line=6, column=24)
-        s = """
-                import re
-                def huhu(it):
-                    re.compile(
-                    return it * 2
-            """
-        assert_signature(s, 'compile', 0, line=4, column=31)
 
-        # jedi-vim #70
-        s = """def foo("""
-        assert Script(s).call_signatures() == []
-
-        # jedi-vim #116
-        s = """import itertools; test = getattr(itertools, 'chain'); test("""
-        assert_signature(s, 'chain', 0)
-
-    def test_call_signature_on_module(self):
-        """github issue #240"""
-        s = 'import datetime; datetime('
-        # just don't throw an exception (if numpy doesn't exist, just ignore it)
-        assert Script(s).call_signatures() == []
-
-    def test_call_signatures_empty_parentheses_pre_space(self):
-        s = dedent("""\
+def test_multiple_signatures(Script):
+    s = dedent("""\
+    if x:
         def f(a, b):
             pass
-        f( )""")
-        assert_signature(s, 'f', 0, line=3, column=3)
-
-    def test_multiple_signatures(self):
-        s = dedent("""\
-        if x:
-            def f(a, b):
-                pass
-        else:
-            def f(a, b):
-                pass
-        f(""")
-        assert len(Script(s).call_signatures()) == 2
-
-    def test_call_signatures_whitespace(self):
-        s = dedent("""\
-        abs( 
-        def x():
+    else:
+        def f(a, b):
             pass
-        """)
-        assert_signature(s, 'abs', 0, line=1, column=5)
+    f(""")
+    assert len(Script(s).call_signatures()) == 2
 
-    def test_decorator_in_class(self):
+
+def test_call_signatures_whitespace(Script):
+    s = dedent("""\
+    abs( 
+    def x():
+        pass
+    """)
+    assert_signature(Script, s, 'abs', 0, line=1, column=5)
+
+
+def test_decorator_in_class(Script):
+    """
+    There's still an implicit param, with a decorator.
+    Github issue #319.
+    """
+    s = dedent("""\
+    def static(func):
+        def wrapped(obj, *args):
+            return f(type(obj), *args)
+        return wrapped
+
+    class C(object):
+        @static
+        def test(cls):
+            return 10
+
+    C().test(""")
+
+    signatures = Script(s).call_signatures()
+    assert len(signatures) == 1
+    x = [p.description for p in signatures[0].params]
+    assert x == ['param *args']
+
+
+def test_additional_brackets(Script):
+    assert_signature(Script, 'str((', 'str', 0)
+
+
+def test_unterminated_strings(Script):
+    assert_signature(Script, 'str(";', 'str', 0)
+
+
+def test_whitespace_before_bracket(Script):
+    assert_signature(Script, 'str (', 'str', 0)
+    assert_signature(Script, 'str (";', 'str', 0)
+    assert_signature(Script, 'str\n(', None)
+
+
+def test_brackets_in_string_literals(Script):
+    assert_signature(Script, 'str (" (', 'str', 0)
+    assert_signature(Script, 'str (" )', 'str', 0)
+
+
+def test_function_definitions_should_break(Script):
+    """
+    Function definitions (and other tokens that cannot exist within call
+    signatures) should break and not be able to return a call signature.
+    """
+    assert_signature(Script, 'str(\ndef x', 'str', 0)
+    assert not Script('str(\ndef x(): pass').call_signatures()
+
+
+def test_flow_call(Script):
+    assert not Script('if (1').call_signatures()
+
+
+def test_chained_calls(Script):
+    source = dedent('''
+    class B():
+      def test2(self, arg):
+        pass
+
+    class A():
+      def test1(self):
+        return B()
+
+    A().test1().test2(''')
+
+    assert_signature(Script, source, 'test2', 0)
+
+
+def test_return(Script):
+    source = dedent('''
+    def foo():
+        return '.'.join()''')
+
+    assert_signature(Script, source, 'join', 0, column=len("    return '.'.join("))
+
+
+def test_call_signature_on_module(Script):
+    """github issue #240"""
+    s = 'import datetime; datetime('
+    # just don't throw an exception (if numpy doesn't exist, just ignore it)
+    assert Script(s).call_signatures() == []
+
+
+def test_complex(Script):
+    s = """
+            def abc(a,b):
+                pass
+
+            def a(self):
+                abc(
+
+            if 1:
+                pass
         """
-        There's still an implicit param, with a decorator.
-        Github issue #319.
+    assert_signature(Script, s, 'abc', 0, line=6, column=20)
+    s = """
+            import re
+            def huhu(it):
+                re.compile(
+                return it * 2
         """
-        s = dedent("""\
-        def static(func):
-            def wrapped(obj, *args):
-                return f(type(obj), *args)
-            return wrapped
+    assert_signature(Script, s, 'compile', 0, line=4, column=27)
 
-        class C(object):
-            @static
-            def test(cls):
-                return 10
+    # jedi-vim #70
+    s = """def foo("""
+    assert Script(s).call_signatures() == []
 
-        C().test(""")
-
-        signatures = Script(s).call_signatures()
-        assert len(signatures) == 1
-        x = [p.description for p in signatures[0].params]
-        assert x == ['param *args']
-
-    def test_additional_brackets(self):
-        assert_signature('str((', 'str', 0)
-
-    def test_unterminated_strings(self):
-        assert_signature('str(";', 'str', 0)
-
-    def test_whitespace_before_bracket(self):
-        assert_signature('str (', 'str', 0)
-        assert_signature('str (";', 'str', 0)
-        assert_signature('str\n(', None)
-
-    def test_brackets_in_string_literals(self):
-        assert_signature('str (" (', 'str', 0)
-        assert_signature('str (" )', 'str', 0)
-
-    def test_function_definitions_should_break(self):
-        """
-        Function definitions (and other tokens that cannot exist within call
-        signatures) should break and not be able to return a call signature.
-        """
-        assert_signature('str(\ndef x', 'str', 0)
-        assert not Script('str(\ndef x(): pass').call_signatures()
-
-    def test_flow_call(self):
-        assert not Script('if (1').call_signatures()
-
-    def test_chained_calls(self):
-        source = dedent('''
-        class B():
-          def test2(self, arg):
-            pass
-
-        class A():
-          def test1(self):
-            return B()
-
-        A().test1().test2(''')
-
-        assert_signature(source, 'test2', 0)
-
-    def test_return(self):
-        source = dedent('''
-        def foo():
-            return '.'.join()''')
-
-        assert_signature(source, 'join', 0, column=len("    return '.'.join("))
+    # jedi-vim #116
+    s = """import itertools; test = getattr(itertools, 'chain'); test("""
+    assert_signature(Script, s, 'chain', 0)
 
 
-class TestParams(TestCase):
-    def params(self, source, line=None, column=None):
-        signatures = Script(source, line, column).call_signatures()
-        assert len(signatures) == 1
-        return signatures[0].params
-
-    def test_param_name(self):
-        if not is_py33:
-            p = self.params('''int(''')
-            # int is defined as: `int(x[, base])`
-            assert p[0].name == 'x'
-            # `int` docstring has been redefined:
-            # http://bugs.python.org/issue14783
-            # TODO have multiple call signatures for int (like in the docstr)
-            #assert p[1].name == 'base'
-
-        p = self.params('''open(something,''')
-        assert p[0].name in ['file', 'name']
-        assert p[1].name == 'mode'
-
-    def test_builtins(self):
-        """
-        The self keyword should be visible even for builtins, if not
-        instantiated.
-        """
-        p = self.params('str.endswith(')
-        assert p[0].name == 'self'
-        assert p[1].name == 'suffix'
-        p = self.params('str().endswith(')
-        assert p[0].name == 'suffix'
+def _params(Script, source, line=None, column=None):
+    signatures = Script(source, line, column).call_signatures()
+    assert len(signatures) == 1
+    return signatures[0].params
 
 
-def test_signature_is_definition():
+def test_param_name(Script):
+    if not is_py33:
+        p = _params(Script, '''int(''')
+        # int is defined as: `int(x[, base])`
+        assert p[0].name == 'x'
+        # `int` docstring has been redefined:
+        # http://bugs.python.org/issue14783
+        # TODO have multiple call signatures for int (like in the docstr)
+        #assert p[1].name == 'base'
+
+    p = _params(Script, '''open(something,''')
+    assert p[0].name in ['file', 'name']
+    assert p[1].name == 'mode'
+
+
+def test_builtins(Script):
+    """
+    The self keyword should be visible even for builtins, if not
+    instantiated.
+    """
+    p = _params(Script, 'str.endswith(')
+    assert p[0].name == 'self'
+    assert p[1].name == 'suffix'
+    p = _params(Script, 'str().endswith(')
+    assert p[0].name == 'suffix'
+
+
+def test_signature_is_definition(Script):
     """
     Through inheritance, a call signature is a sub class of Definition.
     Check if the attributes match.
@@ -279,7 +300,7 @@ def test_signature_is_definition():
                 assert attribute == signature_attribute
 
 
-def test_no_signature():
+def test_no_signature(Script):
     # str doesn't have a __call__ method
     assert Script('str()(').call_signatures() == []
 
@@ -292,7 +313,7 @@ def test_no_signature():
     assert Script('').call_signatures() == []
 
 
-def test_dict_literal_in_incomplete_call():
+def test_dict_literal_in_incomplete_call(Script):
     source = """\
     import json
 
@@ -309,7 +330,7 @@ def test_dict_literal_in_incomplete_call():
     assert script.call_signatures()
 
 
-def test_completion_interference():
+def test_completion_interference(Script):
     """Seems to cause problems, see also #396."""
     cache.parser_cache.pop(None, None)
     assert Script('open(').call_signatures()
@@ -320,12 +341,12 @@ def test_completion_interference():
     assert Script('open(').call_signatures()
 
 
-def test_keyword_argument_index():
+def test_keyword_argument_index(Script, environment):
     def get(source, column=None):
         return Script(source, column=column).call_signatures()[0]
 
     # The signature of sorted changed from 2 to 3.
-    py2_offset = int(py_version < 30)
+    py2_offset = int(environment.version_info.major == 2)
     assert get('sorted([], key=a').index == 1 + py2_offset
     assert get('sorted([], key=').index == 1 + py2_offset
     assert get('sorted([], no_key=a').index is None
@@ -354,7 +375,7 @@ def test_keyword_argument_index():
     assert get(both + 'foo(a, b, c').index == 0
 
 
-def test_bracket_start():
+def test_bracket_start(Script):
     def bracket_start(src):
         signatures = Script(src).call_signatures()
         assert len(signatures) == 1
@@ -363,20 +384,20 @@ def test_bracket_start():
     assert bracket_start('str(') == (1, 3)
 
 
-def test_different_caller():
+def test_different_caller(Script):
     """
     It's possible to not use names, but another function result or an array
     index and then get the call signature of it.
     """
 
-    assert_signature('[str][0](', 'str', 0)
-    assert_signature('[str][0]()', 'str', 0, column=len('[str][0]('))
+    assert_signature(Script, '[str][0](', 'str', 0)
+    assert_signature(Script, '[str][0]()', 'str', 0, column=len('[str][0]('))
 
-    assert_signature('(str)(', 'str', 0)
-    assert_signature('(str)()', 'str', 0, column=len('(str)('))
+    assert_signature(Script, '(str)(', 'str', 0)
+    assert_signature(Script, '(str)()', 'str', 0, column=len('(str)('))
 
 
-def test_in_function():
+def test_in_function(Script):
     code = dedent('''\
     class X():
         @property
@@ -384,7 +405,7 @@ def test_in_function():
     assert not Script(code).call_signatures()
 
 
-def test_lambda_params():
+def test_lambda_params(Script):
     code = dedent('''\
     my_lambda = lambda x: x+1
     my_lambda(1)''')
@@ -394,7 +415,7 @@ def test_lambda_params():
     assert [p.name for p in sig.params] == ['x']
 
 
-def test_class_creation():
+def test_class_creation(Script):
     code = dedent('''\
     class X():
         def __init__(self, foo, bar):
@@ -411,7 +432,7 @@ def test_class_creation():
     assert [p.name for p in sig.params] == ['foo', 'bar']
 
 
-def test_call_magic_method():
+def test_call_magic_method(Script):
     code = dedent('''\
     class X():
         def __call__(self, baz):
diff --git a/test/test_api/test_classes.py b/test/test_api/test_classes.py
index b0f127c4..2089f833 100644
--- a/test/test_api/test_classes.py
+++ b/test/test_api/test_classes.py
@@ -6,19 +6,20 @@ from inspect import cleandoc
 
 import pytest
 
-from jedi import Script, __doc__ as jedi_doc, names
+import jedi
+from jedi import __doc__ as jedi_doc, names
 from ..helpers import cwd_at
 from ..helpers import TestCase
 
 
-def test_is_keyword():
+def test_is_keyword(Script):
     #results = Script('import ', 1, 1, None).goto_definitions()
     #assert len(results) == 1 and results[0].is_keyword is True
     results = Script('str', 1, 1, None).goto_definitions()
     assert len(results) == 1 and results[0].is_keyword is False
 
 
-def test_basedefinition_type():
+def test_basedefinition_type(Script, environment):
     def make_definitions():
         """
         Return a list of definitions for parametrized tests.
@@ -43,7 +44,7 @@ def test_basedefinition_type():
         """)
 
         definitions = []
-        definitions += names(source)
+        definitions += names(source, environment=environment)
 
         source += dedent("""
         variable = sys or C or x or f or g or g() or h""")
@@ -66,7 +67,7 @@ def test_basedefinition_type():
                                    'generator', 'statement', 'import', 'param')
 
 
-def test_basedefinition_type_import():
+def test_basedefinition_type_import(Script):
     def get_types(source, **kwargs):
         return set([t.type for t in Script(source, **kwargs).completions()])
 
@@ -89,7 +90,7 @@ def test_basedefinition_type_import():
     assert get_types('import json.tool', column=9) == set(['module'])
 
 
-def test_function_call_signature_in_doc():
+def test_function_call_signature_in_doc(Script):
     defs = Script("""
     def f(x, y=1, z='a'):
         pass
@@ -98,7 +99,7 @@ def test_function_call_signature_in_doc():
     assert "f(x, y=1, z='a')" in str(doc)
 
 
-def test_class_call_signature():
+def test_class_call_signature(Script):
     defs = Script("""
     class Foo:
         def __init__(self, x, y=1, z='a'):
@@ -108,14 +109,14 @@ def test_class_call_signature():
     assert "Foo(self, x, y=1, z='a')" in str(doc)
 
 
-def test_position_none_if_builtin():
+def test_position_none_if_builtin(Script):
     gotos = Script('import sys; sys.path').goto_assignments()
     assert gotos[0].line is None
     assert gotos[0].column is None
 
 
 @cwd_at('.')
-def test_completion_docstring():
+def test_completion_docstring(Script):
     """
     Jedi should follow imports in certain conditions
     """
@@ -126,7 +127,7 @@ def test_completion_docstring():
     c = Script('import jedi\njed').completions()[0]
     assert c.docstring(fast=False) == cleandoc(jedi_doc)
 
-    docstr('import jedi\njedi.Scr', cleandoc(Script.__doc__))
+    docstr('import jedi\njedi.Scr', cleandoc(jedi.Script.__doc__))
 
     docstr('abcd=3;abcd', '')
     docstr('"hello"\nabcd=3\nabcd', '')
@@ -160,12 +161,12 @@ def test_completion_docstring():
     )
 
 
-def test_completion_params():
+def test_completion_params(Script):
     c = Script('import string; string.capwords').completions()[0]
     assert [p.name for p in c.params] == ['s', 'sep']
 
 
-def test_signature_params():
+def test_signature_params(Script):
     def check(defs):
         params = defs[0].params
         assert len(params) == 1
@@ -182,7 +183,7 @@ def test_signature_params():
     check(Script(s + '\nbar=foo\nbar').goto_assignments())
 
 
-def test_param_endings():
+def test_param_endings(Script):
     """
     Params should be represented without the comma and whitespace they have
     around them.
@@ -192,8 +193,17 @@ def test_param_endings():
 
 
 class TestIsDefinition(TestCase):
+    @pytest.fixture(autouse=True)
+    def init(self, environment):
+        self.environment = environment
+
     def _def(self, source, index=-1):
-        return names(dedent(source), references=True, all_scopes=True)[index]
+        return names(
+            dedent(source),
+            references=True,
+            all_scopes=True,
+            environment=self.environment
+        )[index]
 
     def _bool_is_definitions(self, source):
         ns = names(dedent(source), references=True, all_scopes=True)
@@ -225,8 +235,12 @@ class TestIsDefinition(TestCase):
 
 
 class TestParent(TestCase):
+    @pytest.fixture(autouse=True)
+    def init(self, Script):
+        self.Script = Script
+
     def _parent(self, source, line=None, column=None):
-        def_, = Script(dedent(source), line, column).goto_assignments()
+        def_, = self.Script(dedent(source), line, column).goto_assignments()
         return def_.parent()
 
     def test_parent(self):
@@ -248,20 +262,21 @@ class TestParent(TestCase):
         assert parent.name == ''
         assert parent.type == 'module'
 
-    def test_parent_on_completion(self):
-        parent = Script(dedent('''\
-            class Foo():
-                def bar(): pass
-            Foo().bar''')).completions()[0].parent()
-        assert parent.name == 'Foo'
-        assert parent.type == 'class'
 
-        parent = Script('str.join').completions()[0].parent()
-        assert parent.name == 'str'
-        assert parent.type == 'class'
+def test_parent_on_completion(Script):
+    parent = Script(dedent('''\
+        class Foo():
+            def bar(): pass
+        Foo().bar''')).completions()[0].parent()
+    assert parent.name == 'Foo'
+    assert parent.type == 'class'
+
+    parent = Script('str.join').completions()[0].parent()
+    assert parent.name == 'str'
+    assert parent.type == 'class'
 
 
-def test_type():
+def test_type(Script):
     for c in Script('a = [str()]; a[0].').completions():
         if c.name == '__class__':
             assert c.type == 'class'
@@ -272,7 +287,8 @@ def test_type():
     for c in Script('import os; os.path.').completions():
         assert c.type
 
-def test_type_II():
+
+def test_type_II(Script):
     """
     GitHub Issue #833, `keyword`s are seen as `module`s
     """
@@ -281,100 +297,106 @@ def test_type_II():
             assert c.type == 'keyword'
 
 
-class TestGotoAssignments(TestCase):
-    """
-    This tests the BaseDefinition.goto_assignments function, not the jedi
-    function. They are not really different in functionality, but really
-    different as an implementation.
-    """
-    def test_repetition(self):
-        defs = names('a = 1; a', references=True, definitions=False)
-        # Repeat on the same variable. Shouldn't change once we're on a
-        # definition.
-        for _ in range(3):
-            assert len(defs) == 1
-            ass = defs[0].goto_assignments()
-            assert ass[0].description == 'a = 1'
-
-    def test_named_params(self):
-        src = """\
-                def foo(a=1, bar=2):
-                    pass
-                foo(bar=1)
-              """
-        bar = names(dedent(src), references=True)[-1]
-        param = bar.goto_assignments()[0]
-        assert (param.line, param.column) == (1, 13)
-        assert param.type == 'param'
-
-    def test_class_call(self):
-        src = 'from threading import Thread; Thread(group=1)'
-        n = names(src, references=True)[-1]
-        assert n.name == 'group'
-        param_def = n.goto_assignments()[0]
-        assert param_def.name == 'group'
-        assert param_def.type == 'param'
-
-    def test_parentheses(self):
-        n = names('("").upper', references=True)[-1]
-        assert n.goto_assignments()[0].name == 'upper'
-
-    def test_import(self):
-        nms = names('from json import load', references=True)
-        assert nms[0].name == 'json'
-        assert nms[0].type == 'module'
-        n = nms[0].goto_assignments()[0]
-        assert n.name == 'json'
-        assert n.type == 'module'
-
-        assert nms[1].name == 'load'
-        assert nms[1].type == 'function'
-        n = nms[1].goto_assignments()[0]
-        assert n.name == 'load'
-        assert n.type == 'function'
-
-        nms = names('import os; os.path', references=True)
-        assert nms[0].name == 'os'
-        assert nms[0].type == 'module'
-        n = nms[0].goto_assignments()[0]
-        assert n.name == 'os'
-        assert n.type == 'module'
-
-        n = nms[2].goto_assignments()[0]
-        assert n.name == 'path'
-        assert n.type == 'module'
-
-        nms = names('import os.path', references=True)
-        n = nms[0].goto_assignments()[0]
-        assert n.name == 'os'
-        assert n.type == 'module'
-        n = nms[1].goto_assignments()[0]
-        # This is very special, normally the name doesn't chance, but since
-        # os.path is a sys.modules hack, it does.
-        assert n.name in ('ntpath', 'posixpath', 'os2emxpath')
-        assert n.type == 'module'
-
-    def test_import_alias(self):
-        nms = names('import json as foo', references=True)
-        assert nms[0].name == 'json'
-        assert nms[0].type == 'module'
-        assert nms[0]._name.tree_name.parent.type == 'dotted_as_name'
-        n = nms[0].goto_assignments()[0]
-        assert n.name == 'json'
-        assert n.type == 'module'
-        assert n._name._context.tree_node.type == 'file_input'
-
-        assert nms[1].name == 'foo'
-        assert nms[1].type == 'module'
-        assert nms[1]._name.tree_name.parent.type == 'dotted_as_name'
-        ass = nms[1].goto_assignments()
-        assert len(ass) == 1
-        assert ass[0].name == 'json'
-        assert ass[0].type == 'module'
-        assert ass[0]._name._context.tree_node.type == 'file_input'
+"""
+This tests the BaseDefinition.goto_assignments function, not the jedi
+function. They are not really different in functionality, but really
+different as an implementation.
+"""
 
 
-def test_added_equals_to_params():
+def test_goto_assignment_repetition(environment):
+    defs = names('a = 1; a', references=True, definitions=False, environment=environment)
+    # Repeat on the same variable. Shouldn't change once we're on a
+    # definition.
+    for _ in range(3):
+        assert len(defs) == 1
+        ass = defs[0].goto_assignments()
+        assert ass[0].description == 'a = 1'
+
+
+def test_goto_assignments_named_params(environment):
+    src = """\
+            def foo(a=1, bar=2):
+                pass
+            foo(bar=1)
+          """
+    bar = names(dedent(src), references=True, environment=environment)[-1]
+    param = bar.goto_assignments()[0]
+    assert (param.line, param.column) == (1, 13)
+    assert param.type == 'param'
+
+
+def test_class_call(environment):
+    src = 'from threading import Thread; Thread(group=1)'
+    n = names(src, references=True, environment=environment)[-1]
+    assert n.name == 'group'
+    param_def = n.goto_assignments()[0]
+    assert param_def.name == 'group'
+    assert param_def.type == 'param'
+
+
+def test_parentheses(environment):
+    n = names('("").upper', references=True, environment=environment)[-1]
+    assert n.goto_assignments()[0].name == 'upper'
+
+
+def test_import(environment):
+    nms = names('from json import load', references=True, environment=environment)
+    assert nms[0].name == 'json'
+    assert nms[0].type == 'module'
+    n = nms[0].goto_assignments()[0]
+    assert n.name == 'json'
+    assert n.type == 'module'
+
+    assert nms[1].name == 'load'
+    assert nms[1].type == 'function'
+    n = nms[1].goto_assignments()[0]
+    assert n.name == 'load'
+    assert n.type == 'function'
+
+    nms = names('import os; os.path', references=True, environment=environment)
+    assert nms[0].name == 'os'
+    assert nms[0].type == 'module'
+    n = nms[0].goto_assignments()[0]
+    assert n.name == 'os'
+    assert n.type == 'module'
+
+    n = nms[2].goto_assignments()[0]
+    assert n.name == 'path'
+    assert n.type == 'module'
+
+    nms = names('import os.path', references=True, environment=environment)
+    n = nms[0].goto_assignments()[0]
+    assert n.name == 'os'
+    assert n.type == 'module'
+    n = nms[1].goto_assignments()[0]
+    # This is very special, normally the name doesn't chance, but since
+    # os.path is a sys.modules hack, it does.
+    assert n.name in ('ntpath', 'posixpath', 'os2emxpath')
+    assert n.type == 'module'
+
+
+def test_import_alias(environment):
+    nms = names('import json as foo', references=True, environment=environment)
+    assert nms[0].name == 'json'
+    assert nms[0].type == 'module'
+    assert nms[0]._name.tree_name.parent.type == 'dotted_as_name'
+    n = nms[0].goto_assignments()[0]
+    assert n.name == 'json'
+    assert n.type == 'module'
+    assert n._name._context.tree_node.type == 'file_input'
+
+    assert nms[1].name == 'foo'
+    assert nms[1].type == 'module'
+    assert nms[1]._name.tree_name.parent.type == 'dotted_as_name'
+    ass = nms[1].goto_assignments()
+    assert len(ass) == 1
+    assert ass[0].name == 'json'
+    assert ass[0].type == 'module'
+    assert ass[0]._name._context.tree_node.type == 'file_input'
+
+
+def test_added_equals_to_params(Script):
     def run(rest_source):
         source = dedent("""
         def foo(bar, baz):
diff --git a/test/test_api/test_completion.py b/test/test_api/test_completion.py
index 6cd7e04b..e9bbdb5b 100644
--- a/test/test_api/test_completion.py
+++ b/test/test_api/test_completion.py
@@ -1,15 +1,14 @@
 from textwrap import dedent
-from jedi import Script
 
 
-def test_in_whitespace():
+def test_in_whitespace(Script):
     code = dedent('''
     def x():
         pass''')
     assert len(Script(code, column=2).completions()) > 20
 
 
-def test_empty_init():
+def test_empty_init(Script):
     """This was actually an issue."""
     code = dedent('''\
     class X(object): pass
@@ -17,7 +16,7 @@ def test_empty_init():
     assert Script(code).completions()
 
 
-def test_in_empty_space():
+def test_in_empty_space(Script):
     code = dedent('''\
     class X(object):
         def __init__(self):
@@ -30,7 +29,7 @@ def test_in_empty_space():
     assert def_.name == 'X'
 
 
-def test_indent_context():
+def test_indent_context(Script):
     """
     If an INDENT is the next supposed token, we should still be able to
     complete.
@@ -40,7 +39,7 @@ def test_indent_context():
     assert comp.name == 'isinstance'
 
 
-def test_keyword_context():
+def test_keyword_context(Script):
     def get_names(*args, **kwargs):
         return [d.name for d in Script(*args, **kwargs).completions()]
 
diff --git a/test/test_api/test_defined_names.py b/test/test_api/test_defined_names.py
index b982594b..81b7c5b6 100644
--- a/test/test_api/test_defined_names.py
+++ b/test/test_api/test_defined_names.py
@@ -4,16 +4,22 @@ Tests for `api.defined_names`.
 
 from textwrap import dedent
 
+import pytest
+
 from jedi import names
 from ..helpers import TestCase
 
 
 class TestDefinedNames(TestCase):
+    @pytest.fixture(autouse=True)
+    def init(self, environment):
+        self.environment = environment
+
     def assert_definition_names(self, definitions, names_):
         assert [d.name for d in definitions] == names_
 
     def check_defined_names(self, source, names_):
-        definitions = names(dedent(source))
+        definitions = names(dedent(source), environment=self.environment)
         self.assert_definition_names(definitions, names_)
         return definitions
 
@@ -74,19 +80,19 @@ class TestDefinedNames(TestCase):
         self.assert_definition_names(subsubdefs[0].defined_names(), ['f'])
 
 
-def test_follow_imports():
+def test_follow_imports(environment):
     # github issue #344
-    imp = names('import datetime')[0]
+    imp = names('import datetime', environment=environment)[0]
     assert imp.name == 'datetime'
     datetime_names = [str(d.name) for d in imp.defined_names()]
     assert 'timedelta' in datetime_names
 
 
-def test_names_twice():
+def test_names_twice(environment):
     source = dedent('''
     def lol():
         pass
     ''')
 
-    defs = names(source=source)
+    defs = names(source=source, environment=environment)
     assert defs[0].defined_names() == []
diff --git a/test/test_api/test_full_name.py b/test/test_api/test_full_name.py
index d2ad9d02..eabe6ca2 100644
--- a/test/test_api/test_full_name.py
+++ b/test/test_api/test_full_name.py
@@ -24,8 +24,12 @@ from ..helpers import TestCase
 class MixinTestFullName(object):
     operation = None
 
+    @pytest.fixture(autouse=True)
+    def init(self, Script):
+        self.Script = Script
+
     def check(self, source, desired):
-        script = jedi.Script(textwrap.dedent(source))
+        script = self.Script(textwrap.dedent(source))
         definitions = getattr(script, type(self).operation)()
         for d in definitions:
             self.assertEqual(d.full_name, desired)
@@ -80,25 +84,25 @@ class TestFullDefinedName(TestCase):
         """, ['os', 'os.path', 'os.path.join', 'os.path'])
 
 
-def test_sub_module():
+def test_sub_module(Script):
     """
     ``full_name needs to check sys.path to actually find it's real path module
     path.
     """
-    defs = jedi.Script('from jedi.api import classes; classes').goto_definitions()
+    defs = Script('from jedi.api import classes; classes').goto_definitions()
     assert [d.full_name for d in defs] == ['jedi.api.classes']
-    defs = jedi.Script('import jedi.api; jedi.api').goto_definitions()
+    defs = Script('import jedi.api; jedi.api').goto_definitions()
     assert [d.full_name for d in defs] == ['jedi.api']
 
 
-def test_os_path():
-    d, = jedi.Script('from os.path import join').completions()
+def test_os_path(Script):
+    d, = Script('from os.path import join').completions()
     assert d.full_name == 'os.path.join'
-    d, = jedi.Script('import os.p').completions()
+    d, = Script('import os.p').completions()
     assert d.full_name == 'os.path'
 
 
-def test_os_issues():
+def test_os_issues(Script):
     """Issue #873"""
-    c, = jedi.Script('import os\nos.nt''').completions()
+    c, = Script('import os\nos.nt''').completions()
     assert c.full_name == 'nt'
diff --git a/test/test_api/test_unicode.py b/test/test_api/test_unicode.py
index bcd8ad42..4d3fdf5c 100644
--- a/test/test_api/test_unicode.py
+++ b/test/test_api/test_unicode.py
@@ -2,11 +2,10 @@
 """
 All character set and unicode related tests.
 """
-from jedi import Script
 from jedi._compatibility import u, unicode
 
 
-def test_unicode_script():
+def test_unicode_script(Script):
     """ normally no unicode objects are being used. (<=2.7) """
     s = unicode("import datetime; datetime.timedelta")
     completions = Script(s).completions()
@@ -24,7 +23,7 @@ def test_unicode_script():
     assert type(completions[0].description) is unicode
 
 
-def test_unicode_attribute():
+def test_unicode_attribute(Script):
     """ github jedi-vim issue #94 """
     s1 = u('#-*- coding: utf-8 -*-\nclass Person():\n'
            '    name = "e"\n\nPerson().name.')
@@ -36,7 +35,7 @@ def test_unicode_attribute():
     assert 'strip' in [c.name for c in completions2]
 
 
-def test_multibyte_script():
+def test_multibyte_script(Script):
     """ `jedi.Script` must accept multi-byte string source. """
     try:
         code = u("import datetime; datetime.d")
@@ -48,7 +47,7 @@ def test_multibyte_script():
         assert len(Script(s, 1, len(code)).completions())
 
 
-def test_goto_definition_at_zero():
+def test_goto_definition_at_zero(Script):
     """At zero usually sometimes raises unicode issues."""
     assert Script("a", 1, 1).goto_definitions() == []
     s = Script("str", 1, 1).goto_definitions()
@@ -57,7 +56,7 @@ def test_goto_definition_at_zero():
     assert Script("", 1, 0).goto_definitions() == []
 
 
-def test_complete_at_zero():
+def test_complete_at_zero(Script):
     s = Script("str", 1, 3).completions()
     assert len(s) == 1
     assert list(s)[0].name == 'str'
diff --git a/test/test_api/test_usages.py b/test/test_api/test_usages.py
index 1325e412..94deb0f9 100644
--- a/test/test_api/test_usages.py
+++ b/test/test_api/test_usages.py
@@ -1,6 +1,3 @@
-import jedi
-
-
-def test_import_usage():
-    s = jedi.Script("from .. import foo", line=1, column=18, path="foo.py")
+def test_import_usage(Script):
+    s = Script("from .. import foo", line=1, column=18, path="foo.py")
     assert [usage.line for usage in s.usages()] == [1]