diff --git a/conftest.py b/conftest.py
index a9e31ad2..e0914dcc 100644
--- a/conftest.py
+++ b/conftest.py
@@ -105,6 +105,11 @@ def Script(environment):
     return partial(jedi.Script, environment=environment)
 
 
+@pytest.fixture(scope='session')
+def names(environment):
+    return partial(jedi.names, environment=environment)
+
+
 @pytest.fixture(scope='session')
 def has_typing(environment):
     if environment.version_info >= (3, 5, 0):
diff --git a/test/test_api/test_defined_names.py b/test/test_api/test_defined_names.py
index dac46ff8..d4e97ea1 100644
--- a/test/test_api/test_defined_names.py
+++ b/test/test_api/test_defined_names.py
@@ -4,28 +4,21 @@ Tests for `api.defined_names`.
 
 from textwrap import dedent
 
-import pytest
-
 from jedi import names
-from ..helpers import TestCase
 
 
 def _assert_definition_names(definitions, names_):
     assert [d.name for d in definitions] == names_
 
 
-class TestDefinedNames(TestCase):
-    @pytest.fixture(autouse=True)
-    def init(self, environment):
-        self.environment = environment
+def _check_defined_names(names, source, names_):
+    definitions = names(dedent(source))
+    _assert_definition_names(definitions, names_)
+    return definitions
 
-    def check_defined_names(self, source, names_):
-        definitions = names(dedent(source), environment=self.environment)
-        _assert_definition_names(definitions, names_)
-        return definitions
 
-    def test_get_definitions_flat(self):
-        self.check_defined_names("""
+def test_get_definitions_flat(names):
+    _check_defined_names(names, """
         import module
         class Class:
             pass
@@ -34,105 +27,109 @@ class TestDefinedNames(TestCase):
         data = None
         """, ['module', 'Class', 'func', 'data'])
 
-    def test_dotted_assignment(self):
-        self.check_defined_names("""
-        x = Class()
-        x.y.z = None
-        """, ['x', 'z'])  # TODO is this behavior what we want?
 
-    def test_multiple_assignment(self):
-        self.check_defined_names("""
-        x = y = None
-        """, ['x', 'y'])
+def test_dotted_assignment(names):
+    _check_defined_names(names, """
+    x = Class()
+    x.y.z = None
+    """, ['x', 'z'])  # TODO is this behavior what we want?
 
-    def test_multiple_imports(self):
-        self.check_defined_names("""
-        from module import a, b
-        from another_module import *
-        """, ['a', 'b'])
 
-    def test_nested_definitions(self):
-        definitions = self.check_defined_names("""
-        class Class:
-            def f():
-                pass
-            def g():
-                pass
-        """, ['Class'])
-        subdefinitions = definitions[0].defined_names()
-        _assert_definition_names(subdefinitions, ['f', 'g'])
-        self.assertEqual([d.full_name for d in subdefinitions],
-                         ['__main__.Class.f', '__main__.Class.g'])
+def test_multiple_assignment(names):
+    _check_defined_names(names, "x = y = None", ['x', 'y'])
 
-    def test_nested_class(self):
-        definitions = self.check_defined_names("""
-        class L1:
-            class L2:
-                class L3:
-                    def f(): pass
+
+def test_multiple_imports(names):
+    _check_defined_names(names, """
+    from module import a, b
+    from another_module import *
+    """, ['a', 'b'])
+
+
+def test_nested_definitions(names):
+    definitions = _check_defined_names(names, """
+    class Class:
+        def f():
+            pass
+        def g():
+            pass
+    """, ['Class'])
+    subdefinitions = definitions[0].defined_names()
+    _assert_definition_names(subdefinitions, ['f', 'g'])
+    assert [d.full_name for d in subdefinitions] == ['__main__.Class.f', '__main__.Class.g']
+
+
+def test_nested_class(names):
+    definitions = _check_defined_names(names, """
+    class L1:
+        class L2:
+            class L3:
                 def f(): pass
             def f(): pass
         def f(): pass
-        """, ['L1', 'f'])
-        subdefs = definitions[0].defined_names()
-        subsubdefs = subdefs[0].defined_names()
-        _assert_definition_names(subdefs, ['L2', 'f'])
-        _assert_definition_names(subsubdefs, ['L3', 'f'])
-        _assert_definition_names(subsubdefs[0].defined_names(), ['f'])
+    def f(): pass
+    """, ['L1', 'f'])
+    subdefs = definitions[0].defined_names()
+    subsubdefs = subdefs[0].defined_names()
+    _assert_definition_names(subdefs, ['L2', 'f'])
+    _assert_definition_names(subsubdefs, ['L3', 'f'])
+    _assert_definition_names(subsubdefs[0].defined_names(), ['f'])
 
-    def test_class_fields_with_all_scopes_false(self):
-        definitions = self.check_defined_names("""
-        from module import f
-        g = f(f)
-        class C:
-            h = g
 
-        def foo(x=a):
-           bar = x
-           return bar
-        """, ['f', 'g', 'C', 'foo'])
-        C_subdefs = definitions[-2].defined_names()
-        foo_subdefs = definitions[-1].defined_names()
-        _assert_definition_names(C_subdefs, ['h'])
-        _assert_definition_names(foo_subdefs, ['x', 'bar'])
+def test_class_fields_with_all_scopes_false(names):
+    definitions = _check_defined_names(names, """
+    from module import f
+    g = f(f)
+    class C:
+        h = g
 
-    def test_async_stmt_with_all_scopes_false(self):
-        definitions = self.check_defined_names("""
-        from module import f
-        import asyncio
+    def foo(x=a):
+       bar = x
+       return bar
+    """, ['f', 'g', 'C', 'foo'])
+    C_subdefs = definitions[-2].defined_names()
+    foo_subdefs = definitions[-1].defined_names()
+    _assert_definition_names(C_subdefs, ['h'])
+    _assert_definition_names(foo_subdefs, ['x', 'bar'])
 
-        g = f(f)
-        class C:
-            h = g
-            def __init__(self):
-                pass
 
-            async def __aenter__(self):
-                pass
+def test_async_stmt_with_all_scopes_false(names):
+    definitions = _check_defined_names(names, """
+    from module import f
+    import asyncio
 
-        def foo(x=a):
-           bar = x
-           return bar
+    g = f(f)
+    class C:
+        h = g
+        def __init__(self):
+            pass
 
-        async def async_foo(duration):
-            async def wait():
-                await asyncio.sleep(100)
-            for i in range(duration//100):
-                await wait()
-            return duration//100*100
+        async def __aenter__(self):
+            pass
 
-        async with C() as cinst:
-            d = cinst
-        """, ['f', 'asyncio', 'g', 'C', 'foo', 'async_foo', 'cinst', 'd'])
-        C_subdefs = definitions[3].defined_names()
-        foo_subdefs = definitions[4].defined_names()
-        async_foo_subdefs = definitions[5].defined_names()
-        cinst_subdefs = definitions[6].defined_names()
-        _assert_definition_names(C_subdefs, ['h', '__init__', '__aenter__'])
-        _assert_definition_names(foo_subdefs, ['x', 'bar'])
-        _assert_definition_names(async_foo_subdefs, ['duration', 'wait', 'i'])
-        # We treat d as a name outside `async with` block
-        _assert_definition_names(cinst_subdefs, [])
+    def foo(x=a):
+       bar = x
+       return bar
+
+    async def async_foo(duration):
+        async def wait():
+            await asyncio.sleep(100)
+        for i in range(duration//100):
+            await wait()
+        return duration//100*100
+
+    async with C() as cinst:
+        d = cinst
+    """, ['f', 'asyncio', 'g', 'C', 'foo', 'async_foo', 'cinst', 'd'])
+    C_subdefs = definitions[3].defined_names()
+    foo_subdefs = definitions[4].defined_names()
+    async_foo_subdefs = definitions[5].defined_names()
+    cinst_subdefs = definitions[6].defined_names()
+    _assert_definition_names(C_subdefs, ['h', '__init__', '__aenter__'])
+    _assert_definition_names(foo_subdefs, ['x', 'bar'])
+    _assert_definition_names(async_foo_subdefs, ['duration', 'wait', 'i'])
+    # We treat d as a name outside `async with` block
+    _assert_definition_names(cinst_subdefs, [])
 
 
 def test_follow_imports(environment):