DRY in TestAssertionRewrite

testing/test_assertrewrite.py

@@ -65,20 +65,27 @@ def getmsg(f, extra_ns=None, must_pass=False):
             pytest.fail("function didn't raise at all")
 
 
-def python_version_has_docstring_in_module_node():
+def adjust_body_for_new_docstring_in_module_node(m):
     """Module docstrings in 3.8 are part of Module node.
     This was briefly in 3.7 as well but got reverted in beta 5.
 
+    It's not in the body so we remove it so the following body items have
+    the same indexes on all Python versions:
+
     TODO:
 
     We have a complicated sys.version_info if in here to ease testing on
     various Python 3.7 versions, but we should remove the 3.7 check after
     3.7 is released as stable to make this check more straightforward.
     """
-    return (
+    if (
         sys.version_info < (3, 8)
         and not ((3, 7) <= sys.version_info <= (3, 7, 0, "beta", 4))
-    )
+    ):
+        assert len(m.body) > 1
+        assert isinstance(m.body[0], ast.Expr)
+        assert isinstance(m.body[0].value, ast.Str)
+        del m.body[0]
 
 
 class TestAssertionRewrite(object):
@@ -86,13 +93,7 @@ class TestAssertionRewrite(object):
     def test_place_initial_imports(self):
         s = """'Doc string'\nother = stuff"""
         m = rewrite(s)
-        # Module docstrings in some new Python versions are part of Module node
+        adjust_body_for_new_docstring_in_module_node(m)
-        # It's not in the body so we remove it so the following body items have
-        # the same indexes on all Python versions:
-        if python_version_has_docstring_in_module_node():
-            assert isinstance(m.body[0], ast.Expr)
-            assert isinstance(m.body[0].value, ast.Str)
-            del m.body[0]
         for imp in m.body[0:2]:
             assert isinstance(imp, ast.Import)
             assert imp.lineno == 2
@@ -108,10 +109,7 @@ class TestAssertionRewrite(object):
         assert isinstance(m.body[3], ast.Expr)
         s = """'doc string'\nfrom __future__ import with_statement"""
         m = rewrite(s)
-        if python_version_has_docstring_in_module_node():
+        adjust_body_for_new_docstring_in_module_node(m)
-            assert isinstance(m.body[0], ast.Expr)
-            assert isinstance(m.body[0].value, ast.Str)
-            del m.body[0]
         assert isinstance(m.body[0], ast.ImportFrom)
         for imp in m.body[1:3]:
             assert isinstance(imp, ast.Import)
@@ -119,10 +117,7 @@ class TestAssertionRewrite(object):
             assert imp.col_offset == 0
         s = """'doc string'\nfrom __future__ import with_statement\nother"""
         m = rewrite(s)
-        if python_version_has_docstring_in_module_node():
+        adjust_body_for_new_docstring_in_module_node(m)
-            assert isinstance(m.body[0], ast.Expr)
-            assert isinstance(m.body[0].value, ast.Str)
-            del m.body[0]
         assert isinstance(m.body[0], ast.ImportFrom)
         for imp in m.body[1:3]:
             assert isinstance(imp, ast.Import)
@@ -140,13 +135,8 @@ class TestAssertionRewrite(object):
     def test_dont_rewrite(self):
         s = """'PYTEST_DONT_REWRITE'\nassert 14"""
         m = rewrite(s)
-        if python_version_has_docstring_in_module_node():
+        adjust_body_for_new_docstring_in_module_node(m)
-            assert len(m.body) == 2
+        assert len(m.body) == 1
-            assert isinstance(m.body[0], ast.Expr)
-            assert isinstance(m.body[0].value, ast.Str)
-            del m.body[0]
-        else:
-            assert len(m.body) == 1
         assert m.body[0].msg is None
 
     def test_dont_rewrite_plugin(self, testdir):