refactor: pyupgrade --py36-plus tests/**.py

33 files changed, 171 insertions, 186 deletions

diff --git a/tests/conftest.py b/tests/conftest.py
index 201a6e0e..a2577086 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -111,4 +111,4 @@ def pytest_runtest_call(item):
     """Convert StopEverything into skipped tests."""
     outcome = yield
     if outcome.excinfo and issubclass(outcome.excinfo[0], StopEverything):
-        pytest.skip("Skipping {} for StopEverything: {}".format(item.nodeid, outcome.excinfo[1]))
+        pytest.skip(f"Skipping {item.nodeid} for StopEverything: {outcome.excinfo[1]}")
diff --git a/tests/coveragetest.py b/tests/coveragetest.py
index 1163e349..287b585d 100644
--- a/tests/coveragetest.py
+++ b/tests/coveragetest.py
@@ -61,7 +61,7 @@ class CoverageTest(
     keep_temp_dir = bool(int(os.getenv("COVERAGE_KEEP_TMP", "0")))
 
     def setup_test(self):
-        super(CoverageTest, self).setup_test()
+        super().setup_test()
 
         # Attributes for getting info about what happened.
         self.last_command_status = None
@@ -166,7 +166,7 @@ class CoverageTest(
             if isinstance(lines[0], int):
                 # lines is just a list of numbers, it must match the statements
                 # found in the code.
-                assert statements == lines, "{!r} != {!r}".format(statements, lines)
+                assert statements == lines, f"{statements!r} != {lines!r}"
             else:
                 # lines is a list of possible line number lists, one of them
                 # must match.
@@ -174,18 +174,18 @@ class CoverageTest(
                     if statements == line_list:
                         break
                 else:
-                    assert False, "None of the lines choices matched %r" % (statements,)
+                    assert False, f"None of the lines choices matched {statements!r}"
 
             missing_formatted = analysis.missing_formatted()
             if isinstance(missing, str):
-                msg = "{!r} != {!r}".format(missing_formatted, missing)
+                msg = f"{missing_formatted!r} != {missing!r}"
                 assert missing_formatted == missing, msg
             else:
                 for missing_list in missing:
                     if missing_formatted == missing_list:
                         break
                 else:
-                    assert False, "None of the missing choices matched %r" % (missing_formatted,)
+                    assert False, f"None of the missing choices matched {missing_formatted!r}"
 
         if arcs is not None:
             # print("Possible arcs:")
@@ -206,7 +206,7 @@ class CoverageTest(
             frep = io.StringIO()
             cov.report(mod, file=frep, show_missing=True)
             rep = " ".join(frep.getvalue().split("\n")[2].split()[1:])
-            assert report == rep, "{!r} != {!r}".format(report, rep)
+            assert report == rep, f"{report!r} != {rep!r}"
 
         return cov
 
@@ -232,7 +232,7 @@ class CoverageTest(
             """A fake implementation of Coverage._warn, to capture warnings."""
             # NOTE: we don't implement `once`.
             if slug:
-                msg = "%s (%s)" % (msg, slug)
+                msg = f"{msg} ({slug})"
             saved_warnings.append(msg)
 
         original_warn = cov._warn
@@ -249,17 +249,17 @@ class CoverageTest(
                         if re.search(warning_regex, saved):
                             break
                     else:
-                        msg = "Didn't find warning %r in %r" % (warning_regex, saved_warnings)
+                        msg = f"Didn't find warning {warning_regex!r} in {saved_warnings!r}"
                         assert False, msg
                 for warning_regex in not_warnings:
                     for saved in saved_warnings:
                         if re.search(warning_regex, saved):
-                            msg = "Found warning %r in %r" % (warning_regex, saved_warnings)
+                            msg = f"Found warning {warning_regex!r} in {saved_warnings!r}"
                             assert False, msg
             else:
                 # No warnings expected. Raise if any warnings happened.
                 if saved_warnings:
-                    assert False, "Unexpected warnings: %r" % (saved_warnings,)
+                    assert False, f"Unexpected warnings: {saved_warnings!r}"
         finally:
             cov._warn = original_warn
 
@@ -305,7 +305,7 @@ class CoverageTest(
 
         """
         ret_actual = command_line(args)
-        assert ret_actual == ret, "{!r} != {!r}".format(ret_actual, ret)
+        assert ret_actual == ret, f"{ret_actual!r} != {ret!r}"
 
     # Some distros rename the coverage command, and need a way to indicate
     # their new command name to the tests. This is here for them to override,
@@ -440,11 +440,11 @@ class CoverageTest(
                 for filename in coverage_data.measured_files()}
 
 
-class UsingModulesMixin(object):
+class UsingModulesMixin:
     """A mixin for importing modules from tests/modules and tests/moremodules."""
 
     def setup_test(self):
-        super(UsingModulesMixin, self).setup_test()
+        super().setup_test()
 
         # Parent class saves and restores sys.path, we can just modify it.
         sys.path.append(nice_file(TESTS_DIR, "modules"))
diff --git a/tests/goldtest.py b/tests/goldtest.py
index 16301417..7ea42754 100644
--- a/tests/goldtest.py
+++ b/tests/goldtest.py
@@ -44,7 +44,7 @@ def versioned_directory(d):
         subdir = os.path.join(d, version)
         if os.path.exists(subdir):
             return subdir
-    raise Exception("Directory missing: {}".format(d))                  # pragma: only failure
+    raise Exception(f"Directory missing: {d}")                  # pragma: only failure
 
 
 def compare(
@@ -95,17 +95,17 @@ def compare(
             expected = scrub(expected, scrubs)
             actual = scrub(actual, scrubs)
         if expected != actual:                              # pragma: only failure
-            text_diff.append('%s != %s' % (expected_file, actual_file))
+            text_diff.append(f'{expected_file} != {actual_file}')
             expected = expected.splitlines()
             actual = actual.splitlines()
-            print(":::: diff {!r} and {!r}".format(expected_file, actual_file))
+            print(f":::: diff {expected_file!r} and {actual_file!r}")
             print("\n".join(difflib.Differ().compare(expected, actual)))
-            print(":::: end diff {!r} and {!r}".format(expected_file, actual_file))
+            print(f":::: end diff {expected_file!r} and {actual_file!r}")
     assert not text_diff, "Files differ: %s" % '\n'.join(text_diff)
 
-    assert not expected_only, "Files in %s only: %s" % (expected_dir, expected_only)
+    assert not expected_only, f"Files in {expected_dir} only: {expected_only}"
     if not actual_extra:
-        assert not actual_only, "Files in %s only: %s" % (actual_dir, actual_only)
+        assert not actual_only, f"Files in {actual_dir} only: {actual_only}"
 
 
 def canonicalize_xml(xtext):
@@ -124,10 +124,10 @@ def contains(filename, *strlist):
     missing in `filename`.
 
     """
-    with open(filename, "r") as fobj:
+    with open(filename) as fobj:
         text = fobj.read()
     for s in strlist:
-        assert s in text, "Missing content in %s: %r" % (filename, s)
+        assert s in text, f"Missing content in {filename}: {s!r}"
 
 
 def contains_any(filename, *strlist):
@@ -137,7 +137,7 @@ def contains_any(filename, *strlist):
     `filename`.
 
     """
-    with open(filename, "r") as fobj:
+    with open(filename) as fobj:
         text = fobj.read()
     for s in strlist:
         if s in text:
@@ -155,10 +155,10 @@ def doesnt_contain(filename, *strlist):
     `filename`.
 
     """
-    with open(filename, "r") as fobj:
+    with open(filename) as fobj:
         text = fobj.read()
     for s in strlist:
-        assert s not in text, "Forbidden content in %s: %r" % (filename, s)
+        assert s not in text, f"Forbidden content in {filename}: {s!r}"
 
 
 # Helpers
diff --git a/tests/helpers.py b/tests/helpers.py
index 93583b8b..21459cd4 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -12,7 +12,7 @@ import re
 import subprocess
 import textwrap
 
-import mock
+from unittest import mock
 
 from coverage.misc import output_encoding
 
@@ -90,7 +90,7 @@ def nice_file(*fparts):
     return os.path.normcase(os.path.abspath(os.path.realpath(fname)))
 
 
-class CheckUniqueFilenames(object):
+class CheckUniqueFilenames:
     """Asserts the uniqueness of file names passed to a function."""
     def __init__(self, wrapped):
         self.filenames = set()
@@ -115,7 +115,7 @@ class CheckUniqueFilenames(object):
     def wrapper(self, filename, *args, **kwargs):
         """The replacement method.  Check that we don't have dupes."""
         assert filename not in self.filenames, (
-            "File name %r passed to %r twice" % (filename, self.wrapped)
+            f"File name {filename!r} passed to {self.wrapped!r} twice"
             )
         self.filenames.add(filename)
         ret = self.wrapped(filename, *args, **kwargs)
@@ -154,10 +154,8 @@ def remove_files(*patterns):
 
 # Map chars to numbers for arcz_to_arcs
 _arcz_map = {'.': -1}
-_arcz_map.update(dict((c, ord(c) - ord('0')) for c in '123456789'))
-_arcz_map.update(dict(
-    (c, 10 + ord(c) - ord('A')) for c in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
-))
+_arcz_map.update({c: ord(c) - ord('0') for c in '123456789'})
+_arcz_map.update({c: 10 + ord(c) - ord('A') for c in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'})
 
 def arcz_to_arcs(arcz):
     """Convert a compact textual representation of arcs to a list of pairs.
diff --git a/tests/mixins.py b/tests/mixins.py
index 44b16f6c..dd9b4e3e 100644
--- a/tests/mixins.py
+++ b/tests/mixins.py
@@ -18,7 +18,7 @@ import pytest
 from tests.helpers import change_dir, make_file, remove_files
 
 
-class PytestBase(object):
+class PytestBase:
     """A base class to connect to pytest in a test class hierarchy."""
 
     @pytest.fixture(autouse=True)
@@ -49,7 +49,7 @@ class PytestBase(object):
         self._monkeypatch.delenv(name, raising=False)
 
 
-class TempDirMixin(object):
+class TempDirMixin:
     """Provides temp dir and data file helpers for tests."""
 
     # Our own setting: most of these tests run in their own temp directory.
diff --git a/tests/modules/pkg1/__init__.py b/tests/modules/pkg1/__init__.py
index 3390a854..dbef951c 100644
--- a/tests/modules/pkg1/__init__.py
+++ b/tests/modules/pkg1/__init__.py
@@ -1,2 +1,2 @@
 # A simple package for testing with.
-print("pkg1.__init__: %s" % (__name__,))
+print(f"pkg1.__init__: {__name__}")
diff --git a/tests/osinfo.py b/tests/osinfo.py
index f9562deb..ec34c709 100644
--- a/tests/osinfo.py
+++ b/tests/osinfo.py
@@ -50,7 +50,7 @@ elif env.LINUX:
             # Get pseudo file /proc/<pid>/status
             with open('/proc/%d/status' % os.getpid()) as t:
                 v = t.read()
-        except IOError:             # pragma: cant happen
+        except OSError:             # pragma: cant happen
             return 0    # non-Linux?
         # Get VmKey line e.g. 'VmRSS:  9999  kB\n ...'
         i = v.index(key)
diff --git a/tests/test_annotate.py b/tests/test_annotate.py
index 051a31ee..de6edcd0 100644
--- a/tests/test_annotate.py
+++ b/tests/test_annotate.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
diff --git a/tests/test_api.py b/tests/test_api.py
index 57154d64..05554ae4 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -629,7 +629,7 @@ class ApiTest(CoverageTest):
 
         # Labeled data is collected
         data = cov.get_data()
-        assert [u'', u'multiply_six', u'multiply_zero'] == sorted(data.measured_contexts())
+        assert ['', 'multiply_six', 'multiply_zero'] == sorted(data.measured_contexts())
 
         filenames = self.get_measured_filenames(data)
         suite_filename = filenames['testsuite.py']
@@ -667,7 +667,7 @@ class ApiTest(CoverageTest):
 
         # Labeled data is collected
         data = cov.get_data()
-        expected = [u'mysuite', u'mysuite|multiply_six', u'mysuite|multiply_zero']
+        expected = ['mysuite', 'mysuite|multiply_six', 'mysuite|multiply_zero']
         assert expected == sorted(data.measured_contexts())
 
         filenames = self.get_measured_filenames(data)
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index adbbc619..ed5090f5 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -8,7 +8,7 @@ import pprint
 import sys
 import textwrap
 
-import mock
+from unittest import mock
 import pytest
 
 import coverage
@@ -58,7 +58,7 @@ class BaseCmdLineTest(CoverageTest):
         concurrency=None, check_preimported=True, context=None,
     )
 
-    DEFAULT_KWARGS = dict((name, kw) for name, _, kw in _defaults.mock_calls)
+    DEFAULT_KWARGS = {name: kw for name, _, kw in _defaults.mock_calls}
 
     def model_object(self):
         """Return a Mock suitable for use in CoverageScript."""
@@ -113,7 +113,7 @@ class BaseCmdLineTest(CoverageTest):
     def cmd_executes(self, args, code, ret=OK, options=None):
         """Assert that the `args` end up executing the sequence in `code`."""
         called, status = self.mock_command_line(args, options=options)
-        assert status == ret, "Wrong status: got %r, wanted %r" % (status, ret)
+        assert status == ret, f"Wrong status: got {status!r}, wanted {ret!r}"
 
         # Remove all indentation, and execute with mock globals
         code = textwrap.dedent(code)
@@ -157,7 +157,7 @@ class BaseCmdLineTest(CoverageTest):
 
         """
         mk, status = self.mock_command_line(args)
-        assert status == ret, "Wrong status: got %s, wanted %s" % (status, ret)
+        assert status == ret, f"Wrong status: got {status}, wanted {ret}"
         if help_msg:
             assert mk.mock_calls[-1] == ('show_help', (help_msg,), {})
         else:
@@ -846,7 +846,7 @@ class CmdLineStdoutTest(BaseCmdLineTest):
         self.command_line("help")
         lines = self.stdout().splitlines()
         assert len(lines) > 10
-        assert lines[-1] == "Full documentation is at {}".format(__url__)
+        assert lines[-1] == f"Full documentation is at {__url__}"
 
     def test_cmd_help(self):
         self.command_line("help run")
@@ -855,14 +855,14 @@ class CmdLineStdoutTest(BaseCmdLineTest):
         assert "<pyfile>" in lines[0]
         assert "--timid" in out
         assert len(lines) > 20
-        assert lines[-1] == "Full documentation is at {}".format(__url__)
+        assert lines[-1] == f"Full documentation is at {__url__}"
 
     def test_unknown_topic(self):
         # Should probably be an ERR return, but meh.
         self.command_line("help foobar")
         lines = self.stdout().splitlines()
         assert lines[0] == "Don't know topic 'foobar'"
-        assert lines[-1] == "Full documentation is at {}".format(__url__)
+        assert lines[-1] == f"Full documentation is at {__url__}"
 
     def test_error(self):
         self.command_line("fooey kablooey", ret=ERR)
@@ -879,7 +879,7 @@ class CmdMainTest(CoverageTest):
 
     run_in_temp_dir = False
 
-    class CoverageScriptStub(object):
+    class CoverageScriptStub:
         """A stub for coverage.cmdline.CoverageScript, used by CmdMainTest."""
 
         def command_line(self, argv):
@@ -896,11 +896,11 @@ class CmdMainTest(CoverageTest):
             elif argv[0] == 'exit':
                 sys.exit(23)
             else:
-                raise AssertionError("Bad CoverageScriptStub: %r" % (argv,))
+                raise AssertionError(f"Bad CoverageScriptStub: {argv!r}")
             return 0
 
     def setup_test(self):
-        super(CmdMainTest, self).setup_test()
+        super().setup_test()
         old_CoverageScript = coverage.cmdline.CoverageScript
         coverage.cmdline.CoverageScript = self.CoverageScriptStub
         self.addCleanup(setattr, coverage.cmdline, 'CoverageScript', old_CoverageScript)
@@ -929,7 +929,7 @@ class CmdMainTest(CoverageTest):
         assert ret == 23
 
 
-class CoverageReportingFake(object):
+class CoverageReportingFake:
     """A fake Coverage.coverage test double."""
     # pylint: disable=missing-function-docstring
     def __init__(self, report_result, html_result, xml_result, json_report):
diff --git a/tests/test_concurrency.py b/tests/test_concurrency.py
index 9cc1f3b6..a5aed4f1 100644
--- a/tests/test_concurrency.py
+++ b/tests/test_concurrency.py
@@ -240,7 +240,7 @@ class ConcurrencyTest(CoverageTest):
             # If the test fails, it's helpful to see this info:
             fname = abs_file("try_it.py")
             linenos = data.lines(fname)
-            print("{}: {}".format(len(linenos), linenos))
+            print(f"{len(linenos)}: {linenos}")
             print_simple_annotation(code, linenos)
 
             lines = line_count(code)
@@ -408,7 +408,7 @@ class MultiprocessingTest(CoverageTest):
         upto = 30
         code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
         total = sum(x*x if x%2 else x*x*x for x in range(upto))
-        expected_out = "{nprocs} pids, total = {total}".format(nprocs=nprocs, total=total)
+        expected_out = f"{nprocs} pids, total = {total}"
         self.try_multiprocessing_code(code, expected_out, threading, nprocs)
 
     def test_multiprocessing_append(self):
@@ -416,7 +416,7 @@ class MultiprocessingTest(CoverageTest):
         upto = 30
         code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
         total = sum(x*x if x%2 else x*x*x for x in range(upto))
-        expected_out = "{nprocs} pids, total = {total}".format(nprocs=nprocs, total=total)
+        expected_out = f"{nprocs} pids, total = {total}"
         self.try_multiprocessing_code(code, expected_out, threading, nprocs, args="--append")
 
     def test_multiprocessing_and_gevent(self):
@@ -426,7 +426,7 @@ class MultiprocessingTest(CoverageTest):
             SUM_RANGE_WORK + EVENTLET + SUM_RANGE_Q + MULTI_CODE
         ).format(NPROCS=nprocs, UPTO=upto)
         total = sum(sum(range((x + 1) * 100)) for x in range(upto))
-        expected_out = "{nprocs} pids, total = {total}".format(nprocs=nprocs, total=total)
+        expected_out = f"{nprocs} pids, total = {total}"
         self.try_multiprocessing_code(
             code, expected_out, eventlet, nprocs, concurrency="multiprocessing,eventlet"
         )
@@ -450,7 +450,7 @@ class MultiprocessingTest(CoverageTest):
             if start_method and start_method not in multiprocessing.get_all_start_methods():
                 continue
 
-            out = self.run_command("coverage run --rcfile=multi.rc multi.py %s" % (start_method,))
+            out = self.run_command(f"coverage run --rcfile=multi.rc multi.py {start_method}")
             assert out.rstrip() == expected_out
 
             out = self.run_command("coverage combine")
@@ -465,7 +465,7 @@ class MultiprocessingTest(CoverageTest):
         upto = 30
         code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
         total = sum(x*x if x%2 else x*x*x for x in range(upto))
-        expected_out = "{nprocs} pids, total = {total}".format(nprocs=nprocs, total=total)
+        expected_out = f"{nprocs} pids, total = {total}"
         self.try_multiprocessing_code_with_branching(code, expected_out)
 
     def test_multiprocessing_bootstrap_error_handling(self):
@@ -541,7 +541,7 @@ def test_thread_safe_save_data(tmpdir):
 
     # Create some Python modules and put them in the path
     modules_dir = tmpdir.mkdir('test_modules')
-    module_names = ["m{:03d}".format(i) for i in range(1000)]
+    module_names = [f"m{i:03d}" for i in range(1000)]
     for module_name in module_names:
         modules_dir.join(module_name + ".py").write("def f(): pass\n")
 
diff --git a/tests/test_config.py b/tests/test_config.py
index 3330290f..83d756a5 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -6,7 +5,7 @@
 
 from collections import OrderedDict
 
-import mock
+from unittest import mock
 import pytest
 
 import coverage
@@ -83,13 +82,13 @@ class ConfigTest(CoverageTest):
         cov = coverage.Coverage(config_file="pyproject.toml")
         assert cov.config.timid
         assert not cov.config.branch
-        assert cov.config.concurrency == [u"a", u"b"]
-        assert cov.config.data_file == u".hello_kitty.data"
-        assert cov.config.plugins == [u"plugins.a_plugin"]
+        assert cov.config.concurrency == ["a", "b"]
+        assert cov.config.data_file == ".hello_kitty.data"
+        assert cov.config.plugins == ["plugins.a_plugin"]
         assert cov.config.precision == 3
-        assert cov.config.html_title == u"tabblo & «ταБЬℓσ»"
+        assert cov.config.html_title == "tabblo & «ταБЬℓσ»"
         assert round(abs(cov.config.fail_under-90.5), 7) == 0
-        assert cov.config.get_plugin_options("plugins.a_plugin") == {u"hello": u"world"}
+        assert cov.config.get_plugin_options("plugins.a_plugin") == {"hello": "world"}
 
         # Test that our class doesn't reject integers when loading floats
         self.make_file("pyproject.toml", """\
diff --git a/tests/test_context.py b/tests/test_context.py
index 688d5cce..b20ecdef 100644
--- a/tests/test_context.py
+++ b/tests/test_context.py
@@ -205,7 +205,7 @@ def get_qualname():
 
 # pylint: disable=missing-class-docstring, missing-function-docstring, unused-argument
 
-class Parent(object):
+class Parent:
     def meth(self):
         return get_qualname()
 
@@ -216,7 +216,7 @@ class Parent(object):
 class Child(Parent):
     pass
 
-class SomethingElse(object):
+class SomethingElse:
     pass
 
 class MultiChild(SomethingElse, Child):
@@ -273,5 +273,5 @@ class QualnameTest(CoverageTest):
 
     def test_bug_829(self):
         # A class with a name like a function shouldn't confuse qualname_from_frame.
-        class test_something(object):               # pylint: disable=unused-variable
+        class test_something:               # pylint: disable=unused-variable
             assert get_qualname() is None
diff --git a/tests/test_coverage.py b/tests/test_coverage.py
index 559c42a6..3ddc6e86 100644
--- a/tests/test_coverage.py
+++ b/tests/test_coverage.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
diff --git a/tests/test_data.py b/tests/test_data.py
index 30e6df60..867891d4 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -10,7 +10,7 @@ import re
 import sqlite3
 import threading
 
-import mock
+from unittest import mock
 import pytest
 
 from coverage.data import CoverageData, combine_parallel_data
diff --git a/tests/test_execfile.py b/tests/test_execfile.py
index ec8cd180..7c63ac15 100644
--- a/tests/test_execfile.py
+++ b/tests/test_execfile.py
@@ -86,7 +86,7 @@ class RunFileTest(CoverageTest):
 
     def test_no_such_file(self):
         path = python_reported_file('xyzzy.py')
-        msg = re.escape("No file to run: '{}'".format(path))
+        msg = re.escape(f"No file to run: '{path}'")
         with pytest.raises(NoSource, match=msg):
             run_python_file(["xyzzy.py"])
 
@@ -160,7 +160,7 @@ class RunPycFileTest(CoverageTest):
 
     def test_no_such_pyc_file(self):
         path = python_reported_file('xyzzy.pyc')
-        msg = re.escape("No file to run: '{}'".format(path))
+        msg = re.escape(f"No file to run: '{path}'")
         with pytest.raises(NoCode, match=msg):
             run_python_file(["xyzzy.pyc"])
 
@@ -173,7 +173,7 @@ class RunPycFileTest(CoverageTest):
 
         path = python_reported_file('binary')
         msg = (
-            re.escape("Couldn't run '{}' as Python code: ".format(path)) +
+            re.escape(f"Couldn't run '{path}' as Python code: ") +
             r"(TypeError|ValueError): "
             r"("
             r"compile\(\) expected string without null bytes"    # for py2
diff --git a/tests/test_filereporter.py b/tests/test_filereporter.py
index 1e8513f8..e2c71fa2 100644
--- a/tests/test_filereporter.py
+++ b/tests/test_filereporter.py
@@ -103,5 +103,5 @@ class FileReporterTest(UsingModulesMixin, CoverageTest):
 
         z1 = PythonFileReporter(zip1)
         z1z1 = PythonFileReporter(zip1.zip1)
-        assert z1.source() == u""
-        assert u"# My zip file!" in z1z1.source().splitlines()
+        assert z1.source() == ""
+        assert "# My zip file!" in z1z1.source().splitlines()
diff --git a/tests/test_files.py b/tests/test_files.py
index ed6fef26..cfe37460 100644
--- a/tests/test_files.py
+++ b/tests/test_files.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -30,7 +29,7 @@ class FilesTest(CoverageTest):
     def test_simple(self):
         self.make_file("hello.py")
         files.set_relative_directory()
-        assert files.relative_filename(u"hello.py") == u"hello.py"
+        assert files.relative_filename("hello.py") == "hello.py"
         a = self.abs_path("hello.py")
         assert a != "hello.py"
         assert files.relative_filename(a) == "hello.py"
@@ -70,18 +69,18 @@ class FilesTest(CoverageTest):
 
 
 @pytest.mark.parametrize("original, flat", [
-    (u"a/b/c.py", u"a_b_c_py"),
-    (u"c:\\foo\\bar.html", u"_foo_bar_html"),
-    (u"Montréal/☺/conf.py", u"Montréal_☺_conf_py"),
+    ("a/b/c.py", "a_b_c_py"),
+    (r"c:\foo\bar.html", "_foo_bar_html"),
+    ("Montréal/☺/conf.py", "Montréal_☺_conf_py"),
     ( # original:
-        u"c:\\lorem\\ipsum\\quia\\dolor\\sit\\amet\\consectetur\\adipisci\\velit\\sed\\quia\\non"
-        u"\\numquam\\eius\\modi\\tempora\\incidunt\\ut\\labore\\et\\dolore\\magnam\\aliquam"
-        u"\\quaerat\\voluptatem\\ut\\enim\\ad\\minima\\veniam\\quis\\nostrum\\exercitationem"
-        u"\\ullam\\corporis\\suscipit\\laboriosam\\Montréal\\☺\\my_program.py",
+        r"c:\lorem\ipsum\quia\dolor\sit\amet\consectetur\adipisci\velit\sed\quia\non"
+        r"\numquam\eius\modi\tempora\incidunt\ut\labore\et\dolore\magnam\aliquam"
+        r"\quaerat\voluptatem\ut\enim\ad\minima\veniam\quis\nostrum\exercitationem"
+        r"\ullam\corporis\suscipit\laboriosam\Montréal\☺\my_program.py",
         # flat:
-        u"re_et_dolore_magnam_aliquam_quaerat_voluptatem_ut_enim_ad_minima_veniam_quis_"
-        u"nostrum_exercitationem_ullam_corporis_suscipit_laboriosam_Montréal_☺_my_program_py_"
-        u"97eaca41b860faaa1a21349b1f3009bb061cf0a8"
+        "re_et_dolore_magnam_aliquam_quaerat_voluptatem_ut_enim_ad_minima_veniam_quis_"
+        "nostrum_exercitationem_ullam_corporis_suscipit_laboriosam_Montréal_☺_my_program_py_"
+        "97eaca41b860faaa1a21349b1f3009bb061cf0a8"
      ),
 ])
 def test_flat_rootname(original, flat):
@@ -141,13 +140,13 @@ class MatcherTest(CoverageTest):
     """Tests of file matchers."""
 
     def setup_test(self):
-        super(MatcherTest, self).setup_test()
+        super().setup_test()
         files.set_relative_directory()
 
     def assertMatches(self, matcher, filepath, matches):
         """The `matcher` should agree with `matches` about `filepath`."""
         canonical = files.canonical_filename(filepath)
-        msg = "File %s should have matched as %s" % (filepath, matches)
+        msg = f"File {filepath} should have matched as {matches}"
         assert matches == matcher.match(canonical), msg
 
     def test_tree_matcher(self):
diff --git a/tests/test_html.py b/tests/test_html.py
index c561a5d2..3b3250e4 100644
--- a/tests/test_html.py
+++ b/tests/test_html.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -12,7 +11,7 @@ import os.path
 import re
 import sys
 
-import mock
+from unittest import mock
 import pytest
 
 import coverage
@@ -93,11 +92,11 @@ class HtmlTestHelpers(CoverageTest):
         self.assert_recent_datetime(
             timestamp,
             seconds=120,
-            msg="Timestamp is wrong: {}".format(timestamp),
+            msg=f"Timestamp is wrong: {timestamp}",
         )
 
 
-class FileWriteTracker(object):
+class FileWriteTracker:
     """A fake object to track how `open` is used to write files."""
     def __init__(self, written):
         self.written = written
@@ -113,7 +112,7 @@ class HtmlDeltaTest(HtmlTestHelpers, CoverageTest):
     """Tests of the HTML delta speed-ups."""
 
     def setup_test(self):
-        super(HtmlDeltaTest, self).setup_test()
+        super().setup_test()
 
         # At least one of our tests monkey-patches the version of coverage.py,
         # so grab it here to restore it later.
@@ -135,7 +134,7 @@ class HtmlDeltaTest(HtmlTestHelpers, CoverageTest):
         self.files_written = set()
         mock_open = FileWriteTracker(self.files_written).open
         with mock.patch("coverage.html.open", mock_open):
-            return super(HtmlDeltaTest, self).run_coverage(covargs=covargs, htmlargs=htmlargs)
+            return super().run_coverage(covargs=covargs, htmlargs=htmlargs)
 
     def assert_htmlcov_files_exist(self):
         """Assert that all the expected htmlcov files exist."""
@@ -555,7 +554,7 @@ class HtmlStaticFileTest(CoverageTest):
     """Tests of the static file copying for the HTML report."""
 
     def setup_test(self):
-        super(HtmlStaticFileTest, self).setup_test()
+        super().setup_test()
         original_path = list(coverage.html.STATIC_PATH)
         self.addCleanup(setattr, coverage.html, 'STATIC_PATH', original_path)
 
@@ -1039,7 +1038,7 @@ assert len(math) == 18
         doesnt_contain("out/tabbed_py.html", "\t")
 
     def test_unicode(self):
-        surrogate = u"\U000e0100"
+        surrogate = "\U000e0100"
 
         self.make_file("unicode.py", """\
             # -*- coding: utf-8 -*-
diff --git a/tests/test_json.py b/tests/test_json.py
index 47955742..b750a666 100644
--- a/tests/test_json.py
+++ b/tests/test_json.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
diff --git a/tests/test_misc.py b/tests/test_misc.py
index dad542ac..760d8efe 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -36,9 +36,9 @@ class HasherTest(CoverageTest):
 
     def test_unicode_hashing(self):
         h1 = Hasher()
-        h1.update(u"Hello, world! \N{SNOWMAN}")
+        h1.update("Hello, world! \N{SNOWMAN}")
         h2 = Hasher()
-        h2.update(u"Goodbye!")
+        h2.update("Goodbye!")
         assert h1.hexdigest() != h2.hexdigest()
 
     def test_dict_hashing(self):
@@ -90,14 +90,14 @@ class ContractTest(CoverageTest):
         assert need_bytes(b"Hey") == b"Hey"
         assert need_bytes() is None
         with pytest.raises(Exception):
-            need_bytes(u"Oops")
+            need_bytes("Oops")
 
     def test_unicode(self):
         @contract(text='unicode|None')
         def need_unicode(text=None):
             return text
 
-        assert need_unicode(u"Hey") == u"Hey"
+        assert need_unicode("Hey") == "Hey"
         assert need_unicode() is None
         with pytest.raises(Exception):
             need_unicode(b"Oops")
diff --git a/tests/test_mixins.py b/tests/test_mixins.py
index aab1242a..1483b1a2 100644
--- a/tests/test_mixins.py
+++ b/tests/test_mixins.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -65,7 +64,7 @@ class SysPathModulessMixinTest(TempDirMixin, SysPathModulesMixin):
 
     @pytest.mark.parametrize("val", [17, 42])
     def test_module_independence(self, val):
-        self.make_file("xyzzy.py", "A = {}".format(val))
+        self.make_file("xyzzy.py", f"A = {val}")
         import xyzzy            # pylint: disable=import-error
         assert xyzzy.A == val
 
diff --git a/tests/test_numbits.py b/tests/test_numbits.py
index 98399086..3f69b4de 100644
--- a/tests/test_numbits.py
+++ b/tests/test_numbits.py
@@ -99,7 +99,7 @@ class NumbitsSqliteFunctionTest(CoverageTest):
     run_in_temp_dir = False
 
     def setup_test(self):
-        super(NumbitsSqliteFunctionTest, self).setup_test()
+        super().setup_test()
         conn = sqlite3.connect(":memory:")
         register_sqlite_functions(conn)
         self.cursor = conn.cursor()
diff --git a/tests/test_oddball.py b/tests/test_oddball.py
index 2e438396..d6a14f9f 100644
--- a/tests/test_oddball.py
+++ b/tests/test_oddball.py
@@ -271,7 +271,7 @@ class PyexpatTest(CoverageTest):
         # Make sure pyexpat isn't recorded as a source file.
         # https://github.com/nedbat/coveragepy/issues/419
         files = cov.get_data().measured_files()
-        msg = "Pyexpat.c is in the measured files!: %r:" % (files,)
+        msg = f"Pyexpat.c is in the measured files!: {files!r}:"
         assert not any(f.endswith("pyexpat.c") for f in files), msg
 
 
@@ -573,8 +573,7 @@ class MockingProtectionTest(CoverageTest):
         # StopIteration error.
         self.make_file("bug416.py", """\
             import os.path
-
-            import mock
+            from unittest import mock
 
             @mock.patch('os.path.exists')
             def test_path_exists(mock_exists):
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 64839572..4a12c59c 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -236,7 +236,7 @@ class ParserMissingArcDescriptionTest(CoverageTest):
 
     def test_missing_arc_description(self):
         # This code is never run, so the actual values don't matter.
-        parser = self.parse_text(u"""\
+        parser = self.parse_text("""\
             if x:
                 print(2)
             print(3)
@@ -271,7 +271,7 @@ class ParserMissingArcDescriptionTest(CoverageTest):
         assert expected == parser.missing_arc_description(11, 13)
 
     def test_missing_arc_descriptions_for_small_callables(self):
-        parser = self.parse_text(u"""\
+        parser = self.parse_text("""\
             callables = [
                 lambda: 2,
                 (x for x in range(3)),
@@ -290,7 +290,7 @@ class ParserMissingArcDescriptionTest(CoverageTest):
         assert expected == parser.missing_arc_description(5, -5)
 
     def test_missing_arc_descriptions_for_exceptions(self):
-        parser = self.parse_text(u"""\
+        parser = self.parse_text("""\
             try:
                 pass
             except ZeroDivideError:
@@ -310,7 +310,7 @@ class ParserMissingArcDescriptionTest(CoverageTest):
         assert expected == parser.missing_arc_description(5, 6)
 
     def test_missing_arc_descriptions_for_finally(self):
-        parser = self.parse_text(u"""\
+        parser = self.parse_text("""\
             def function():
                 for i in range(2):
                     try:
@@ -384,7 +384,7 @@ class ParserMissingArcDescriptionTest(CoverageTest):
             assert expected == parser.missing_arc_description(18, -1)
 
     def test_missing_arc_descriptions_bug460(self):
-        parser = self.parse_text(u"""\
+        parser = self.parse_text("""\
             x = 1
             d = {
                 3: lambda: [],
diff --git a/tests/test_phystokens.py b/tests/test_phystokens.py
index 76b545e1..06cdd385 100644
--- a/tests/test_phystokens.py
+++ b/tests/test_phystokens.py
@@ -18,7 +18,7 @@ from tests.coveragetest import CoverageTest, TESTS_DIR
 
 
 # A simple program and its token stream.
-SIMPLE = u"""\
+SIMPLE = """\
 # yay!
 def foo():
   say('two = %d' % 2)
@@ -33,7 +33,7 @@ SIMPLE_TOKENS = [
 ]
 
 # Mixed-whitespace program, and its token stream.
-MIXED_WS = u"""\
+MIXED_WS = """\
 def hello():
         a="Hello world!"
 \tb="indented"
@@ -46,7 +46,7 @@ MIXED_WS_TOKENS = [
 ]
 
 # https://github.com/nedbat/coveragepy/issues/822
-BUG_822 = u"""\
+BUG_822 = """\
 print( "Message 1" )
 array = [ 1,2,3,4,       # 4 numbers \\
           5,6,7 ]        # 3 numbers
@@ -192,12 +192,12 @@ class NeuterEncodingDeclarationTest(CoverageTest):
             assert source_encoding(neutered) == DEF_ENCODING, "Wrong encoding in %r" % neutered
 
     def test_two_encoding_declarations(self):
-        input_src = textwrap.dedent(u"""\
+        input_src = textwrap.dedent("""\
             # -*- coding: ascii -*-
             # -*- coding: utf-8 -*-
             # -*- coding: utf-16 -*-
             """)
-        expected_src = textwrap.dedent(u"""\
+        expected_src = textwrap.dedent("""\
             # (deleted declaration) -*-
             # (deleted declaration) -*-
             # -*- coding: utf-16 -*-
@@ -206,12 +206,12 @@ class NeuterEncodingDeclarationTest(CoverageTest):
         assert expected_src == output_src
 
     def test_one_encoding_declaration(self):
-        input_src = textwrap.dedent(u"""\
+        input_src = textwrap.dedent("""\
             # -*- coding: utf-16 -*-
             # Just a comment.
             # -*- coding: ascii -*-
             """)
-        expected_src = textwrap.dedent(u"""\
+        expected_src = textwrap.dedent("""\
             # (deleted declaration) -*-
             # Just a comment.
             # -*- coding: ascii -*-
@@ -260,7 +260,7 @@ class CompileUnicodeTest(CoverageTest):
 
     def assert_compile_unicode(self, source):
         """Assert that `source` will compile properly with `compile_unicode`."""
-        source += u"a = 42\n"
+        source += "a = 42\n"
         # This doesn't raise an exception:
         code = compile_unicode(source, "<string>", "exec")
         globs = {}
@@ -268,11 +268,11 @@ class CompileUnicodeTest(CoverageTest):
         assert globs['a'] == 42
 
     def test_cp1252(self):
-        uni = u"""# coding: cp1252\n# \u201C curly \u201D\n"""
+        uni = """# coding: cp1252\n# \u201C curly \u201D\n"""
         self.assert_compile_unicode(uni)
 
     def test_double_coding_declaration(self):
         # Build this string in a weird way so that actual vim's won't try to
         # interpret it...
-        uni = u"# -*-  coding:utf-8 -*-\n# v" + "im: fileencoding=utf-8\n"
+        uni = "# -*-  coding:utf-8 -*-\n# v" + "im: fileencoding=utf-8\n"
         self.assert_compile_unicode(uni)
diff --git a/tests/test_plugins.py b/tests/test_plugins.py
index fec92749..21aeab14 100644
--- a/tests/test_plugins.py
+++ b/tests/test_plugins.py
@@ -22,7 +22,7 @@ from tests.coveragetest import CoverageTest
 from tests.helpers import CheckUniqueFilenames
 
 
-class FakeConfig(object):
+class FakeConfig:
     """A fake config for use in tests."""
 
     def __init__(self, plugin, options):
@@ -644,7 +644,7 @@ class BadFileTracerTest(FileTracerTest):
         #   Disabling plug-in '...' due to previous exception
         # or:
         #   Disabling plug-in '...' due to an exception:
-        msg = "Disabling plug-in '%s.%s' due to " % (module_name, plugin_name)
+        msg = f"Disabling plug-in '{module_name}.{plugin_name}' due to "
         warnings = stderr.count(msg)
         assert warnings == 1
 
diff --git a/tests/test_process.py b/tests/test_process.py
index a73c650f..b57a4aa4 100644
--- a/tests/test_process.py
+++ b/tests/test_process.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -162,9 +161,9 @@ class ProcessTest(CoverageTest):
         assert status == 1
 
         for n in "12":
-            self.assert_exists(".coverage.bad{}".format(n))
+            self.assert_exists(f".coverage.bad{n}")
             warning_regex = (
-                r"Coverage.py warning: Couldn't use data file '.*\.coverage.bad{0}': "
+                r"Coverage.py warning: Couldn't use data file '.*\.coverage.bad{}': "
                 r"file (is encrypted or )?is not a database"
                 .format(n)
             )
@@ -490,7 +489,7 @@ class ProcessTest(CoverageTest):
 
         # But also make sure that the output is what we expect.
         path = python_reported_file('throw.py')
-        msg = 'File "{}", line 5,? in f2'.format(re.escape(path))
+        msg = f'File "{re.escape(path)}", line 5,? in f2'
         assert re.search(msg, out)
         assert 'raise Exception("hey!")' in out
         assert status == 1
@@ -563,8 +562,8 @@ class ProcessTest(CoverageTest):
         # The two data files should have different random numbers at the end of
         # the file name.
         data_files = glob.glob(".coverage.*")
-        nums = set(name.rpartition(".")[-1] for name in data_files)
-        assert len(nums) == 2, "Same random: %s" % (data_files,)
+        nums = {name.rpartition(".")[-1] for name in data_files}
+        assert len(nums) == 2, f"Same random: {data_files}"
 
         # Combine the parallel coverage data files into .coverage .
         self.run_command("coverage combine")
@@ -604,7 +603,7 @@ class ProcessTest(CoverageTest):
         # will fail.
         out = self.run_command("coverage run i_dont_exist.py")
         path = python_reported_file('i_dont_exist.py')
-        assert "No file to run: '{}'".format(path) in out
+        assert f"No file to run: '{path}'" in out
         assert "warning" not in out
         assert "Exception" not in out
 
@@ -727,7 +726,7 @@ class ProcessTest(CoverageTest):
 
         msg = (
             "Coverage.py warning: "
-            "Already imported a file that will be measured: {0} "
+            "Already imported a file that will be measured: {} "
             "(already-imported)").format(goodbye_path)
         assert msg in out
 
@@ -990,7 +989,7 @@ class EnvironmentTest(CoverageTest):
             self.make_file("run_me.py", f.read())
         expected = self.run_command("python run_me.py")
         cov_main = os.path.join(TESTS_DIR, "covmain.zip")
-        actual = self.run_command("python {} run run_me.py".format(cov_main))
+        actual = self.run_command(f"python {cov_main} run run_me.py")
         self.assert_tryexecfile_output(expected, actual)
 
     def test_coverage_custom_script(self):
@@ -1217,7 +1216,7 @@ class FailUnderTest(CoverageTest):
     """Tests of the --fail-under switch."""
 
     def setup_test(self):
-        super(FailUnderTest, self).setup_test()
+        super().setup_test()
         self.make_file("forty_two_plus.py", """\
             # I have 42.857% (3/7) coverage!
             a = 1
@@ -1276,14 +1275,14 @@ class UnicodeFilePathsTest(CoverageTest):
 
     def test_accented_dot_py(self):
         # Make a file with a non-ascii character in the filename.
-        self.make_file(u"h\xe2t.py", "print('accented')")
-        out = self.run_command(u"coverage run --source=. h\xe2t.py")
+        self.make_file("h\xe2t.py", "print('accented')")
+        out = self.run_command("coverage run --source=. h\xe2t.py")
         assert out == "accented\n"
 
         # The HTML report uses ascii-encoded HTML entities.
         out = self.run_command("coverage html")
         assert out == ""
-        self.assert_exists(u"htmlcov/h\xe2t_py.html")
+        self.assert_exists("htmlcov/h\xe2t_py.html")
         with open("htmlcov/index.html") as indexf:
             index = indexf.read()
         assert '<a href="h&#226;t_py.html">h&#226;t.py</a>' in index
@@ -1293,15 +1292,15 @@ class UnicodeFilePathsTest(CoverageTest):
         assert out == ""
         with open("coverage.xml", "rb") as xmlf:
             xml = xmlf.read()
-        assert u' filename="h\xe2t.py"'.encode('utf8') in xml
-        assert u' name="h\xe2t.py"'.encode('utf8') in xml
+        assert ' filename="h\xe2t.py"'.encode() in xml
+        assert ' name="h\xe2t.py"'.encode() in xml
 
         report_expected = (
-            u"Name     Stmts   Miss  Cover\n"
-            u"----------------------------\n"
-            u"h\xe2t.py       1      0   100%\n"
-            u"----------------------------\n"
-            u"TOTAL        1      0   100%\n"
+            "Name     Stmts   Miss  Cover\n"
+            "----------------------------\n"
+            "h\xe2t.py       1      0   100%\n"
+            "----------------------------\n"
+            "TOTAL        1      0   100%\n"
         )
 
         out = self.run_command("coverage report")
@@ -1309,14 +1308,14 @@ class UnicodeFilePathsTest(CoverageTest):
 
     def test_accented_directory(self):
         # Make a file with a non-ascii character in the directory name.
-        self.make_file(u"\xe2/accented.py", "print('accented')")
-        out = self.run_command(u"coverage run --source=. \xe2/accented.py")
+        self.make_file("\xe2/accented.py", "print('accented')")
+        out = self.run_command("coverage run --source=. \xe2/accented.py")
         assert out == "accented\n"
 
         # The HTML report uses ascii-encoded HTML entities.
         out = self.run_command("coverage html")
         assert out == ""
-        self.assert_exists(u"htmlcov/\xe2_accented_py.html")
+        self.assert_exists("htmlcov/\xe2_accented_py.html")
         with open("htmlcov/index.html") as indexf:
             index = indexf.read()
         assert '<a href="&#226;_accented_py.html">&#226;%saccented.py</a>' % os.sep in index
@@ -1330,21 +1329,21 @@ class UnicodeFilePathsTest(CoverageTest):
         assert b' name="accented.py"' in xml
 
         dom = ElementTree.parse("coverage.xml")
-        elts = dom.findall(u".//package[@name='â']")
+        elts = dom.findall(".//package[@name='â']")
         assert len(elts) == 1
         assert elts[0].attrib == {
-            "branch-rate": u"0",
-            "complexity": u"0",
-            "line-rate": u"1",
-            "name": u"â",
+            "branch-rate": "0",
+            "complexity": "0",
+            "line-rate": "1",
+            "name": "â",
         }
 
         report_expected = (
-            u"Name            Stmts   Miss  Cover\n"
-            u"-----------------------------------\n"
-            u"\xe2%saccented.py       1      0   100%%\n"
-            u"-----------------------------------\n"
-            u"TOTAL               1      0   100%%\n"
+            "Name            Stmts   Miss  Cover\n"
+            "-----------------------------------\n"
+            "\xe2%saccented.py       1      0   100%%\n"
+            "-----------------------------------\n"
+            "TOTAL               1      0   100%%\n"
         ) % os.sep
 
         out = self.run_command("coverage report")
@@ -1400,11 +1399,11 @@ def possible_pth_dirs():
 def find_writable_pth_directory():
     """Find a place to write a .pth file."""
     for pth_dir in possible_pth_dirs():             # pragma: part covered
-        try_it = os.path.join(pth_dir, "touch_{}.it".format(WORKER))
+        try_it = os.path.join(pth_dir, f"touch_{WORKER}.it")
         with open(try_it, "w") as f:
             try:
                 f.write("foo")
-            except (IOError, OSError):              # pragma: cant happen
+            except OSError:              # pragma: cant happen
                 continue
 
         os.remove(try_it)
@@ -1427,19 +1426,19 @@ def persistent_remove(path):
             time.sleep(.05)
         else:
             return
-    raise Exception("Sorry, couldn't remove {!r}".format(path))     # pragma: cant happen
+    raise Exception(f"Sorry, couldn't remove {path!r}")     # pragma: cant happen
 
 
-class ProcessCoverageMixin(object):
+class ProcessCoverageMixin:
     """Set up a .pth file to coverage-measure all sub-processes."""
 
     def setup_test(self):
-        super(ProcessCoverageMixin, self).setup_test()
+        super().setup_test()
 
         # Create the .pth file.
         assert PTH_DIR
         pth_contents = "import coverage; coverage.process_startup()\n"
-        pth_path = os.path.join(PTH_DIR, "subcover_{}.pth".format(WORKER))
+        pth_path = os.path.join(PTH_DIR, f"subcover_{WORKER}.pth")
         with open(pth_path, "w") as pth:
             pth.write(pth_contents)
 
@@ -1451,7 +1450,7 @@ class ProcessStartupTest(ProcessCoverageMixin, CoverageTest):
     """Test that we can measure coverage in sub-processes."""
 
     def setup_test(self):
-        super(ProcessStartupTest, self).setup_test()
+        super().setup_test()
 
         # Main will run sub.py
         self.make_file("main.py", """\
@@ -1688,7 +1687,7 @@ def venv_world_fixture(tmp_path_factory):
 
         # Install coverage.
         coverage_src = nice_file(TESTS_DIR, "..")
-        run_in_venv("python -m pip install --no-index {}".format(coverage_src))
+        run_in_venv(f"python -m pip install --no-index {coverage_src}")
 
     return venv_world
 
diff --git a/tests/test_setup.py b/tests/test_setup.py
index b2ccd67c..0d64319c 100644
--- a/tests/test_setup.py
+++ b/tests/test_setup.py
@@ -16,7 +16,7 @@ class SetupPyTest(CoverageTest):
     run_in_temp_dir = False
 
     def setup_test(self):
-        super(SetupPyTest, self).setup_test()
+        super().setup_test()
         # Force the most restrictive interpretation.
         self.set_environ('LC_ALL', 'C')
 
diff --git a/tests/test_summary.py b/tests/test_summary.py
index b00ee96b..a326fc85 100644
--- a/tests/test_summary.py
+++ b/tests/test_summary.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -105,8 +104,8 @@ class SummaryTest(UsingModulesMixin, CoverageTest):
         # Try reporting while omitting some modules
         self.make_mycode()
         self.run_command("coverage run mycode.py")
-        omit = '{}/*,*/site-packages/*'.format(TESTS_DIR)
-        report = self.report_from_command("coverage report --omit '{}'".format(omit))
+        omit = f'{TESTS_DIR}/*,*/site-packages/*'
+        report = self.report_from_command(f"coverage report --omit '{omit}'")
 
         # Name        Stmts   Miss  Cover
         # -------------------------------
@@ -569,10 +568,10 @@ class SummaryTest(UsingModulesMixin, CoverageTest):
         # We run a .py file with a non-ascii name, and when reporting, we can't
         # parse it as Python.  We should get an error message in the report.
 
-        self.make_file(u"accented\xe2.py", "print('accented')")
-        self.run_command(u"coverage run accented\xe2.py")
-        self.make_file(u"accented\xe2.py", "This isn't python at all!")
-        report = self.report_from_command(u"coverage report accented\xe2.py")
+        self.make_file("accented\xe2.py", "print('accented')")
+        self.run_command("coverage run accented\xe2.py")
+        self.make_file("accented\xe2.py", "This isn't python at all!")
+        report = self.report_from_command("coverage report accented\xe2.py")
 
         # Couldn't parse '...' as Python source: 'invalid syntax' at line 1
         # Name     Stmts   Miss  Cover
@@ -584,7 +583,7 @@ class SummaryTest(UsingModulesMixin, CoverageTest):
         errmsg = re.sub(r"parse '.*(accented.*?\.py)", r"parse '\1", errmsg)
         # The actual error message varies version to version
         errmsg = re.sub(r": '.*' at", ": 'error' at", errmsg)
-        expected = u"Couldn't parse 'accented\xe2.py' as Python source: 'error' at line 1"
+        expected = "Couldn't parse 'accented\xe2.py' as Python source: 'error' at line 1"
         assert expected == errmsg
 
     def test_dotpy_not_python_ignored(self):
@@ -903,7 +902,7 @@ class SummaryReporterConfigurationTest(CoverageTest):
         """Assert that the `words` appear in order in `text`."""
         indexes = list(map(text.find, words))
         assert -1 not in indexes
-        msg = "The words %r don't appear in order in %r" % (words, text)
+        msg = f"The words {words!r} don't appear in order in {text!r}"
         assert indexes == sorted(indexes), msg
 
     def test_sort_report_by_stmts(self):
diff --git a/tests/test_templite.py b/tests/test_templite.py
index 770e97f9..e4d83647 100644
--- a/tests/test_templite.py
+++ b/tests/test_templite.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -14,7 +13,7 @@ from tests.coveragetest import CoverageTest
 
 # pylint: disable=possibly-unused-variable
 
-class AnyOldObject(object):
+class AnyOldObject:
     """Simple testing object.
 
     Use keyword arguments in the constructor to set attributes on the object.
@@ -289,9 +288,9 @@ class TempliteTest(CoverageTest):
 
     def test_non_ascii(self):
         self.try_render(
-            u"{{where}} ollǝɥ",
-            { 'where': u'ǝɹǝɥʇ' },
-            u"ǝɹǝɥʇ ollǝɥ"
+            "{{where}} ollǝɥ",
+            { 'where': 'ǝɹǝɥʇ' },
+            "ǝɹǝɥʇ ollǝɥ"
         )
 
     def test_exception_during_evaluation(self):
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 558c846e..3a563efe 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -209,7 +208,7 @@ class CheckUniqueFilenamesTest(CoverageTest):
 
     run_in_temp_dir = False
 
-    class Stub(object):
+    class Stub:
         """A stand-in for the class we're checking."""
         def __init__(self, x):
             self.x = x
diff --git a/tests/test_xml.py b/tests/test_xml.py
index 334abb4c..9c6cfb58 100644
--- a/tests/test_xml.py
+++ b/tests/test_xml.py
@@ -1,4 +1,3 @@
-# coding: utf-8
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
@@ -54,13 +53,13 @@ class XmlTestHelpers(CoverageTest):
             return os.path.join(curdir, p)
 
         for i in range(width):
-            next_dir = here("d{}".format(i))
+            next_dir = here(f"d{i}")
             self.make_tree(width, depth-1, next_dir)
         if curdir != ".":
             self.make_file(here("__init__.py"), "")
             for i in range(width):
-                filename = here("f{}.py".format(i))
-                self.make_file(filename, "# {}\n".format(filename))
+                filename = here(f"f{i}.py")
+                self.make_file(filename, f"# {filename}\n")
 
     def assert_source(self, xmldom, src):
         """Assert that the XML has a <source> element with `src`."""