diff --git a/testing/acceptance_test.py b/testing/acceptance_test.py
index ad9c37737a..c826996516 100644
--- a/testing/acceptance_test.py
+++ b/testing/acceptance_test.py
@@ -246,7 +246,7 @@ def test_issue93_initialnode_importing_capturing(self, testdir):
         )
         result = testdir.runpytest()
         assert result.ret == ExitCode.NO_TESTS_COLLECTED
-        assert "should not be seen" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*should not be seen*")
         assert "stderr42" not in result.stderr.str()
 
     def test_conftest_printing_shows_if_error(self, testdir):
@@ -954,7 +954,7 @@ def test_with_failing_collection(self, testdir):
         result.stdout.fnmatch_lines(["*Interrupted: 1 errors during collection*"])
         # Collection errors abort test execution, therefore no duration is
         # output
-        assert "duration" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*duration*")
 
     def test_with_not(self, testdir):
         testdir.makepyfile(self.source)
@@ -1008,7 +1008,7 @@ def main():
     result = testdir.runpython(target)
     assert result.ret == 0
     result.stderr.fnmatch_lines(["*not found*foo*"])
-    assert "INTERNALERROR>" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR>*")
 
 
 def test_import_plugin_unicode_name(testdir):
diff --git a/testing/code/test_excinfo.py b/testing/code/test_excinfo.py
index 5673b811b9..e48ea86142 100644
--- a/testing/code/test_excinfo.py
+++ b/testing/code/test_excinfo.py
@@ -399,7 +399,7 @@ def test_division_zero():
     result = testdir.runpytest()
     assert result.ret != 0
     result.stdout.fnmatch_lines(["*AssertionError*Pattern*[123]*not found*"])
-    assert "__tracebackhide__ = True" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*__tracebackhide__ = True*")
 
     result = testdir.runpytest("--fulltrace")
     assert result.ret != 0
@@ -1343,7 +1343,7 @@ def test(tmpdir):
     )
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(["* 1 failed in *"])
-    assert "INTERNALERROR" not in result.stdout.str() + result.stderr.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*") + result.stderr.str()
 
 
 @pytest.mark.usefixtures("limited_recursion_depth")
diff --git a/testing/logging/test_fixture.py b/testing/logging/test_fixture.py
index 5d2ff4654d..c68866beff 100644
--- a/testing/logging/test_fixture.py
+++ b/testing/logging/test_fixture.py
@@ -46,7 +46,7 @@ def test2(caplog):
     )
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(["*log from test1*", "*2 failed in *"])
-    assert "log from test2" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*log from test2*")
 
 
 def test_with_statement(caplog):
diff --git a/testing/logging/test_reporting.py b/testing/logging/test_reporting.py
index 1ae0bd7833..5b24ef963a 100644
--- a/testing/logging/test_reporting.py
+++ b/testing/logging/test_reporting.py
@@ -109,7 +109,7 @@ def test_foo():
             "=* 1 failed in *=",
         ]
     )
-    assert "DEBUG" not in result.stdout.str()
+    result.stdout.no_re_match_line("DEBUG")
 
 
 def test_setup_logging(testdir):
@@ -282,7 +282,7 @@ def test_log_cli(request):
             "WARNING*test_log_cli_default_level.py* message will be shown*",
         ]
     )
-    assert "INFO message won't be shown" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INFO message won't be shown*")
     # make sure that that we get a '0' exit code for the testsuite
     assert result.ret == 0
 
@@ -566,7 +566,7 @@ def test_log_cli(request):
             "PASSED",  # 'PASSED' on its own line because the log message prints a new line
         ]
     )
-    assert "This log message won't be shown" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*This log message won't be shown*")
 
     # make sure that that we get a '0' exit code for the testsuite
     assert result.ret == 0
@@ -580,7 +580,7 @@ def test_log_cli(request):
             "PASSED",  # 'PASSED' on its own line because the log message prints a new line
         ]
     )
-    assert "This log message won't be shown" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*This log message won't be shown*")
 
     # make sure that that we get a '0' exit code for the testsuite
     assert result.ret == 0
@@ -616,7 +616,7 @@ def test_log_cli(request):
             "PASSED",  # 'PASSED' on its own line because the log message prints a new line
         ]
     )
-    assert "This log message won't be shown" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*This log message won't be shown*")
 
     # make sure that that we get a '0' exit code for the testsuite
     assert result.ret == 0
@@ -942,7 +942,7 @@ def test_simple():
             ]
         )
     elif verbose == "-q":
-        assert "collected 1 item*" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*collected 1 item**")
         expected_lines.extend(
             [
                 "*test_collection_collect_only_live_logging.py::test_simple*",
@@ -950,7 +950,7 @@ def test_simple():
             ]
         )
     elif verbose == "-qq":
-        assert "collected 1 item*" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*collected 1 item**")
         expected_lines.extend(["*test_collection_collect_only_live_logging.py: 1*"])
 
     result.stdout.fnmatch_lines(expected_lines)
@@ -983,7 +983,7 @@ def test_simple():
 
     result = testdir.runpytest()
 
-    assert "--- live log collection ---" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*--- live log collection ---*")
 
     assert result.ret == 0
     assert os.path.isfile(log_file)
diff --git a/testing/python/collect.py b/testing/python/collect.py
index e6dd3e8708..8fc882f88a 100644
--- a/testing/python/collect.py
+++ b/testing/python/collect.py
@@ -1139,7 +1139,7 @@ class Test(object):
     """
     )
     result = testdir.runpytest()
-    assert "TypeError" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*TypeError*")
     assert result.ret == ExitCode.NO_TESTS_COLLECTED
 
 
diff --git a/testing/python/fixtures.py b/testing/python/fixtures.py
index f4dbfdf097..7bacfb6e24 100644
--- a/testing/python/fixtures.py
+++ b/testing/python/fixtures.py
@@ -455,7 +455,7 @@ def test_lookup_error(unknown):
                 "*1 error*",
             ]
         )
-        assert "INTERNAL" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*INTERNAL*")
 
     def test_fixture_excinfo_leak(self, testdir):
         # on python2 sys.excinfo would leak into fixture executions
@@ -2647,7 +2647,7 @@ def test_finish():
             *3 passed*
         """
         )
-        assert "error" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*error*")
 
     def test_fixture_finalizer(self, testdir):
         testdir.makeconftest(
@@ -3151,7 +3151,7 @@ def arg1():
             *hello world*
         """
         )
-        assert "arg0" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*arg0*")
 
     @pytest.mark.parametrize("testmod", [True, False])
     def test_show_fixtures_conftest(self, testdir, testmod):
diff --git a/testing/python/setup_only.py b/testing/python/setup_only.py
index 4ae24b15a6..40881caab4 100644
--- a/testing/python/setup_only.py
+++ b/testing/python/setup_only.py
@@ -27,7 +27,7 @@ def test_arg1(arg1):
     result.stdout.fnmatch_lines(
         ["*SETUP    F arg1*", "*test_arg1 (fixtures used: arg1)*", "*TEARDOWN F arg1*"]
     )
-    assert "_arg0" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*_arg0*")
 
 
 def test_show_different_scopes(testdir, mode):
diff --git a/testing/python/show_fixtures_per_test.py b/testing/python/show_fixtures_per_test.py
index aff8aa0e5e..ef841819d0 100644
--- a/testing/python/show_fixtures_per_test.py
+++ b/testing/python/show_fixtures_per_test.py
@@ -1,6 +1,6 @@
 def test_no_items_should_not_show_output(testdir):
     result = testdir.runpytest("--fixtures-per-test")
-    assert "fixtures used by" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*fixtures used by*")
     assert result.ret == 0
 
 
@@ -30,7 +30,7 @@ def test_arg1(arg1):
             "    arg1 docstring",
         ]
     )
-    assert "_arg0" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*_arg0*")
 
 
 def test_fixtures_in_conftest(testdir):
diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index bf23e32023..96178452a7 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -1033,7 +1033,7 @@ def test_hello():
     result = testdir.runpytest()
     assert "3 == 4" in result.stdout.str()
     result = testdir.runpytest_subprocess("--assert=plain")
-    assert "3 == 4" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*3 == 4*")
 
 
 def test_triple_quoted_string_issue113(testdir):
@@ -1045,7 +1045,7 @@ def test_hello():
     )
     result = testdir.runpytest("--fulltrace")
     result.stdout.fnmatch_lines(["*1 failed*"])
-    assert "SyntaxError" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*SyntaxError*")
 
 
 def test_traceback_failure(testdir):
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index 89b23a72c7..470c54145e 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -914,7 +914,7 @@ def test_rewrite_warning_using_pytest_plugins(self, testdir):
         testdir.chdir()
         result = testdir.runpytest_subprocess()
         result.stdout.fnmatch_lines(["*= 1 passed in *=*"])
-        assert "pytest-warning summary" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*pytest-warning summary*")
 
     def test_rewrite_warning_using_pytest_plugins_env_var(self, testdir, monkeypatch):
         monkeypatch.setenv("PYTEST_PLUGINS", "plugin")
@@ -932,7 +932,7 @@ def test():
         testdir.chdir()
         result = testdir.runpytest_subprocess()
         result.stdout.fnmatch_lines(["*= 1 passed in *=*"])
-        assert "pytest-warning summary" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*pytest-warning summary*")
 
 
 class TestAssertionRewriteHookDetails:
@@ -1124,7 +1124,7 @@ def test_long_repr():
     """
     )
     result = testdir.runpytest()
-    assert "unbalanced braces" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*unbalanced braces*")
 
 
 class TestIssue925:
diff --git a/testing/test_cacheprovider.py b/testing/test_cacheprovider.py
index cbba27e5f5..e2fd5a4ca5 100644
--- a/testing/test_cacheprovider.py
+++ b/testing/test_cacheprovider.py
@@ -327,7 +327,7 @@ def test_always_fails():
         result = testdir.runpytest("--lf", "--ff")
         # Test order will be failing tests firs
         result.stdout.fnmatch_lines(["test_b.py*"])
-        assert "test_a.py" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*test_a.py*")
 
     def test_lastfailed_difference_invocations(self, testdir, monkeypatch):
         monkeypatch.setenv("PYTHONDONTWRITEBYTECODE", "1")
@@ -660,11 +660,11 @@ def test_lf_and_ff_prints_no_needless_message(self, quiet, opt, testdir):
         if quiet:
             args.append("-q")
         result = testdir.runpytest(*args)
-        assert "run all" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*run all*")
 
         result = testdir.runpytest(*args)
         if quiet:
-            assert "run all" not in result.stdout.str()
+            result.stdout.no_fnmatch_line("*run all*")
         else:
             assert "rerun previous" in result.stdout.str()
 
diff --git a/testing/test_capture.py b/testing/test_capture.py
index f5b193597f..0f7db4b8e9 100644
--- a/testing/test_capture.py
+++ b/testing/test_capture.py
@@ -609,12 +609,12 @@ def test_normal():
             *while capture is disabled*
         """
         )
-        assert "captured before" not in result.stdout.str()
-        assert "captured after" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*captured before*")
+        result.stdout.no_fnmatch_line("*captured after*")
         if no_capture:
             assert "test_normal executed" in result.stdout.str()
         else:
-            assert "test_normal executed" not in result.stdout.str()
+            result.stdout.no_fnmatch_line("*test_normal executed*")
 
     @pytest.mark.parametrize("fixture", ["capsys", "capfd"])
     def test_fixture_use_by_other_fixtures(self, testdir, fixture):
@@ -650,8 +650,8 @@ def test_captured_print(captured_print):
         )
         result = testdir.runpytest_subprocess()
         result.stdout.fnmatch_lines(["*1 passed*"])
-        assert "stdout contents begin" not in result.stdout.str()
-        assert "stderr contents begin" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*stdout contents begin*")
+        result.stdout.no_fnmatch_line("*stderr contents begin*")
 
     @pytest.mark.parametrize("cap", ["capsys", "capfd"])
     def test_fixture_use_by_other_fixtures_teardown(self, testdir, cap):
@@ -721,7 +721,7 @@ def pytest_runtest_setup():
     testdir.makepyfile("def test_func(): pass")
     result = testdir.runpytest()
     assert result.ret == 0
-    assert "hello19" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*hello19*")
 
 
 def test_capture_badoutput_issue412(testdir):
@@ -1388,7 +1388,7 @@ def test_spam_in_thread():
     result = testdir.runpytest_subprocess(str(p))
     assert result.ret == 0
     assert result.stderr.str() == ""
-    assert "IOError" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*IOError*")
 
 
 def test_pickling_and_unpickling_encoded_file():
diff --git a/testing/test_collection.py b/testing/test_collection.py
index dee07d5c71..7a5cf795b2 100644
--- a/testing/test_collection.py
+++ b/testing/test_collection.py
@@ -139,7 +139,7 @@ def test_ignored_virtualenvs(self, testdir, fname):
 
         # by default, ignore tests inside a virtualenv
         result = testdir.runpytest()
-        assert "test_invenv" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*test_invenv*")
         # allow test collection if user insists
         result = testdir.runpytest("--collect-in-virtualenv")
         assert "test_invenv" in result.stdout.str()
@@ -165,7 +165,7 @@ def test_ignored_virtualenvs_norecursedirs_precedence(self, testdir, fname):
         testfile = testdir.tmpdir.ensure(".virtual", "test_invenv.py")
         testfile.write("def test_hello(): pass")
         result = testdir.runpytest("--collect-in-virtualenv")
-        assert "test_invenv" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*test_invenv*")
         # ...unless the virtualenv is explicitly given on the CLI
         result = testdir.runpytest("--collect-in-virtualenv", ".virtual")
         assert "test_invenv" in result.stdout.str()
@@ -364,7 +364,7 @@ def pytest_configure(config):
         testdir.makepyfile(test_world="def test_hello(): pass")
         result = testdir.runpytest()
         assert result.ret == ExitCode.NO_TESTS_COLLECTED
-        assert "passed" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*passed*")
         result = testdir.runpytest("--XX")
         assert result.ret == 0
         assert "passed" in result.stdout.str()
@@ -857,7 +857,7 @@ def test_exit_on_collection_with_maxfail_smaller_than_n_errors(testdir):
         ["*ERROR collecting test_02_import_error.py*", "*No module named *asdfa*"]
     )
 
-    assert "test_03" not in res.stdout.str()
+    res.stdout.no_fnmatch_line("*test_03*")
 
 
 def test_exit_on_collection_with_maxfail_bigger_than_n_errors(testdir):
@@ -996,12 +996,12 @@ def test_collect_init_tests(testdir):
     result.stdout.fnmatch_lines(
         ["<Package */tests>", "  <Module test_foo.py>", "    <Function test_foo>"]
     )
-    assert "test_init" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*test_init*")
     result = testdir.runpytest("./tests/__init__.py", "--collect-only")
     result.stdout.fnmatch_lines(
         ["<Package */tests>", "  <Module __init__.py>", "    <Function test_init>"]
     )
-    assert "test_foo" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*test_foo*")
 
 
 def test_collect_invalid_signature_message(testdir):
diff --git a/testing/test_conftest.py b/testing/test_conftest.py
index 3f08ee3816..0374db0b35 100644
--- a/testing/test_conftest.py
+++ b/testing/test_conftest.py
@@ -187,7 +187,7 @@ def pytest_addoption(parser):
     )
     result = testdir.runpytest("-h", "--confcutdir=%s" % x, x)
     result.stdout.fnmatch_lines(["*--xyz*"])
-    assert "warning: could not load initial" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*warning: could not load initial*")
 
 
 @pytest.mark.skipif(
@@ -648,5 +648,5 @@ def pytest_addoption(parser):
         )
     )
     result = testdir.runpytest("-h", x)
-    assert "argument --xyz is required" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*argument --xyz is required*")
     assert "general:" in result.stdout.str()
diff --git a/testing/test_doctest.py b/testing/test_doctest.py
index 4aac5432d5..15455e672a 100644
--- a/testing/test_doctest.py
+++ b/testing/test_doctest.py
@@ -239,8 +239,8 @@ def foo():
             ]
         )
         # lines below should be trimmed out
-        assert "text-line-2" not in result.stdout.str()
-        assert "text-line-after" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*text-line-2*")
+        result.stdout.no_fnmatch_line("*text-line-after*")
 
     def test_docstring_full_context_around_error(self, testdir):
         """Test that we show the whole context before the actual line of a failing
@@ -1177,7 +1177,7 @@ def auto(request):
             """
             )
         result = testdir.runpytest("--doctest-modules")
-        assert "FAILURES" not in str(result.stdout.str())
+        str(result.stdout.no_fnmatch_line("*FAILURES*"))
         result.stdout.fnmatch_lines(["*=== 1 passed in *"])
 
     @pytest.mark.parametrize("scope", SCOPES)
@@ -1209,7 +1209,7 @@ def auto(request):
         """
         )
         result = testdir.runpytest("--doctest-modules")
-        assert "FAILURES" not in str(result.stdout.str())
+        str(result.stdout.no_fnmatch_line("*FAILURES*"))
         result.stdout.fnmatch_lines(["*=== 1 passed in *"])
 
 
diff --git a/testing/test_junitxml.py b/testing/test_junitxml.py
index d4a1f6cc31..06a0334896 100644
--- a/testing/test_junitxml.py
+++ b/testing/test_junitxml.py
@@ -1216,7 +1216,7 @@ def test_pass():
     )
 
     result, dom = run_and_parse(f, f)
-    assert "INTERNALERROR" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*")
     first, second = [x["classname"] for x in dom.find_by_tag("testcase")]
     assert first == second
 
@@ -1231,7 +1231,7 @@ def test_pass():
     )
 
     result, dom = run_and_parse(f, "--dist", "each", "--tx", "2*popen")
-    assert "INTERNALERROR" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*")
     first, second = [x["classname"] for x in dom.find_by_tag("testcase")]
     assert first == second
 
@@ -1271,7 +1271,7 @@ def test_pass():
 
     result, dom = run_and_parse()
 
-    assert "INTERNALERROR" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*")
 
     items = sorted("%(classname)s %(name)s" % x for x in dom.find_by_tag("testcase"))
     import pprint
diff --git a/testing/test_runner.py b/testing/test_runner.py
index 82e413518f..9920d2b3e9 100644
--- a/testing/test_runner.py
+++ b/testing/test_runner.py
@@ -615,7 +615,7 @@ def teardown_function(function):
     )
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(["world", "hello"])
-    assert "def teardown_function" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*def teardown_function*")
 
 
 def test_pytest_fail_notrace_collection(testdir):
@@ -630,7 +630,7 @@ def some_internal_function():
     )
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(["hello"])
-    assert "def some_internal_function()" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*def some_internal_function()*")
 
 
 def test_pytest_fail_notrace_non_ascii(testdir):
@@ -648,7 +648,7 @@ def test_hello():
     )
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(["*test_hello*", "oh oh: ☺"])
-    assert "def test_hello" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*def test_hello*")
 
 
 def test_pytest_no_tests_collected_exit_status(testdir):
@@ -813,7 +813,7 @@ def test_func():
     """
     )
     result = testdir.runpytest("--tb=line")
-    assert "def setup_module" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*def setup_module*")
 
 
 def test_makereport_getsource(testdir):
@@ -825,7 +825,7 @@ def test_foo():
     """
     )
     result = testdir.runpytest()
-    assert "INTERNALERROR" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*")
     result.stdout.fnmatch_lines(["*else: assert False*"])
 
 
@@ -856,7 +856,7 @@ def test_fix(foo):
     """
     )
     result = testdir.runpytest("-vv")
-    assert "INTERNALERROR" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*INTERNALERROR*")
     result.stdout.fnmatch_lines(["*test_fix*", "*fixture*'missing'*not found*"])
 
 
diff --git a/testing/test_runner_xunit.py b/testing/test_runner_xunit.py
index 34a086551f..1e63bbf49d 100644
--- a/testing/test_runner_xunit.py
+++ b/testing/test_runner_xunit.py
@@ -237,7 +237,7 @@ def test_function2(hello):
             "*2 error*",
         ]
     )
-    assert "xyz43" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*xyz43*")
 
 
 @pytest.mark.parametrize("arg", ["", "arg"])
diff --git a/testing/test_skipping.py b/testing/test_skipping.py
index 8bba479f1b..51b1bbdd6a 100644
--- a/testing/test_skipping.py
+++ b/testing/test_skipping.py
@@ -949,7 +949,7 @@ def test_func():
     result = testdir.runpytest(p)
     assert result.ret == 0
     assert "xfailed" in result.stdout.str()
-    assert "xpassed" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*xpassed*")
 
 
 def test_imperativeskip_on_xfail_test(testdir):
diff --git a/testing/test_terminal.py b/testing/test_terminal.py
index 88f96f8940..3bdabc5dee 100644
--- a/testing/test_terminal.py
+++ b/testing/test_terminal.py
@@ -204,7 +204,7 @@ def test_method(self):
         result = testdir.runpytest("-vv")
         assert result.ret == 0
         result.stdout.fnmatch_lines(["*a123/test_hello123.py*PASS*"])
-        assert " <- " not in result.stdout.str()
+        result.stdout.no_fnmatch_line("* <- *")
 
     def test_keyboard_interrupt(self, testdir, option):
         testdir.makepyfile(
@@ -559,7 +559,7 @@ def test_pass():
                 "*= 2 passed, 1 deselected in * =*",
             ]
         )
-        assert "= 1 deselected =" not in result.stdout.str()
+        result.stdout.no_fnmatch_line("*= 1 deselected =*")
         assert result.ret == 0
 
     def test_no_skip_summary_if_failure(self, testdir):
@@ -759,7 +759,7 @@ def test_fail_extra_reporting(testdir, monkeypatch):
     monkeypatch.setenv("COLUMNS", "80")
     testdir.makepyfile("def test_this(): assert 0, 'this_failed' * 100")
     result = testdir.runpytest()
-    assert "short test summary" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*short test summary*")
     result = testdir.runpytest("-rf")
     result.stdout.fnmatch_lines(
         [
@@ -772,13 +772,13 @@ def test_fail_extra_reporting(testdir, monkeypatch):
 def test_fail_reporting_on_pass(testdir):
     testdir.makepyfile("def test_this(): assert 1")
     result = testdir.runpytest("-rf")
-    assert "short test summary" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*short test summary*")
 
 
 def test_pass_extra_reporting(testdir):
     testdir.makepyfile("def test_this(): assert 1")
     result = testdir.runpytest()
-    assert "short test summary" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*short test summary*")
     result = testdir.runpytest("-rp")
     result.stdout.fnmatch_lines(["*test summary*", "PASS*test_pass_extra_reporting*"])
 
@@ -786,7 +786,7 @@ def test_pass_extra_reporting(testdir):
 def test_pass_reporting_on_fail(testdir):
     testdir.makepyfile("def test_this(): assert 0")
     result = testdir.runpytest("-rp")
-    assert "short test summary" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*short test summary*")
 
 
 def test_pass_output_reporting(testdir):
@@ -829,7 +829,7 @@ def test_color_no(testdir):
     testdir.makepyfile("def test_this(): assert 1")
     result = testdir.runpytest("--color=no")
     assert "test session starts" in result.stdout.str()
-    assert "\x1b[1m" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*\x1b[1m*")
 
 
 @pytest.mark.parametrize("verbose", [True, False])
@@ -851,7 +851,7 @@ def test_this(i):
     result = testdir.runpytest(*args)
     assert "test session starts" in result.stdout.str()
     assert "\x1b[1m" in result.stdout.str()
-    assert "collecting 10 items" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*collecting 10 items*")
     if verbose:
         assert "collecting ..." in result.stdout.str()
     assert "collected 10 items" in result.stdout.str()
@@ -1214,7 +1214,7 @@ def test_failure():
             "*== 1 failed, 2 warnings in *",
         ]
     )
-    assert "None" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*None*")
     stdout = result.stdout.str()
     assert stdout.count("warning_from_test") == 1
     assert stdout.count("=== warnings summary ") == 2
@@ -1239,7 +1239,7 @@ def test_failure():
             "*== 1 failed, 1 warnings in *",
         ]
     )
-    assert "None" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*None*")
     stdout = result.stdout.str()
     assert stdout.count("warning_from_test") == 1
     assert stdout.count("=== warnings summary ") == 1
@@ -1402,7 +1402,7 @@ def pytest_collection_modifyitems(items, config):
         """
         )
         output = testdir.runpytest()
-        assert "ZeroDivisionError" not in output.stdout.str()
+        output.stdout.no_fnmatch_line("*ZeroDivisionError*")
         output.stdout.fnmatch_lines(["=* 2 passed in *="])
 
     def test_normal(self, many_tests_files, testdir):
@@ -1494,7 +1494,7 @@ def test_capture_no(self, many_tests_files, testdir):
         )
 
         output = testdir.runpytest("--capture=no")
-        assert "%]" not in output.stdout.str()
+        output.stdout.no_fnmatch_line("*%]*")
 
 
 class TestProgressWithTeardown:
diff --git a/testing/test_unittest.py b/testing/test_unittest.py
index 9b1b688ff8..281c852814 100644
--- a/testing/test_unittest.py
+++ b/testing/test_unittest.py
@@ -270,7 +270,7 @@ def test_method(self):
     result = testdir.runpytest("-s")
     assert result.ret == 1
     result.stdout.fnmatch_lines(["*setUp*", "*assert 0*down1*", "*1 failed*"])
-    assert "never42" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*never42*")
 
 
 def test_setup_setUpClass(testdir):
@@ -342,7 +342,7 @@ def test_hello(self):
         % (type, type)
     )
     result = testdir.runpytest()
-    assert "should not raise" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*should not raise*")
 
 
 @pytest.mark.parametrize("type", ["Error", "Failure"])
@@ -684,7 +684,7 @@ def test_hello(self):
     """
     )
     res = testdir.runpytest()
-    assert "failUnlessEqual" not in res.stdout.str()
+    res.stdout.no_fnmatch_line("*failUnlessEqual*")
 
 
 def test_unorderable_types(testdir):
@@ -703,7 +703,7 @@ class Test(unittest.TestCase):
     """
     )
     result = testdir.runpytest()
-    assert "TypeError" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*TypeError*")
     assert result.ret == ExitCode.NO_TESTS_COLLECTED
 
 
@@ -1020,7 +1020,7 @@ def test_hello(self):
     )
     result = testdir.runpytest()
     assert "should raise this exception" in result.stdout.str()
-    assert "ERROR at teardown of MyTestCase.test_hello" not in result.stdout.str()
+    result.stdout.no_fnmatch_line("*ERROR at teardown of MyTestCase.test_hello*")
 
 
 def test_error_message_with_parametrized_fixtures(testdir):