refactor: remove reliance on unittest_mixins.StdStreamCapturingMixin

This is another step toward removing unittest.TestCase as a base class.

6 files changed, 62 insertions, 26 deletions

diff --git a/tests/coveragetest.py b/tests/coveragetest.py
index eeabfb46..71f4e2c8 100644
--- a/tests/coveragetest.py
+++ b/tests/coveragetest.py
@@ -15,7 +15,7 @@ import shlex
 import sys
 
 import pytest
-from unittest_mixins import EnvironmentAwareMixin, StdStreamCapturingMixin, TempDirMixin
+from unittest_mixins import EnvironmentAwareMixin, TempDirMixin
 
 import coverage
 from coverage import env
@@ -25,7 +25,7 @@ from coverage.cmdline import CoverageScript
 
 from tests.helpers import arcs_to_arcz_repr, arcz_to_arcs
 from tests.helpers import run_command, SuperModuleCleaner
-from tests.mixins import StopEverythingMixin
+from tests.mixins import StdStreamCapturingMixin, StopEverythingMixin
 
 
 # Status returns for the command line.
diff --git a/tests/mixins.py b/tests/mixins.py
index 97ca093c..ab0623c0 100644
--- a/tests/mixins.py
+++ b/tests/mixins.py
@@ -10,6 +10,8 @@ Some of these are transitional while working toward pure-pytest style.
 import functools
 import types
 
+import pytest
+
 from coverage.backunittest import unittest
 from coverage.misc import StopEverything
 
@@ -37,3 +39,32 @@ class SkipConvertingMetaclass(type):
 
 
 StopEverythingMixin = SkipConvertingMetaclass('StopEverythingMixin', (), {})
+
+
+class StdStreamCapturingMixin:
+    """
+    Adapter from the pytest capsys fixture to more convenient methods.
+
+    This doesn't also output to the real stdout, so we probably want to move
+    to "real" capsys when we can use fixtures in test methods.
+
+    Once you've used one of these methods, the capturing is reset, so another
+    invocation will only return the delta.
+
+    """
+    @pytest.fixture(autouse=True)
+    def _capcapsys(self, capsys):
+        """Grab the fixture so our methods can use it."""
+        self.capsys = capsys
+
+    def stdouterr(self):
+        """Returns (out, err), two strings for stdout and stderr."""
+        return self.capsys.readouterr()
+
+    def stdout(self):
+        """Returns a string, the captured stdout."""
+        return self.capsys.readouterr().out
+
+    def stderr(self):
+        """Returns a string, the captured stderr."""
+        return self.capsys.readouterr().err
diff --git a/tests/test_api.py b/tests/test_api.py
index 6c322795..ea625ff1 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -520,10 +520,8 @@ class ApiTest(CoverageTest):
         self.start_import_stop(cov, "hello")
         cov.get_data()
 
-        out = self.stdout()
+        out, err = self.stdouterr()
         assert "Hello\n" in out
-
-        err = self.stderr()
         assert textwrap.dedent("""\
             Coverage.py warning: Module sys has no Python source. (module-not-python)
             Coverage.py warning: Module xyzzy was never imported. (module-not-imported)
@@ -544,10 +542,8 @@ class ApiTest(CoverageTest):
         self.start_import_stop(cov, "hello")
         cov.get_data()
 
-        out = self.stdout()
+        out, err = self.stdouterr()
         assert "Hello\n" in out
-
-        err = self.stderr()
         assert "Coverage.py warning: Module sys has no Python source. (module-not-python)" in err
         assert "module-not-imported" not in err
         assert "no-data-collected" not in err
diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index 3b63bcc2..66777751 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -1370,7 +1370,8 @@ class MiscArcTest(CoverageTest):
         # opcodes.
         # Note that we no longer interpret bytecode at all, but it couldn't
         # hurt to keep the test...
-        for n in [10, 50, 100, 500, 1000, 2000]:
+        sizes = [10, 50, 100, 500, 1000, 2000]
+        for n in sizes:
             code = """\
                 data = [
                 """ + "".join("""\
@@ -1383,7 +1384,7 @@ class MiscArcTest(CoverageTest):
                 print(len(data))
                 """
             self.check_coverage(code, arcs=[(-1, 1), (1, 2*n+4), (2*n+4, -1)])
-            assert self.stdout().split()[-1] == str(n)
+        assert self.stdout().split() == [str(n) for n in sizes]
 
     def test_partial_generators(self):
         # https://github.com/nedbat/coveragepy/issues/475
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index a0744452..0eb26cd0 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -545,8 +545,9 @@ class CmdLineTest(BaseCmdLineTest):
         # config file.
         self.command_line("run --concurrency=multiprocessing --branch foo.py", ret=ERR)
         msg = "Options affecting multiprocessing must only be specified in a configuration file."
-        assert msg in self.stderr()
-        assert "Remove --branch from the command line." in self.stderr()
+        _, err = self.stdouterr()
+        assert msg in err
+        assert "Remove --branch from the command line." in err
 
     def test_run_debug(self):
         self.cmd_executes("run --debug=opt1 foo.py", """\
@@ -915,8 +916,9 @@ class CmdMainTest(CoverageTest):
     def test_raise(self):
         ret = coverage.cmdline.main(['raise'])
         assert ret == 1
-        assert self.stdout() == ""
-        err = self.stderr().split('\n')
+        out, err = self.stdouterr()
+        assert out == ""
+        err = err.split('\n')
         assert err[0] == 'Traceback (most recent call last):'
         assert err[-3] == '    raise Exception("oh noes!")'
         assert err[-2] == 'Exception: oh noes!'
diff --git a/tests/test_execfile.py b/tests/test_execfile.py
index db78d0f6..d221f2d3 100644
--- a/tests/test_execfile.py
+++ b/tests/test_execfile.py
@@ -193,33 +193,39 @@ class RunModuleTest(UsingModulesMixin, CoverageTest):
 
     def test_runmod1(self):
         run_python_module(["runmod1", "hello"])
-        assert self.stderr() == ""
-        assert self.stdout() == "runmod1: passed hello\n"
+        out, err = self.stdouterr()
+        assert out == "runmod1: passed hello\n"
+        assert err == ""
 
     def test_runmod2(self):
         run_python_module(["pkg1.runmod2", "hello"])
-        assert self.stderr() == ""
-        assert self.stdout() == "pkg1.__init__: pkg1\nrunmod2: passed hello\n"
+        out, err = self.stdouterr()
+        assert out == "pkg1.__init__: pkg1\nrunmod2: passed hello\n"
+        assert err == ""
 
     def test_runmod3(self):
         run_python_module(["pkg1.sub.runmod3", "hello"])
-        assert self.stderr() == ""
-        assert self.stdout() == "pkg1.__init__: pkg1\nrunmod3: passed hello\n"
+        out, err = self.stdouterr()
+        assert out == "pkg1.__init__: pkg1\nrunmod3: passed hello\n"
+        assert err == ""
 
     def test_pkg1_main(self):
         run_python_module(["pkg1", "hello"])
-        assert self.stderr() == ""
-        assert self.stdout() == "pkg1.__init__: pkg1\npkg1.__main__: passed hello\n"
+        out, err = self.stdouterr()
+        assert out == "pkg1.__init__: pkg1\npkg1.__main__: passed hello\n"
+        assert err == ""
 
     def test_pkg1_sub_main(self):
         run_python_module(["pkg1.sub", "hello"])
-        assert self.stderr() == ""
-        assert self.stdout() == "pkg1.__init__: pkg1\npkg1.sub.__main__: passed hello\n"
+        out, err = self.stdouterr()
+        assert out == "pkg1.__init__: pkg1\npkg1.sub.__main__: passed hello\n"
+        assert err == ""
 
     def test_pkg1_init(self):
         run_python_module(["pkg1.__init__", "wut?"])
-        assert self.stderr() == ""
-        assert self.stdout() == "pkg1.__init__: pkg1\npkg1.__init__: __main__\n"
+        out, err = self.stdouterr()
+        assert out == "pkg1.__init__: pkg1\npkg1.__init__: __main__\n"
+        assert err == ""
 
     def test_no_such_module(self):
         with pytest.raises(NoSource, match="No module named '?i_dont_exist'?"):