tests: add test for preserving newlines with capsys/capfd

Ref: pytest-dev#7517

testing/test_capture.py

@@ -526,6 +526,14 @@ def test_hello(capfd):
         )
         reprec.assertoutcome(passed=1)
 
+    @pytest.mark.parametrize("fixturename", ("capfd", "capsys"))
+    @pytest.mark.parametrize("nl", ("\n", "\r\n", "\r"))
+    def test_preserves_newlines(self, fixturename, nl, request):
+        fixture = request.getfixturevalue(fixturename)
+        print("test", end=nl)
+        out, err = fixture.readouterr()
+        assert out == "test" + nl
+
     @needsosdup
     def test_capfdbinary(self, testdir):
         reprec = testdir.inline_runsource(