capture: replace TeeSysCapture with SysCapture(tee=True)

This is more straightforward and does not require duplicating the
initialization logic.

src/_pytest/capture.py

@@ -75,7 +75,9 @@ def _get_multicapture(method: "_CaptureMethod") -> "MultiCapture":
     elif method == "no":
         return MultiCapture(in_=None, out=None, err=None)
     elif method == "tee-sys":
-        return MultiCapture(in_=None, out=TeeSysCapture(1), err=TeeSysCapture(2))
+        return MultiCapture(
+            in_=None, out=SysCapture(1, tee=True), err=SysCapture(2, tee=True)
+        )
     raise ValueError("unknown capturing method: {!r}".format(method))
 
 
@@ -620,7 +622,7 @@ class SysCaptureBinary:
     EMPTY_BUFFER = b""
     _state = None
 
-    def __init__(self, fd, tmpfile=None):
+    def __init__(self, fd, tmpfile=None, *, tee=False):
         name = patchsysdict[fd]
         self._old = getattr(sys, name)
         self.name = name
@@ -628,7 +630,7 @@ class SysCaptureBinary:
             if name == "stdin":
                 tmpfile = DontReadFromInput()
             else:
-                tmpfile = CaptureIO()
+                tmpfile = CaptureIO() if not tee else TeeCaptureIO(self._old)
         self.tmpfile = tmpfile
 
     def __repr__(self):
@@ -684,19 +686,6 @@ class SysCapture(SysCaptureBinary):
         self._old.flush()
 
 
-class TeeSysCapture(SysCapture):
-    def __init__(self, fd, tmpfile=None):
-        name = patchsysdict[fd]
-        self._old = getattr(sys, name)
-        self.name = name
-        if tmpfile is None:
-            if name == "stdin":
-                tmpfile = DontReadFromInput()
-            else:
-                tmpfile = TeeCaptureIO(self._old)
-        self.tmpfile = tmpfile
-
-
 class DontReadFromInput:
     encoding = None
 

testing/test_capture.py

@@ -37,9 +37,9 @@ def StdCapture(out: bool = True, err: bool = True, in_: bool = True) -> MultiCap
 
 def TeeStdCapture(out: bool = True, err: bool = True, in_: bool = True) -> MultiCapture:
     return capture.MultiCapture(
-        in_=capture.TeeSysCapture(0) if in_ else None,
-        out=capture.TeeSysCapture(1) if out else None,
-        err=capture.TeeSysCapture(2) if err else None,
+        in_=capture.SysCapture(0, tee=True) if in_ else None,
+        out=capture.SysCapture(1, tee=True) if out else None,
+        err=capture.SysCapture(2, tee=True) if err else None,
     )
 
 
@@ -1292,8 +1292,10 @@ def test_close_and_capture_again(testdir):
     )
 
 
-@pytest.mark.parametrize("method", ["SysCapture", "FDCapture", "TeeSysCapture"])
-def test_capturing_and_logging_fundamentals(testdir, method):
+@pytest.mark.parametrize(
+    "method", ["SysCapture(2)", "SysCapture(2, tee=True)", "FDCapture(2)"]
+)
+def test_capturing_and_logging_fundamentals(testdir, method: str) -> None:
     # here we check a fundamental feature
     p = testdir.makepyfile(
         """
@@ -1303,7 +1305,7 @@ def test_capturing_and_logging_fundamentals(testdir, method):
         cap = capture.MultiCapture(
             in_=None,
             out=None,
-            err=capture.%s(2),
+            err=capture.%s,
         )
         cap.start_capturing()