Add __repr__ for RunResult

src/_pytest/pytester.py

@@ -398,6 +398,12 @@ def __init__(self, ret, outlines, errlines, duration):
         self.stderr = LineMatcher(errlines)
         self.duration = duration
 
+    def __repr__(self):
+        return (
+            "<RunResult ret=%r len(stdout.lines)=%d len(stderr.lines)=%d duration=%.2fs>"
+            % (self.ret, len(self.stdout.lines), len(self.stderr.lines), self.duration)
+        )
+
     def parseoutcomes(self):
         """Return a dictionary of outcomestring->num from parsing the terminal
         output that the test process produced.

testing/test_pytester.py

@@ -127,6 +127,17 @@ def test_potato():
     assert result.ret == 0
 
 
+def test_runresult_repr():
+    from _pytest.pytester import RunResult
+
+    assert (
+        repr(
+            RunResult(ret="ret", outlines=[""], errlines=["some", "errors"], duration=1)
+        )
+        == "<RunResult ret='ret' len(stdout.lines)=1 len(stderr.lines)=2 duration=1.00s>"
+    )
+
+
 def test_xpassed_with_strict_is_considered_a_failure(testdir):
     testdir.makepyfile(
         """