Very scary test here. Trying to see if we can boost speed on very large terminals.

tests/unit/test_vcsa_driver.py

@@ -22,14 +22,49 @@ class BulkReadFailure:
         return next(self.chunks)
 
 
-def test_vcsa_read_fallback_stops_at_eof():
+class TransientInvalidArgumentRead:
+    def __init__(self, payload):
+        self.payload = payload
+        self.read_calls = 0
+        self.readline_calls = 0
+
+    def seek(self, offset):
+        assert offset == 0
+
+    def read(self):
+        self.read_calls += 1
+        if self.read_calls == 1:
+            raise OSError(22, "Invalid argument")
+        return self.payload
+
+    def readline(self, size):
+        self.readline_calls += 1
+        return b""
+
+
+def build_vcsa_driver():
     vcsa_driver = VcsaDriver.__new__(VcsaDriver)
     vcsa_driver.env = {
         "runtime": {
             "DebugManager": Mock(),
         }
     }
+    vcsa_driver.read_retry_delay = 0
+    return vcsa_driver
+
+
+def test_vcsa_read_fallback_stops_at_eof():
+    vcsa_driver = build_vcsa_driver()
     screen_file = BulkReadFailure([b"a", b"b", b""])
 
     assert vcsa_driver.read_file(screen_file) == b"ab"
     assert screen_file.readline_calls == 3
+
+
+def test_vcsa_read_retries_transient_invalid_argument():
+    vcsa_driver = build_vcsa_driver()
+    screen_file = TransientInvalidArgumentRead(b"\x01\x02\x00\x00x")
+
+    assert vcsa_driver.read_file(screen_file) == b"\x01\x02\x00\x00x"
+    assert screen_file.read_calls == 2
+    assert screen_file.readline_calls == 0