tests: add test_via_exec

Via https://github.com/pytest-dev/pytest/issues/6574.

testing/test_terminal.py

@@ -13,6 +13,7 @@ import py
 
 import pytest
 from _pytest.main import ExitCode
+from _pytest.pytester import Testdir
 from _pytest.reports import BaseReport
 from _pytest.terminal import _folded_skips
 from _pytest.terminal import _get_line_with_reprcrash_message
@@ -1923,3 +1924,11 @@ def test_collecterror(testdir):
             "*= 1 error in *",
         ]
     )
+
+
+def test_via_exec(testdir: Testdir) -> None:
+    p1 = testdir.makepyfile("exec('def test_via_exec(): pass')")
+    result = testdir.runpytest(str(p1), "-vv")
+    result.stdout.fnmatch_lines(
+        ["test_via_exec.py::test_via_exec <- <string> PASSED*", "*= 1 passed in *"]
+    )