one more test

Author: nedbat

tests/test_process.py

@@ -1142,6 +1142,13 @@ def test_core_request_sysmon(self) -> None:
             assert core in ("core: CTracer", "core: PyTracer")
             assert warns
 
+    def test_core_request_nonsense(self) -> None:
+        self.del_environ("COVERAGE_TEST_CORES")
+        self.set_environ("COVERAGE_CORE", "nosuchcore")
+        self.make_file("numbers.py", "print(123, 456)")
+        out = self.run_command("coverage run numbers.py")
+        assert "Unknown core value: 'nosuchcore'\n" in out
+
 
 class FailUnderNoFilesTest(CoverageTest):
     """Test that nothing to report results in an error exit status."""