Improve test_solvers_archspec_with_virtual_package test

Author: chrisburr

tests/test_solvers.py

@@ -169,6 +169,13 @@ def test_solvers_nvcc_with_virtual_package(solver_factory):
 def test_solvers_archspec_with_virtual_package(solver_factory):
     with suppress_output():
         virtual_packages = virtual_package_repodata()
+
+        # Not having the fake virtual packages should fail
+        solver = solver_factory(("conda-forge", "defaults"), "linux-64")
+        out = solver.solve(["pythia8 8.312"])
+        assert not out[0], out[1]
+
+        # Including the fake virtual packages should succeed
         solver = solver_factory(
             (virtual_packages, "conda-forge", "defaults"), "linux-64"
         )