For some reason we started getting:

cabal: Cannot test the package linear-base-0.1.1 because none of the
components are available to build: the test suite 'test' and the test suite
'examples' are not available because the solver did not find a plan that
included the test suites. Force the solver to enable this for all packages by
adding the line 'tests: True' to the 'cabal.project.local' file.

On the CI, even on our branches without any build system related changes. It's not clear to my why is this happening, but the only mutable thing I can think of is the Hackage index, so probably a version of a package is released and that is confusing cabal.

Anyhow, adding tests: true to cabal.project as suggested seems to fix the issue. I added it to cabal.project instead of cabal.project.local because I don't see why anyone developing linear-base wouldn't want the tests.

Alternatives I can think of:

• We can leave cabal.project as is, and pass --enable-test to cabal invocations which does the same thing.
• We can figure out why the solver is not able to figure things out and try to fix that with adding version bounds; but it's not clear to me if this is better or how to do this.