Cannot configure cabal package to enable tests [on hold]

If I try to enable tests by running cabal configure --enable-tests for my package, it fails with the following error message: rejecting: mypackage-0.1.2.0:!test (constraint from config file, command line flag, or user target requires opposite flag selection) trying: mypackage-0.1.2.0:*test next goal: myotherpackage (dependency of mypackage-0.1.2.0:*test) Dependency tree exhaustively searched.

What does to !test and *test suffixes mean in the package id?

BTW, all dependencies of mypackage are already installed. Cabal check reports OK.

Edit:

mypackage.cabal is:

name:                mypackage
version:             0.1.2.0
build-type:          Simple
cabal-version:       >=1.10

test-suite mypackage-test
  type:                exitcode-stdio-1.0
  hs-source-dirs:      .
  main-is:             Main.hs
  build-depends:       base                      >=4.9   && <5.0
                     , myotherpackage >=0.1.2 && <2.0
  default-language:    Haskell2010

while otherpackage.cabal is:

name:                myotherpackage
version:             0.1.2.0
build-type:          Simple
cabal-version:       >=1.10

library
  exposed-modules:              
  other-modules:       

  build-depends:       base              >=4.9 && <5.0
  default-language:    Haskell2010