Add new shelltestrunner based test-suite

ghc-mod.cabal

@@ -299,6 +299,20 @@ Test-Suite spec
   Build-Depends:        hspec             < 2.4  && >= 2.0.0
   X-Build-Depends-Like: CLibName
 
+
+Test-Suite shelltest
+  Default-Language:     Haskell2010
+  Main-Is:              ShellTest.hs
+  Hs-Source-Dirs:       shelltest
+  Type:                 exitcode-stdio-1.0
+  Build-Tools:          shelltest
+  Build-Depends:        base
+                      , process           < 1.5
+                      -- , shelltestrunner >= 1.3.5
+  if !flag(shelltest)
+    Buildable: False
+
+
 Benchmark criterion
   Type:                 exitcode-stdio-1.0
   Default-Language:     Haskell2010
@@ -325,6 +339,13 @@ Benchmark criterion
 
                       , ghc-mod
 
+
+Flag shelltest
+  Description: Enable/disable shelltest test-suite
+  Default: False
+  Manual:  True
+
+
 Source-Repository head
   Type:                 git
   Location:             https://github.com/DanielG/ghc-mod.git