Split the code into library and application

slackbuilder.cabal

@@ -19,18 +19,11 @@ common dependencies
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -Wall
   build-depends:
     base ^>= 4.16.4.0,
-
-executable slackbuilder
-  import: dependencies
-  main-is: Main.hs
-
-  other-modules:
-    SlackBuilder.CommandLine
-    SlackBuilder.Config
-    SlackBuilder.Download
-    SlackBuilder.Package
-    SlackBuilder.Trans
-    SlackBuilder.Updater
+    cryptonite >= 0.30,
+    filepath ^>= 1.4.2,
+    modern-uri ^>= 0.3.6,
+    text ^>= 2.0
+  default-language: Haskell2010
   default-extensions:
     DataKinds
     DuplicateRecordFields
@@ -41,25 +34,38 @@ executable slackbuilder
     QuasiQuotes
     TemplateHaskell
     TypeApplications
+
+library slackbuilder-internal
+  import: dependencies
+  exposed-modules:
+    SlackBuilder.Config
+    SlackBuilder.Package
+    SlackBuilder.Trans
+  hs-source-dirs: lib
+  build-depends:
+    exceptions >= 0.10,
+    tomland ^>= 1.3.3,
+    transformers ^>= 0.5.6
+
+executable slackbuilder
+  import: dependencies
+  main-is: Main.hs
+
+  other-modules:
+    SlackBuilder.CommandLine
+    SlackBuilder.Download
+    SlackBuilder.Updater
   build-depends:
     aeson ^>= 2.2.0,
     bytestring ^>= 0.11.0,
     conduit ^>= 1.3.5,
-    cryptonite >= 0.30,
-    exceptions >= 0.10,
-    filepath ^>= 1.4.2,
     http-client ^>= 0.7,
-    modern-uri ^>= 0.3.6,
     optparse-applicative ^>= 0.18.1,
     process ^>= 1.6.17,
     req ^>= 3.13,
-    text ^>= 2.0,
-    tomland ^>= 1.3.3,
-    transformers ^>= 0.5.6,
     unordered-containers ^>= 0.2.19,
     vector ^>= 0.13.0
   hs-source-dirs: app
-  default-language: Haskell2010
 
 test-suite slackbuilder-test
   import: dependencies
@@ -68,8 +74,7 @@ test-suite slackbuilder-test
 
   other-modules:
     SlackBuilder.PackageSpec
-  hs-source-dirs:
-    tests
-  default-language: Haskell2010
+  hs-source-dirs: tests
   build-depends:
-    hspec >= 2.10.9 && < 2.12
+    hspec >= 2.10.9 && < 2.12,
+    slackbuilder-internal

tests/SlackBuilder/PackageSpec.hs

@@ -2,7 +2,17 @@ module SlackBuilder.PackageSpec
     ( spec
     ) where 
 
-import Test.Hspec (Spec)
+import SlackBuilder.Package
+import Test.Hspec (Spec, describe, it, shouldBe)
+import Text.URI.QQ (uri)
 
 spec :: Spec
-spec = pure ()
+spec = do
+    describe "renderDownloadWithVersion" $
+        it "renders text as URL" $
+            let given = DownloadTemplate
+                    $ pure
+                    $ StaticPlaceholder "https://example.com"
+                actual = renderDownloadWithVersion given "1.2"
+                expected = Just [uri|https://example.com|]
+             in actual `shouldBe` expected