test: Add tests for using build.context

These are simple tests to make sure that the generated docker-compose.json
looks like it should. This means has a build.context and does NOT
have an image defined - the image is built when starting the service.

src/haskell/test/Arion/NixSpec.hs

@@ -13,19 +13,34 @@ import qualified Data.Text                     as T
 import qualified Data.Text.IO                  as T
 
 spec :: Spec
-spec = describe "evaluateComposition" $ it "matches an example" $ do
-  x <- Arion.Nix.evaluateComposition EvaluationArgs
-    { evalUid      = 123
-    , evalModules  = NEL.fromList
-                       ["src/haskell/testdata/Arion/NixSpec/arion-compose.nix"]
-    , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
-    , evalWorkDir  = Nothing
-    , evalMode     = ReadOnly
-    , evalUserArgs = ["--show-trace"]
-    }
-  let actual = pretty x
-  expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-compose.json"
-  censorPaths actual `shouldBe` censorPaths expected
+spec = describe "evaluateComposition" $ do
+  it "matches an example" $ do
+    x <- Arion.Nix.evaluateComposition EvaluationArgs
+      { evalUid      = 123
+      , evalModules  = NEL.fromList
+                         ["src/haskell/testdata/Arion/NixSpec/arion-compose.nix"]
+      , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
+      , evalWorkDir  = Nothing
+      , evalMode     = ReadOnly
+      , evalUserArgs = ["--show-trace"]
+      }
+    let actual = pretty x
+    expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-compose.json"
+    censorPaths actual `shouldBe` censorPaths expected
+
+  it "matches an build.context example" $ do
+    x <- Arion.Nix.evaluateComposition EvaluationArgs
+      { evalUid      = 1234
+      , evalModules  = NEL.fromList
+                         ["src/haskell/testdata/Arion/NixSpec/arion-context-compose.nix"]
+      , evalPkgs     = "import <nixpkgs> { system = \"x86_64-linux\"; }"
+      , evalWorkDir  = Nothing
+      , evalMode     = ReadOnly
+      , evalUserArgs = ["--show-trace"]
+      }
+    let actual = pretty x
+    expected <- T.readFile "src/haskell/testdata/Arion/NixSpec/arion-context-compose.json"
+    censorPaths actual `shouldBe` censorPaths expected
 
 censorPaths :: Text -> Text
 censorPaths = censorImages . censorStorePaths

src/haskell/test/Spec.hs

@@ -9,3 +9,4 @@ import qualified Arion.NixSpec
 spec :: Spec
 spec = do
   describe "Arion.Nix" Arion.NixSpec.spec
+

src/haskell/testdata/Arion/NixSpec/arion-context-compose.json

@@ -0,0 +1,41 @@
+{
+    "networks": {
+        "default": {
+            "name": "unit-test-data"
+        }
+    },
+    "services": {
+        "webserver": {
+            "build": {
+                "context": "<STOREPATH>"
+            },
+            "environment": {},
+            "ports": [
+                "8080:80"
+            ],
+            "sysctls": {},
+            "volumes": []
+        }
+    },
+    "version": "3.4",
+    "volumes": {},
+    "x-arion": {
+        "images": [
+            {
+                "imageExe": "<STOREPATH>",
+                "imageName": "localhost/webserver",
+                "imageTag": "<HASH>"
+            }
+        ],
+        "project": {
+            "name": "unit-test-data"
+        },
+        "serviceInfo": {
+            "webserver": {
+                "defaultExec": [
+                    "/bin/sh"
+                ]
+            }
+        }
+    }
+}

src/haskell/testdata/Arion/NixSpec/arion-context-compose.nix

@@ -0,0 +1,9 @@
+{
+  project.name = "unit-test-data";
+  services.webserver.service = {
+    build.context = "${./build-context}";
+    ports = [
+      "8080:80"
+    ];
+  };
+}

src/haskell/testdata/Arion/NixSpec/build-context/Dockerfile

@@ -0,0 +1,4 @@
+FROM nginx
+
+RUN echo this is a dockerfile to be built
+