chore: Add tests and fix merging environment, not replacing it

fixtures/environment/smoke.yaml

@@ -0,0 +1,38 @@
+tests:
+  - name: environment
+    environment:
+      TEST_ENV: "test-value"
+    command: |
+      echo $TEST_ENV
+    stdout: |
+      test-value
+
+  - name: inherits
+    command: |
+      echo $ONLY_DEFINED_IN_SPEC
+    stdout: |
+      defined_in_spec
+
+  - name: overwrites
+    environment:
+      OVERWRITE_IN_FIXTURE: "overwritten"
+    command: |
+      echo $OVERWRITE_IN_FIXTURE
+    stdout: |
+      overwritten
+
+  - name: not-defined
+    command: |
+      echo $NOT_DEFINED
+    stdout: "\n"
+
+  - name: spec-is-merged-into-fixture-not-replaced
+    environment:
+      OVERWRITE_IN_FIXTURE: "overwritten"
+    command: |
+      echo $OVERWRITE_IN_FIXTURE
+      echo $ONLY_DEFINED_IN_SPEC
+    stdout: |
+      overwritten
+      defined_in_spec
+      

spec/environment.yaml

@@ -1,8 +1,10 @@
 tests:
-  - name: shell
+  - name: environment
+    args:
+      - fixtures/environment/smoke.yaml
+    exit-code: 0
     environment:
-      TEST_ENV: "test-value"
-    command: |
-      echo $TEST_ENV
-    stdout: |
-      test-value
+      OVERWRITE_IN_FIXTURE: "not_overwritten"
+      ONLY_DEFINED_IN_SPEC: "defined_in_spec"
+    stdout:
+      - file: io/environment.out

spec/io/environment.out

@@ -0,0 +1,12 @@
+environment
+  succeeded
+inherits
+  succeeded
+overwrites
+  succeeded
+not-defined
+  succeeded
+spec-is-merged-into-fixture-not-replaced
+  succeeded
+
+5 tests, 0 failures

src/lib/Test/Smoke/Executable.hs

@@ -5,6 +5,7 @@ import Data.Map.Strict qualified as Map
 import Data.Text (Text)
 import Data.Text.IO qualified as Text.IO
 import Data.Vector qualified as Vector
+import System.Environment (getEnvironment)
 import System.Exit (ExitCode)
 import System.IO (hClose)
 import System.IO.Temp (withSystemTempFile)
@@ -21,17 +22,23 @@ runExecutable ::
   Maybe EnvVars ->
   Maybe WorkingDirectory ->
   IO (ExitCode, Text, Text)
-runExecutable (ExecutableProgram executablePath executableArgs) args (StdIn stdIn) env workingDirectory =
+runExecutable (ExecutableProgram executablePath executableArgs) args (StdIn stdIn) env workingDirectory = do
+  mergedEnv <- traverse addOriginalEnv env
   readCreateProcessWithExitCode
     ( ( proc
           (toFilePath executablePath)
           (Vector.toList (unArgs (executableArgs <> args)))
       )
         { cwd = toFilePath . unWorkingDirectory <$> workingDirectory,
-          env = Map.toList . unEnvVars <$> env
+          env = Map.toList . unEnvVars <$> mergedEnv
         }
     )
     stdIn
+  where
+    addOriginalEnv :: EnvVars -> IO EnvVars
+    addOriginalEnv overriddenEnv = do
+      originalEnv <- EnvVars . Map.fromList <$> getEnvironment
+      pure $ overriddenEnv <> originalEnv
 runExecutable (ExecutableScript (Shell shellPath shellArgs) (Script script)) args stdIn env workingDirectory =
   withSystemTempFile defaultShellScriptName $ \scriptPath scriptHandle -> do
     Text.IO.hPutStr scriptHandle script

src/lib/Test/Smoke/Types/Base.hs

@@ -59,7 +59,7 @@ instance FromFixture Args where
 newtype EnvVars = EnvVars
   { unEnvVars :: Map String String
   }
-  deriving (FromJSON)
+  deriving (Semigroup, FromJSON)
 
 newtype Script = Script
   { unScript :: Text