Test the execution example in Go

docs/roadmap/implementation.md

@@ -88,6 +88,10 @@ Validation: format changed Go files and run
 `go test ./examples/go-library/run`. Confirm the test executes the workflow,
 not just the summary type. These expected values describe this fixture only.
 
+Completion: extracted the execution workflow and JSON encoding into a helper
+with explicit context, resource directory, and writer. The focused Go test
+executes the workflow and checks its summary; it passed on Go 1.27.0.
+
 ## Stage 2: Test Preparation With Explicit Resource Context
 
 Scope: `examples/go-library/prepare/main.go` and its new `main_test.go`.

examples/go-library/run/main.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"os"
+	"path/filepath"
 
 	"go.maximumdirect.net/configkit"
 	"go.maximumdirect.net/promptkit"
@@ -39,41 +41,41 @@ type summary struct {
 }
 
 func main() {
+	if err := run(context.Background(), "examples/go-library/run", os.Stdout); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func run(ctx context.Context, exampleDir string, out io.Writer) error {
 	endpoint, model := "https://example.invalid/v1", "offline-model"
 	engine, err := promptkit.NewEngine(promptkit.Config{Sources: promptkit.ConfigurationSources{
 		Underlays: []configkit.Underlay{{Inputs: []configkit.Input{{Source: promptkit.ProfileSource("example profile", []promptkit.ProfileConfig{
 			{ID: "offline-example", Endpoint: &endpoint, Model: &model},
 		})}}}},
-		Main: &configkit.Input{Source: configkit.File("examples/go-library/run/prompt.yaml")},
+		Main: &configkit.Input{Source: configkit.File(filepath.Join(exampleDir, "prompt.yaml"))},
 	}}, promptkit.WithLLMClient(deterministicClient{}))
 	if err != nil {
-		exit(err)
+		return err
 	}
 
-	result, err := engine.Run(context.Background(), promptkit.RunRequest{
+	result, err := engine.Run(ctx, promptkit.RunRequest{
 		PromptID: "example.run",
 		Inputs: map[string]promptkit.ArtifactRef{
 			"note": promptkit.Inline("Ada finished the migration review."),
 		},
 	})
 	if err != nil {
-		exit(err)
+		return err
 	}
 
-	encoder := json.NewEncoder(os.Stdout)
+	encoder := json.NewEncoder(out)
 	encoder.SetIndent("", "  ")
-	if err := encoder.Encode(summary{
+	return encoder.Encode(summary{
 		Output:           result.RawOutput,
 		ValidationStatus: result.Validation.Status,
 		IsValid:          result.Validation.IsValid,
 		Model:            result.ModelName,
 		TotalTokens:      result.Usage.TotalTokens,
-	}); err != nil {
-		exit(err)
-	}
-}
-
-func exit(err error) {
-	fmt.Fprintln(os.Stderr, err)
-	os.Exit(1)
+	})
 }

examples/go-library/run/main_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+)
+
+func TestRunExample(t *testing.T) {
+	var output bytes.Buffer
+	if err := run(t.Context(), ".", &output); err != nil {
+		t.Fatal(err)
+	}
+	var got struct {
+		Output string `json:"output"`
+		Valid  *bool  `json:"is_valid"`
+		Status string `json:"validation_status"`
+		Model  string `json:"model"`
+		Tokens *int   `json:"total_tokens"`
+	}
+	if err := json.Unmarshal(output.Bytes(), &got); err != nil {
+		t.Fatal(err)
+	}
+	if got.Output != "Ada finished the migration review." || got.Valid == nil || !*got.Valid ||
+		got.Status != "passed" || got.Model != "offline-model" || got.Tokens == nil || *got.Tokens != 18 {
+		t.Fatalf("unexpected execution summary: %+v", got)
+	}
+}