Define adapter interfaces and fake implementations

internal/adapters/seriatim/fake.go

@@ -0,0 +1,40 @@
+package seriatim
+
+import "context"
+
+// NoopRunner is a deterministic no-op seriatim adapter.
+type NoopRunner struct{}
+
+// Run returns the requested output path with placeholder metadata.
+func (n *NoopRunner) Run(ctx context.Context, req MergeRequest) (MergeResult, error) {
+	if err := ctx.Err(); err != nil {
+		return MergeResult{}, err
+	}
+	return MergeResult{MergedTranscriptPath: req.OutputMergedTranscriptPath, Metadata: map[string]any{"placeholder": true}}, nil
+}
+
+// FakeRunner captures merge requests and returns deterministic responses.
+type FakeRunner struct {
+	Requests []MergeRequest
+	Err      error
+	Result   MergeResult
+}
+
+// Run records request and returns configured response.
+func (f *FakeRunner) Run(ctx context.Context, req MergeRequest) (MergeResult, error) {
+	if err := ctx.Err(); err != nil {
+		return MergeResult{}, err
+	}
+	f.Requests = append(f.Requests, req)
+	if f.Err != nil {
+		return MergeResult{}, f.Err
+	}
+	res := f.Result
+	if res.MergedTranscriptPath == "" {
+		res.MergedTranscriptPath = req.OutputMergedTranscriptPath
+	}
+	if res.Metadata == nil {
+		res.Metadata = map[string]any{"fake": true}
+	}
+	return res, nil
+}

internal/adapters/seriatim/fake_test.go

@@ -0,0 +1,31 @@
+package seriatim
+
+import (
+	"context"
+	"errors"
+	"testing"
+)
+
+func TestFakeRunnerCapturesRequestAndReturnsPath(t *testing.T) {
+	fake := &FakeRunner{}
+	req := MergeRequest{GeneratedConfigPath: "config/seriatim.yml", OutputMergedTranscriptPath: "transcripts/merged.json"}
+
+	res, err := fake.Run(context.Background(), req)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if len(fake.Requests) != 1 || fake.Requests[0].GeneratedConfigPath == "" {
+		t.Fatalf("requests = %#v, want captured request", fake.Requests)
+	}
+	if res.MergedTranscriptPath != req.OutputMergedTranscriptPath {
+		t.Fatalf("merged path = %q, want %q", res.MergedTranscriptPath, req.OutputMergedTranscriptPath)
+	}
+}
+
+func TestFakeRunnerError(t *testing.T) {
+	fake := &FakeRunner{Err: errors.New("boom")}
+	_, err := fake.Run(context.Background(), MergeRequest{})
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}

internal/adapters/seriatim/runner.go

@@ -3,18 +3,22 @@ package seriatim
 
 import "context"
 
-// Runner is a placeholder adapter interface for seriatim invocation.
+// Runner is the adapter boundary for seriatim merge invocations.
 type Runner interface {
 	Run(ctx context.Context, req MergeRequest) (MergeResult, error)
 }
 
-// MergeRequest is a placeholder merge input.
+// MergeRequest describes a seriatim merge invocation.
 type MergeRequest struct {
-	TranscriptPaths []string
-	OutputPath      string
+	GeneratedConfigPath        string
+	InputTranscriptPaths       []string
+	OutputMergedTranscriptPath string
+	StdoutLogPath              string
+	StderrLogPath              string
 }
 
-// MergeResult is a placeholder merge output.
+// MergeResult describes a merge output.
 type MergeResult struct {
-	MergedPath string
+	MergedTranscriptPath string
+	Metadata             map[string]any
 }