Add domain types and validation

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/domain/domain_test.go

@@ -0,0 +1,69 @@
+package domain
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestNewManualRejectsEmptyNextAction(t *testing.T) {
+	_, err := NewManual("", "tests pass", 25*time.Minute)
+	if err != ErrMissingNextAction {
+		t.Fatalf("want ErrMissingNextAction, got %v", err)
+	}
+}
+
+func TestNewManualRejectsEmptySuccessCondition(t *testing.T) {
+	_, err := NewManual("Refactor state", "  ", 25*time.Minute)
+	if err != ErrMissingSuccessCondition {
+		t.Fatalf("want ErrMissingSuccessCondition, got %v", err)
+	}
+}
+
+func TestNewManualRejectsZeroTimebox(t *testing.T) {
+	_, err := NewManual("Refactor state", "tests pass", 0)
+	if err != ErrMissingTimebox {
+		t.Fatalf("want ErrMissingTimebox, got %v", err)
+	}
+}
+
+func TestNewManualPopulatesDraftCommitment(t *testing.T) {
+	c, err := NewManual("  Port domain  ", "domain tests pass", 25*time.Minute)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c.NextAction != "Port domain" {
+		t.Errorf("next action not trimmed: %q", c.NextAction)
+	}
+	if c.SuccessCondition != "domain tests pass" {
+		t.Errorf("success condition wrong: %q", c.SuccessCondition)
+	}
+	if c.TimeboxSecs != 1500 {
+		t.Errorf("timebox secs wrong: %d", c.TimeboxSecs)
+	}
+	if c.State != CommitmentDraft {
+		t.Errorf("state should be draft, got %s", c.State)
+	}
+	if c.Source != SourceManual {
+		t.Errorf("source should be manual, got %s", c.Source)
+	}
+	if !strings.HasPrefix(c.ID, "commitment-") {
+		t.Errorf("id should be prefixed, got %s", c.ID)
+	}
+}
+
+func TestCommitmentSerializesSnakeCaseEnums(t *testing.T) {
+	c, _ := NewManual("Port domain", "domain tests pass", 25*time.Minute)
+	data, err := json.Marshal(c)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+	s := string(data)
+	if !strings.Contains(s, `"source":"manual"`) {
+		t.Errorf("missing snake_case source in %s", s)
+	}
+	if !strings.Contains(s, `"state":"draft"`) {
+		t.Errorf("missing snake_case state in %s", s)
+	}
+}