feat(module): add four-phase Module interface and registry

internal/module/registry_test.go

@@ -0,0 +1,57 @@
+package module
+
+import (
+	"context"
+	"testing"
+)
+
+type fakeModule struct{ id string; deps []string }
+
+func (f fakeModule) Meta() Meta { return Meta{ID: f.id, Name: f.id, Deps: f.deps} }
+func (f fakeModule) Detect(context.Context) (State, error)              { return nil, nil }
+func (f fakeModule) Plan(context.Context, State) (Plan, error)          { return Plan{}, nil }
+func (f fakeModule) Apply(context.Context, Plan, Reporter) error        { return nil }
+func (f fakeModule) Verify(context.Context) error                       { return nil }
+
+func TestRegistry(t *testing.T) {
+	t.Run("register then get", func(t *testing.T) {
+		r := NewRegistry()
+		if err := r.Register(fakeModule{id: "a"}); err != nil {
+			t.Fatal(err)
+		}
+		m, ok := r.Get("a")
+		if !ok || m.Meta().ID != "a" {
+			t.Fatalf("want module a, got %v ok=%v", m, ok)
+		}
+	})
+
+	t.Run("duplicate register errors", func(t *testing.T) {
+		r := NewRegistry()
+		_ = r.Register(fakeModule{id: "a"})
+		if err := r.Register(fakeModule{id: "a"}); err == nil {
+			t.Fatal("expected duplicate error")
+		}
+	})
+
+	t.Run("empty id errors", func(t *testing.T) {
+		r := NewRegistry()
+		if err := r.Register(fakeModule{id: ""}); err == nil {
+			t.Fatal("expected empty-id error")
+		}
+	})
+
+	t.Run("all is sorted by id", func(t *testing.T) {
+		r := NewRegistry()
+		_ = r.Register(fakeModule{id: "b"})
+		_ = r.Register(fakeModule{id: "a"})
+		_ = r.Register(fakeModule{id: "c"})
+		all := r.All()
+		got := []string{all[0].Meta().ID, all[1].Meta().ID, all[2].Meta().ID}
+		want := []string{"a", "b", "c"}
+		for i := range got {
+			if got[i] != want[i] {
+				t.Fatalf("All() = %v, want %v", got, want)
+			}
+		}
+	})
+}