test(01-02): add failing test for optional plugin services

- Cover typed Publish/Lookup, duplicate providers and HasPlugin
- Require missing/cycle errors to name plugin IDs before Boot
- Assert greeter works with and without an optional extra

backpack/services_test.go

@@ -0,0 +1,72 @@
+package backpack
+
+import (
+	"testing"
+
+	"git.golem15.com/golem15/summercms/compass"
+)
+
+type ping interface {
+	Ping() string
+}
+
+type pingImpl struct{ s string }
+
+func (p pingImpl) Ping() string { return p.s }
+
+func TestPublishLookup(t *testing.T) {
+	app := New(&compass.Config{})
+	if err := app.Publish[ping](pingImpl{s: "pong"}); err != nil {
+		t.Fatalf("Publish: %v", err)
+	}
+	got, ok := app.Lookup[ping]()
+	if !ok {
+		t.Fatal("Lookup returned false")
+	}
+	if got.Ping() != "pong" {
+		t.Fatalf("Ping = %q, want pong", got.Ping())
+	}
+}
+
+func TestLookupAbsentInterface(t *testing.T) {
+	app := New(&compass.Config{})
+	got, ok := app.Lookup[ping]()
+	if ok {
+		t.Fatalf("Lookup = (%v, true), want false", got)
+	}
+	if got != nil {
+		t.Fatalf("absent lookup value = %v, want nil", got)
+	}
+}
+
+func TestPublishDuplicateRejected(t *testing.T) {
+	app := New(&compass.Config{})
+	if err := app.Publish[ping](pingImpl{s: "a"}); err != nil {
+		t.Fatalf("Publish: %v", err)
+	}
+	if err := app.Publish[ping](pingImpl{s: "b"}); err == nil {
+		t.Fatal("expected duplicate publish error")
+	}
+}
+
+func TestServiceRegistriesAreAppScoped(t *testing.T) {
+	a := New(&compass.Config{})
+	b := New(&compass.Config{})
+	if err := a.Publish[ping](pingImpl{s: "a"}); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := b.Lookup[ping](); ok {
+		t.Fatal("app B should not see app A's service")
+	}
+}
+
+func TestHasPluginUsesCompleteSet(t *testing.T) {
+	app := New(&compass.Config{})
+	app.SetPlugins([]string{"golem15.hello", "golem15.optional"})
+	if !app.HasPlugin("golem15.optional") {
+		t.Fatal("HasPlugin(golem15.optional) = false")
+	}
+	if app.HasPlugin("golem15.missing") {
+		t.Fatal("HasPlugin(golem15.missing) = true")
+	}
+}