feat(core): implement plugin fiber state machine and reactive dependency reconciler

backend/core/fiber_test.go

@@ -0,0 +1,111 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package core_test
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"Wavelet/core"
+)
+
+type MockServiceA interface {
+	DoA() string
+}
+
+type mockServiceAImpl struct{}
+
+func (m *mockServiceAImpl) DoA() string { return "doneA" }
+
+type MockServiceB interface {
+	DoB() string
+}
+
+type mockServiceBImpl struct{}
+
+func (m *mockServiceBImpl) DoB() string { return "doneB" }
+
+type mockProviderPlugin struct {
+	name    string
+	applied bool
+}
+
+func (p *mockProviderPlugin) Name() string {
+	return p.name
+}
+
+func (p *mockProviderPlugin) Apply(ctx *core.Context) error {
+	p.applied = true
+	core.Provide[MockServiceA](ctx, &mockServiceAImpl{})
+	return nil
+}
+
+type mockConsumerPlugin struct {
+	name    string
+	applied bool
+	gotSvc  MockServiceA
+}
+
+func (p *mockConsumerPlugin) Name() string {
+	return p.name
+}
+
+func (p *mockConsumerPlugin) Inject() []reflect.Type {
+	return []reflect.Type{
+		reflect.TypeFor[MockServiceA](),
+	}
+}
+
+func (p *mockConsumerPlugin) Apply(ctx *core.Context) error {
+	p.applied = true
+	svc, err := core.Inject[MockServiceA](ctx)
+	if err != nil {
+		return err
+	}
+	p.gotSvc = svc
+	return nil
+}
+
+func TestFiber_ConfluenceAndReactiveActivation(t *testing.T) {
+	app := core.NewApp()
+
+	// Register Consumer BEFORE Provider to test confluence & out-of-order dependency resolution
+	consumer := &mockConsumerPlugin{name: "consumer-plugin"}
+	provider := &mockProviderPlugin{name: "provider-plugin"}
+
+	app.Use(consumer, provider)
+
+	err := app.Start(context.Background())
+	require.NoError(t, err)
+
+	assert.True(t, provider.applied, "provider should be applied")
+	assert.True(t, consumer.applied, "consumer should be reactively applied once dependency was provided")
+	assert.NotNil(t, consumer.gotSvc)
+	assert.Equal(t, "doneA", consumer.gotSvc.DoA())
+
+	fibers := app.Fibers()
+	require.Equal(t, 2, len(fibers))
+	for _, f := range fibers {
+		assert.Equal(t, core.FiberActive, f.State())
+	}
+
+	err = app.Stop()
+	assert.NoError(t, err)
+}
+
+func TestFiber_UnsatisfiedDependencyReturnsError(t *testing.T) {
+	app := core.NewApp()
+
+	// Register Consumer whose dependency is never provided
+	consumer := &mockConsumerPlugin{name: "consumer-plugin"}
+	app.Use(consumer)
+
+	err := app.Start(context.Background())
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "unsatisfied dependencies")
+}