feat: 实现 Instance Ready 领域判定与恢复规则

internal/database/domain/instance/instance.go

@@ -38,22 +38,22 @@ const (
 )
 
 // Snapshot contains persisted observations only, without credentials or live evidence.
-// Failure detail mapping will be added with capability assessment, not intent transitions.
 type Snapshot struct {
 	Phase            Phase
 	ObservedRevision int64
 	Readiness        Readiness
 	ReportedVersion  string
+	Failure          Failure
 }
 
 // Instance protects registration state and pure lifecycle transitions.
 // Reconstitution does not establish live capability evidence, even for a Ready snapshot.
-// This initial slice deliberately exposes no operation that authorizes provisioning.
 type Instance struct {
 	target     ObservationTarget
 	snapshot   Snapshot
 	deleting   bool
 	extensions ExtensionSupport
+	evidence   *CapabilityObservation
 }
 
 func Reconstitute(target ObservationTarget, snapshot Snapshot, deleting bool) (*Instance, error) {
@@ -85,6 +85,8 @@ func (i *Instance) BeginValidation() error {
 	i.snapshot.Phase = PhaseValidating
 	i.snapshot.Readiness = Unknown
 	i.extensions = ExtensionSupport{}
+	i.evidence = nil
+	i.snapshot.Failure = NoFailure
 	return nil
 }
 
@@ -100,6 +102,8 @@ func (i *Instance) BeginDeletion() error {
 	i.snapshot.Phase = PhaseDeleting
 	i.snapshot.Readiness = Unknown
 	i.extensions = ExtensionSupport{}
+	i.evidence = nil
+	i.snapshot.Failure = NoFailure
 	return nil
 }
 

internal/database/domain/instance/readiness.go

@@ -0,0 +1,263 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import "errors"
+
+// Failure 只表示安全类别；驱动错误、凭据和 Condition 文案留在应用边界。
+type Failure uint8
+
+const (
+	NoFailure Failure = iota
+	ObservationIncomplete
+	DependencyUnavailable
+	AuthenticationFailed
+	InsufficientPrivileges
+	RegistryIncompatible
+	RegistryNotUsable
+)
+
+// CheckResult 的零值表示未观察，不能视为成功。
+type CheckResult uint8
+
+const (
+	CheckUnobserved CheckResult = iota
+	CheckPassed
+	CheckUnavailable
+	CheckAuthenticationFailed
+	CheckInsufficientPrivileges
+)
+
+// ManagementChecks 分别记录所需能力；SQL 探测和同轮次关联由 adapter/application 保证。
+// Extensions 不代表任意扩展均可安装；具体请求仍需支持检查、执行及回读。
+type ManagementChecks struct {
+	Connection CheckResult
+	Metadata   CheckResult
+	Roles      CheckResult
+	Databases  CheckResult
+	Grants     CheckResult
+	Extensions CheckResult
+}
+
+func (c ManagementChecks) failure() Failure {
+	for _, check := range []CheckResult{c.Connection, c.Metadata, c.Roles, c.Databases, c.Grants, c.Extensions} {
+		switch check {
+		case CheckPassed:
+		case CheckUnavailable:
+			return DependencyUnavailable
+		case CheckAuthenticationFailed:
+			return AuthenticationFailed
+		case CheckInsufficientPrivileges:
+			return InsufficientPrivileges
+		default:
+			return ObservationIncomplete
+		}
+	}
+	return NoFailure
+}
+
+type RegistryState uint8
+
+const (
+	RegistryUnobserved RegistryState = iota
+	RegistryAbsent
+	RegistryNeedsMigration
+	RegistryUsable
+	RegistryUnsupported
+	RegistryUnavailable
+)
+
+// CapabilityObservation 是值对象，不包含连接、凭据或可变集合。
+type CapabilityObservation struct {
+	target   ObservationTarget
+	version  string
+	checks   ManagementChecks
+	registry RegistryState
+}
+
+func NewCapabilityObservation(target ObservationTarget, version string,
+	checks ManagementChecks, registry RegistryState,
+) (CapabilityObservation, error) {
+	if err := target.Validate(); err != nil {
+		return CapabilityObservation{}, err
+	}
+	return CapabilityObservation{target: target, version: version, checks: checks, registry: registry}, nil
+}
+
+func (o CapabilityObservation) managementFailure() Failure {
+	if failure := o.checks.failure(); failure != NoFailure {
+		return failure
+	}
+	if o.version == "" {
+		return ObservationIncomplete
+	}
+	return NoFailure
+}
+
+func (o CapabilityObservation) registryFailure() Failure {
+	switch o.registry {
+	case RegistryUsable:
+		return NoFailure
+	case RegistryAbsent, RegistryNeedsMigration:
+		return RegistryNotUsable
+	case RegistryUnsupported:
+		return RegistryIncompatible
+	case RegistryUnavailable:
+		return DependencyUnavailable
+	default:
+		return ObservationIncomplete
+	}
+}
+
+type PreparationDecision uint8
+
+const (
+	PreparationDenied PreparationDecision = iota
+	PreparationAllowed
+	AlreadyUsable
+)
+
+func (i *Instance) acceptObservation(o CapabilityObservation, phase Phase) error {
+	if !i.target.Matches(o.target) {
+		return errors.New("capability observation target does not match instance")
+	}
+	if i.deleting || i.snapshot.Phase != phase {
+		return errors.New("capability observation is not allowed in current lifecycle")
+	}
+	return nil
+}
+
+func (i *Instance) fail(failure Failure) {
+	i.evidence = nil
+	i.extensions = ExtensionSupport{}
+	i.snapshot.Readiness = NotReady
+	i.snapshot.Failure = failure
+	i.snapshot.ObservedRevision = i.target.Revision().Value()
+}
+
+// AssessManagement 只推进意图，不执行 registry 写入，也不完成 observedRevision。
+func (i *Instance) AssessManagement(o CapabilityObservation) error {
+	if err := i.acceptObservation(o, PhaseValidating); err != nil {
+		return err
+	}
+	if failure := o.managementFailure(); failure != NoFailure {
+		i.fail(failure)
+		return nil
+	}
+	if failure := o.registryFailure(); failure != NoFailure && failure != RegistryNotUsable {
+		i.fail(failure)
+		return nil
+	}
+	i.snapshot.Phase = PhaseInitializingRegistry
+	i.snapshot.Readiness = Unknown
+	i.snapshot.Failure = NoFailure
+	i.evidence = nil
+	return nil
+}
+
+// PlanRegistryPreparation 不证明 checkpoint 已落盘；应用层必须先保存意图再执行写入。
+func (i *Instance) PlanRegistryPreparation(o CapabilityObservation) (PreparationDecision, error) {
+	if err := i.acceptObservation(o, PhaseInitializingRegistry); err != nil {
+		return PreparationDenied, err
+	}
+	if failure := o.managementFailure(); failure != NoFailure {
+		i.fail(failure)
+		return PreparationDenied, nil
+	}
+	switch o.registry {
+	case RegistryUsable:
+		return AlreadyUsable, nil
+	case RegistryAbsent, RegistryNeedsMigration:
+		return PreparationAllowed, nil
+	default:
+		i.fail(o.registryFailure())
+		return PreparationDenied, nil
+	}
+}
+
+// RegistryPreparationResult 只能是安全失败或完整回读，不能表达裸操作成功。
+type RegistryPreparationResult struct {
+	observation CapabilityObservation
+	failure     Failure
+}
+
+func RegistryReadBack(o CapabilityObservation) RegistryPreparationResult {
+	return RegistryPreparationResult{observation: o}
+}
+
+func RegistryPreparationFailed(target ObservationTarget, failure Failure) (RegistryPreparationResult, error) {
+	if err := target.Validate(); err != nil {
+		return RegistryPreparationResult{}, err
+	}
+	if failure < ObservationIncomplete || failure > RegistryNotUsable {
+		return RegistryPreparationResult{}, errors.New("registry preparation requires a known failure category")
+	}
+	return RegistryPreparationResult{observation: CapabilityObservation{target: target}, failure: failure}, nil
+}
+
+func (i *Instance) AssessRegistryResult(result RegistryPreparationResult) error {
+	o := result.observation
+	if err := i.acceptObservation(o, PhaseInitializingRegistry); err != nil {
+		return err
+	}
+	if result.failure != NoFailure {
+		i.fail(result.failure)
+		return nil
+	}
+	i.assessComplete(o)
+	return nil
+}
+
+func (i *Instance) assessComplete(o CapabilityObservation) {
+	if failure := o.managementFailure(); failure != NoFailure {
+		i.fail(failure)
+		return
+	}
+	if failure := o.registryFailure(); failure != NoFailure {
+		i.fail(failure)
+		return
+	}
+	i.snapshot = Snapshot{Phase: PhaseReady, ObservedRevision: i.target.Revision().Value(),
+		Readiness: Ready, ReportedVersion: o.version}
+	i.evidence = &o
+}
+
+// AssessReadiness 每轮接收完整事实，失败立即撤销本轮供应能力。
+func (i *Instance) AssessReadiness(o CapabilityObservation) error {
+	if err := i.acceptObservation(o, PhaseReady); err != nil {
+		return err
+	}
+	if i.snapshot.ObservedRevision != i.target.Revision().Value() {
+		return i.BeginValidation()
+	}
+	if o.managementFailure() != NoFailure || o.registry == RegistryUnavailable {
+		i.snapshot.Phase = PhaseValidating
+	} else if o.registryFailure() != NoFailure {
+		i.snapshot.Phase = PhaseInitializingRegistry
+	}
+	i.assessComplete(o)
+	return nil
+}
+
+// RequireProvisioningReady 仅检查 Instance 前置条件，不授予 Tenant 所有权或外部写入许可。
+func (i *Instance) RequireProvisioningReady() error {
+	if i.deleting || i.evidence == nil || i.snapshot.Phase != PhaseReady || i.snapshot.Readiness != Ready ||
+		i.snapshot.ObservedRevision != i.target.Revision().Value() {
+		return errors.New("instance is not ready for provisioning")
+	}
+	return nil
+}

internal/database/domain/instance/readiness_test.go

@@ -0,0 +1,352 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+const testServerVersion = "17.6"
+
+func completeChecks() instance.ManagementChecks {
+	return instance.ManagementChecks{
+		Connection: instance.CheckPassed, Metadata: instance.CheckPassed,
+		Roles: instance.CheckPassed, Databases: instance.CheckPassed,
+		Grants: instance.CheckPassed, Extensions: instance.CheckPassed,
+	}
+}
+
+func capability(t *testing.T, value *instance.Instance, checks instance.ManagementChecks,
+	registry instance.RegistryState,
+) instance.CapabilityObservation {
+	t.Helper()
+	o, err := instance.NewCapabilityObservation(value.Target(), testServerVersion, checks, registry)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return o
+}
+
+func readyInstance(t *testing.T) *instance.Instance {
+	t.Helper()
+	i := lifecycleInstance(t, instance.Snapshot{Phase: instance.PhaseInitializingRegistry}, false)
+	if err := i.AssessRegistryResult(instance.RegistryReadBack(capability(t, i, completeChecks(), instance.RegistryUsable))); err != nil {
+		t.Fatal(err)
+	}
+	if err := i.RequireProvisioningReady(); err != nil {
+		t.Fatal(err)
+	}
+	return i
+}
+
+func TestReadinessRequiresCompleteReadBack(t *testing.T) {
+	i := lifecycleInstance(t, instance.Snapshot{}, false)
+	if err := i.BeginValidation(); err != nil {
+		t.Fatal(err)
+	}
+	absent := capability(t, i, completeChecks(), instance.RegistryAbsent)
+	if err := i.AssessManagement(absent); err != nil {
+		t.Fatal(err)
+	}
+	if s := i.Snapshot(); s.Phase != instance.PhaseInitializingRegistry || s.ObservedRevision != 0 || s.Readiness != instance.Unknown {
+		t.Fatalf("management observation prematurely concluded readiness: %+v", s)
+	}
+	for range 2 {
+		decision, err := i.PlanRegistryPreparation(absent)
+		if err != nil || decision != instance.PreparationAllowed {
+			t.Fatalf("preparation: %v, %v", decision, err)
+		}
+		if i.RequireProvisioningReady() == nil {
+			t.Fatal("preparation authorized provisioning")
+		}
+	}
+	if err := i.AssessRegistryResult(instance.RegistryReadBack(absent)); err != nil {
+		t.Fatal(err)
+	}
+	if i.Snapshot().Failure != instance.RegistryNotUsable || i.RequireProvisioningReady() == nil {
+		t.Fatal("absent registry accepted as ready")
+	}
+	usable := capability(t, i, completeChecks(), instance.RegistryUsable)
+	decision, err := i.PlanRegistryPreparation(usable)
+	if err != nil || decision != instance.AlreadyUsable {
+		t.Fatalf("retry after external preparation: %v, %v", decision, err)
+	}
+	if err := i.AssessRegistryResult(instance.RegistryReadBack(usable)); err != nil {
+		t.Fatal(err)
+	}
+	if s := i.Snapshot(); s.Readiness != instance.Ready || s.ReportedVersion != testServerVersion || s.ObservedRevision != i.Target().Revision().Value() {
+		t.Fatalf("complete observation not accepted: %+v", s)
+	}
+	if err := i.RequireProvisioningReady(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// 重启只恢复 checkpoint；依赖稍后恢复时必须重新取得完整事实。
+func TestReadinessRecoveryAndInvalidation(t *testing.T) {
+	i := readyInstance(t)
+	restored, err := instance.Reconstitute(i.Target(), i.Snapshot(), false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if restored.RequireProvisioningReady() == nil {
+		t.Fatal("persisted Ready fabricated fresh evidence")
+	}
+	for range 2 {
+		if err := restored.AssessReadiness(capability(t, restored, completeChecks(), instance.RegistryUsable)); err != nil {
+			t.Fatal(err)
+		}
+		if err := restored.RequireProvisioningReady(); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := restored.BeginValidation(); err != nil {
+		t.Fatal(err)
+	}
+	if restored.RequireProvisioningReady() == nil {
+		t.Fatal("validation retained evidence")
+	}
+	deleted, err := instance.Reconstitute(i.Target(), i.Snapshot(), true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if deleted.RequireProvisioningReady() == nil {
+		t.Fatal("deletion allowed provisioning")
+	}
+	if err := deleted.BeginDeletion(); err != nil {
+		t.Fatal(err)
+	}
+	if deleted.RequireProvisioningReady() == nil {
+		t.Fatal("deleting checkpoint allowed provisioning")
+	}
+}
+
+func TestEachManagementCheckIsRequired(t *testing.T) {
+	for field := range 6 {
+		for _, result := range []instance.CheckResult{instance.CheckUnobserved, instance.CheckUnavailable,
+			instance.CheckAuthenticationFailed, instance.CheckInsufficientPrivileges, 255} {
+			checks := completeChecks()
+			fields := []*instance.CheckResult{&checks.Connection, &checks.Metadata, &checks.Roles,
+				&checks.Databases, &checks.Grants, &checks.Extensions}
+			*fields[field] = result
+			i := readyInstance(t)
+			if err := i.AssessReadiness(capability(t, i, checks, instance.RegistryUsable)); err != nil {
+				t.Fatal(err)
+			}
+			if s := i.Snapshot(); s.Phase != instance.PhaseValidating || s.Readiness != instance.NotReady ||
+				s.Failure == instance.NoFailure || i.RequireProvisioningReady() == nil {
+				t.Fatalf("check %d result %d accepted: %+v", field, result, s)
+			}
+		}
+	}
+}
+
+func TestRegistryDecisionsAndReadinessLoss(t *testing.T) {
+	for _, tc := range []struct {
+		state    instance.RegistryState
+		decision instance.PreparationDecision
+		failure  instance.Failure
+	}{
+		{instance.RegistryUsable, instance.AlreadyUsable, instance.NoFailure},
+		{instance.RegistryAbsent, instance.PreparationAllowed, instance.RegistryNotUsable},
+		{instance.RegistryNeedsMigration, instance.PreparationAllowed, instance.RegistryNotUsable},
+		{instance.RegistryUnsupported, instance.PreparationDenied, instance.RegistryIncompatible},
+		{instance.RegistryUnavailable, instance.PreparationDenied, instance.DependencyUnavailable},
+		{instance.RegistryUnobserved, instance.PreparationDenied, instance.ObservationIncomplete},
+		{255, instance.PreparationDenied, instance.ObservationIncomplete},
+	} {
+		i := lifecycleInstance(t, instance.Snapshot{Phase: instance.PhaseInitializingRegistry}, false)
+		o := capability(t, i, completeChecks(), tc.state)
+		decision, err := i.PlanRegistryPreparation(o)
+		if err != nil || decision != tc.decision {
+			t.Fatalf("registry %d: %v, %v", tc.state, decision, err)
+		}
+		i = readyInstance(t)
+		if err := i.AssessReadiness(o); err != nil {
+			t.Fatal(err)
+		}
+		if i.Snapshot().Failure != tc.failure {
+			t.Fatalf("registry %d: %+v", tc.state, i.Snapshot())
+		}
+		if tc.state != instance.RegistryUsable {
+			wantPhase := instance.PhaseInitializingRegistry
+			if tc.state == instance.RegistryUnavailable {
+				wantPhase = instance.PhaseValidating
+			}
+			if i.Snapshot().Phase != wantPhase || i.RequireProvisioningReady() == nil {
+				t.Fatal("registry drift retained readiness")
+			}
+		}
+	}
+}
+
+func TestInitializationRejectsIncompleteOrFailedManagement(t *testing.T) {
+	for _, tc := range []struct {
+		checks   instance.ManagementChecks
+		registry instance.RegistryState
+		failure  instance.Failure
+	}{
+		{instance.ManagementChecks{}, instance.RegistryUsable, instance.ObservationIncomplete},
+		{completeChecks(), instance.RegistryUnsupported, instance.RegistryIncompatible},
+		{completeChecks(), instance.RegistryUnavailable, instance.DependencyUnavailable},
+	} {
+		i := lifecycleInstance(t, instance.Snapshot{Phase: instance.PhaseValidating}, false)
+		if err := i.AssessManagement(capability(t, i, tc.checks, tc.registry)); err != nil {
+			t.Fatal(err)
+		}
+		if s := i.Snapshot(); s.Phase != instance.PhaseValidating || s.Failure != tc.failure ||
+			s.ObservedRevision != i.Target().Revision().Value() || s.Readiness != instance.NotReady {
+			t.Fatalf("invalid management accepted: %+v", s)
+		}
+	}
+	i := lifecycleInstance(t, instance.Snapshot{Phase: instance.PhaseInitializingRegistry}, false)
+	decision, err := i.PlanRegistryPreparation(capability(t, i, instance.ManagementChecks{}, instance.RegistryAbsent))
+	if err != nil || decision != instance.PreparationDenied || i.Snapshot().Failure != instance.ObservationIncomplete {
+		t.Fatal("incomplete management allowed registry writes")
+	}
+	if err := i.AssessRegistryResult(instance.RegistryReadBack(capability(t, i, completeChecks(), instance.RegistryUsable))); err != nil {
+		t.Fatal(err)
+	}
+	if err := i.RequireProvisioningReady(); err != nil {
+		t.Fatal("dependency recovery did not restore readiness", err)
+	}
+}
+
+func TestReadinessMethodsRejectWrongPhaseAndDeletion(t *testing.T) {
+	for _, deleting := range []bool{false, true} {
+		for _, phase := range []instance.Phase{instance.PhasePending, instance.PhaseValidating,
+			instance.PhaseInitializingRegistry, instance.PhaseReady, instance.PhaseDeleting} {
+			for _, operation := range []struct {
+				phase instance.Phase
+				apply func(*instance.Instance, instance.CapabilityObservation) error
+			}{
+				{instance.PhaseValidating, (*instance.Instance).AssessManagement},
+				{instance.PhaseReady, (*instance.Instance).AssessReadiness},
+				{instance.PhaseInitializingRegistry, func(i *instance.Instance, o instance.CapabilityObservation) error {
+					_, err := i.PlanRegistryPreparation(o)
+					return err
+				}},
+				{instance.PhaseInitializingRegistry, func(i *instance.Instance, o instance.CapabilityObservation) error {
+					return i.AssessRegistryResult(instance.RegistryReadBack(o))
+				}},
+			} {
+				if !deleting && operation.phase == phase {
+					continue
+				}
+				i := lifecycleInstance(t, instance.Snapshot{Phase: phase}, deleting)
+				before := i.Snapshot()
+				if err := operation.apply(i, capability(t, i, completeChecks(), instance.RegistryUsable)); err == nil {
+					t.Fatalf("phase %s deleting=%t accepted operation for %s", phase, deleting, operation.phase)
+				}
+				if i.Snapshot() != before {
+					t.Fatal("rejected operation mutated snapshot")
+				}
+			}
+		}
+	}
+}
+
+func TestOldGenerationObservationDoesNotReplaceEvidence(t *testing.T) {
+	i := readyInstance(t)
+	target := i.Target()
+	revision, err := instance.NewRevision(target.Revision().Value() + 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	other, err := instance.NewObservationTarget(target.Identity(), revision, target.Definition())
+	if err != nil {
+		t.Fatal(err)
+	}
+	o, err := instance.NewCapabilityObservation(other, testServerVersion, completeChecks(), instance.RegistryUsable)
+	if err != nil {
+		t.Fatal(err)
+	}
+	before := i.Snapshot()
+	if err := i.AssessReadiness(o); err == nil || i.Snapshot() != before {
+		t.Fatal("mismatched generation observation was accepted")
+	}
+	if err := i.RequireProvisioningReady(); err != nil {
+		t.Fatal("rejected unrelated input changed previously accepted evidence", err)
+	}
+}
+
+func TestPreparationFailureCannotEstablishReadiness(t *testing.T) {
+	i := lifecycleInstance(t, instance.Snapshot{Phase: instance.PhaseInitializingRegistry}, false)
+	for _, failure := range []instance.Failure{instance.DependencyUnavailable, instance.AuthenticationFailed,
+		instance.InsufficientPrivileges, instance.RegistryIncompatible} {
+		result, err := instance.RegistryPreparationFailed(i.Target(), failure)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := i.AssessRegistryResult(result); err != nil {
+			t.Fatal(err)
+		}
+		if s := i.Snapshot(); s.Failure != failure || s.Readiness != instance.NotReady ||
+			s.Phase != instance.PhaseInitializingRegistry || i.RequireProvisioningReady() == nil {
+			t.Fatalf("failed operation accepted: %+v", s)
+		}
+	}
+	for _, failure := range []instance.Failure{instance.NoFailure, 255} {
+		if _, err := instance.RegistryPreparationFailed(i.Target(), failure); err == nil {
+			t.Fatal("invalid failure accepted")
+		}
+	}
+}
+
+func TestCapabilityInputsAndLifecycleGuards(t *testing.T) {
+	i := readyInstance(t)
+	if _, err := instance.NewCapabilityObservation(instance.ObservationTarget{}, testServerVersion,
+		completeChecks(), instance.RegistryUsable); err == nil {
+		t.Fatal("invalid target accepted")
+	}
+	if _, err := instance.RegistryPreparationFailed(instance.ObservationTarget{}, instance.DependencyUnavailable); err == nil {
+		t.Fatal("invalid failure target accepted")
+	}
+	for _, method := range []func(instance.CapabilityObservation) error{
+		i.AssessManagement, i.AssessReadiness,
+		func(o instance.CapabilityObservation) error { _, err := i.PlanRegistryPreparation(o); return err },
+		func(o instance.CapabilityObservation) error {
+			return i.AssessRegistryResult(instance.RegistryReadBack(o))
+		},
+	} {
+		before := i.Snapshot()
+		if err := method(instance.CapabilityObservation{}); err == nil || i.Snapshot() != before {
+			t.Fatal("mismatched observation accepted or mutated state")
+		}
+	}
+	old := i.Snapshot()
+	old.ObservedRevision = 0
+	changed := lifecycleInstance(t, old, false)
+	if err := changed.AssessReadiness(capability(t, changed, completeChecks(), instance.RegistryUsable)); err != nil {
+		t.Fatal(err)
+	}
+	if s := changed.Snapshot(); s.Phase != instance.PhaseValidating || s.ObservedRevision != 0 || s.Readiness != instance.Unknown {
+		t.Fatalf("changed generation accepted old checkpoint: %+v", s)
+	}
+	o, err := instance.NewCapabilityObservation(i.Target(), "", completeChecks(), instance.RegistryUsable)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := i.AssessReadiness(o); err != nil {
+		t.Fatal(err)
+	}
+	if i.Snapshot().Failure != instance.ObservationIncomplete {
+		t.Fatal("missing version accepted")
+	}
+}