add per-container item collision enumeration (#3629)

populates the item collision cache generators for all exchange data types.  Next we'll use these to compare the items being restored for collision before making post requests, by populating this cache at the top of each collection restore process.

---

#### Does this PR need a docs update or release note?

- [x] ⛔ No

#### Type of change

- [x] 🌻 Feature

#### Issue(s)

* #3562

#### Test Plan

- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/m365/onedrive/mock/handlers.go

@@ -228,7 +228,7 @@ func (m GetsItemPermission) GetItemPermission(
 
 // ---------------------------------------------------------------------------
 // Restore Handler
-// ---------------------------------------------------------------------------
+// --------------------------------------------------------------------------
 
 type RestoreHandler struct {
 	ItemInfo details.ItemInfo

src/pkg/services/m365/api/config.go

@@ -17,8 +17,15 @@ const (
 // get easily misspelled.
 // eg: we don't need a const for "id"
 const (
-	parentFolderID    = "parentFolderId"
+	attendees         = "attendees"
+	bccRecipients     = "bccRecipients"
+	ccRecipients      = "ccRecipients"
+	createdDateTime   = "createdDateTime"
 	displayName       = "displayName"
+	givenName         = "givenName"
+	parentFolderID    = "parentFolderId"
+	surname           = "surname"
+	toRecipients      = "toRecipients"
 	userPrincipalName = "userPrincipalName"
 )
 

src/pkg/services/m365/api/contacts.go

@@ -265,3 +265,17 @@ func ContactInfo(contact models.Contactable) *details.ExchangeInfo {
 		Modified:    ptr.OrNow(contact.GetLastModifiedDateTime()),
 	}
 }
+
+func contactCollisionKeyProps() []string {
+	return idAnd(givenName)
+}
+
+// ContactCollisionKey constructs a key from the contactable's creation time and either displayName or given+surname.
+// collision keys are used to identify duplicate item conflicts for handling advanced restoration config.
+func ContactCollisionKey(item models.Contactable) string {
+	if item == nil {
+		return ""
+	}
+
+	return ptr.Val(item.GetId())
+}

src/pkg/services/m365/api/contacts_pager.go

@@ -90,32 +90,74 @@ func (c Contacts) EnumerateContainers(
 // item pager
 // ---------------------------------------------------------------------------
 
-var _ itemPager[models.Contactable] = &contactsPager{}
+var _ itemPager[models.Contactable] = &contactsPageCtrl{}
 
-type contactsPager struct {
-	// TODO(rkeeprs)
+type contactsPageCtrl struct {
+	gs      graph.Servicer
+	builder *users.ItemContactFoldersItemContactsRequestBuilder
+	options *users.ItemContactFoldersItemContactsRequestBuilderGetRequestConfiguration
 }
 
-func (c Contacts) NewContactsPager() itemPager[models.Contactable] {
-	// TODO(rkeepers)
-	return nil
+func (c Contacts) NewContactsPager(
+	userID, containerID string,
+	selectProps ...string,
+) itemPager[models.Contactable] {
+	options := &users.ItemContactFoldersItemContactsRequestBuilderGetRequestConfiguration{
+		Headers: newPreferHeaders(preferPageSize(maxNonDeltaPageSize)),
+	}
+
+	if len(selectProps) > 0 {
+		options.QueryParameters = &users.ItemContactFoldersItemContactsRequestBuilderGetQueryParameters{
+			Select: selectProps,
+		}
+	}
+
+	builder := c.Stable.
+		Client().
+		Users().
+		ByUserId(userID).
+		ContactFolders().
+		ByContactFolderId(containerID).
+		Contacts()
+
+	return &contactsPageCtrl{c.Stable, builder, options}
 }
 
 //lint:ignore U1000 False Positive
-func (p *contactsPager) getPage(ctx context.Context) (PageLinker, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (p *contactsPageCtrl) getPage(ctx context.Context) (PageLinkValuer[models.Contactable], error) {
+	resp, err := p.builder.Get(ctx, p.options)
+	if err != nil {
+		return nil, graph.Stack(ctx, err)
+	}
+
+	return EmptyDeltaLinker[models.Contactable]{PageLinkValuer: resp}, nil
 }
 
 //lint:ignore U1000 False Positive
-func (p *contactsPager) setNext(nextLink string) {
-	// TODO(rkeepers)
+func (p *contactsPageCtrl) setNext(nextLink string) {
+	p.builder = users.NewItemContactFoldersItemContactsRequestBuilder(nextLink, p.gs.Adapter())
 }
 
 //lint:ignore U1000 False Positive
-func (p *contactsPager) valuesIn(pl PageLinker) ([]models.Contactable, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (c Contacts) GetItemsInContainerByCollisionKey(
+	ctx context.Context,
+	userID, containerID string,
+) (map[string]string, error) {
+	ctx = clues.Add(ctx, "container_id", containerID)
+	pager := c.NewContactsPager(userID, containerID, contactCollisionKeyProps()...)
+
+	items, err := enumerateItems(ctx, pager)
+	if err != nil {
+		return nil, graph.Wrap(ctx, err, "enumerating contacts")
+	}
+
+	m := map[string]string{}
+
+	for _, item := range items {
+		m[ContactCollisionKey(item)] = ptr.Val(item.GetId())
+	}
+
+	return m, nil
 }
 
 // ---------------------------------------------------------------------------

src/pkg/services/m365/api/contacts_pager_test.go

@@ -0,0 +1,73 @@
+package api_test
+
+import (
+	"testing"
+
+	"github.com/alcionai/clues"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/alcionai/corso/src/internal/common/ptr"
+	"github.com/alcionai/corso/src/internal/tester"
+	"github.com/alcionai/corso/src/pkg/services/m365/api"
+)
+
+type ContactsPagerIntgSuite struct {
+	tester.Suite
+	cts clientTesterSetup
+}
+
+func TestContactsPagerIntgSuite(t *testing.T) {
+	suite.Run(t, &ContactsPagerIntgSuite{
+		Suite: tester.NewIntegrationSuite(
+			t,
+			[][]string{tester.M365AcctCredEnvs}),
+	})
+}
+
+func (suite *ContactsPagerIntgSuite) SetupSuite() {
+	suite.cts = newClientTesterSetup(suite.T())
+}
+
+func (suite *ContactsPagerIntgSuite) TestGetItemsInContainerByCollisionKey() {
+	t := suite.T()
+	ac := suite.cts.ac.Contacts()
+
+	ctx, flush := tester.NewContext(t)
+	defer flush()
+
+	container, err := ac.GetContainerByID(ctx, suite.cts.userID, "contacts")
+	require.NoError(t, err, clues.ToCore(err))
+
+	conts, err := ac.Stable.
+		Client().
+		Users().
+		ByUserId(suite.cts.userID).
+		ContactFolders().
+		ByContactFolderId(ptr.Val(container.GetId())).
+		Contacts().
+		Get(ctx, nil)
+	require.NoError(t, err, clues.ToCore(err))
+
+	cs := conts.GetValue()
+	expect := make([]string, 0, len(cs))
+
+	for _, c := range cs {
+		expect = append(expect, api.ContactCollisionKey(c))
+	}
+
+	results, err := ac.GetItemsInContainerByCollisionKey(ctx, suite.cts.userID, "contacts")
+	require.NoError(t, err, clues.ToCore(err))
+	require.Less(t, 0, len(results), "requires at least one result")
+
+	for k, v := range results {
+		assert.NotEmpty(t, k, "all keys should be populated")
+		assert.NotEmpty(t, v, "all values should be populated")
+	}
+
+	for _, e := range expect {
+		_, ok := results[e]
+		assert.Truef(t, ok, "expected results to contain collision key: %s", e)
+	}
+}

src/pkg/services/m365/api/events.go

@@ -698,3 +698,17 @@ func EventFromMap(ev map[string]any) (models.Eventable, error) {
 
 	return body, nil
 }
+
+func eventCollisionKeyProps() []string {
+	return idAnd("subject")
+}
+
+// EventCollisionKey constructs a key from the eventable's creation time, subject, and organizer.
+// collision keys are used to identify duplicate item conflicts for handling advanced restoration config.
+func EventCollisionKey(item models.Eventable) string {
+	if item == nil {
+		return ""
+	}
+
+	return ptr.Val(item.GetSubject())
+}

src/pkg/services/m365/api/events_pager.go

@@ -98,32 +98,74 @@ func (c Events) EnumerateContainers(
 // item pager
 // ---------------------------------------------------------------------------
 
-var _ itemPager[models.Eventable] = &eventsPager{}
+var _ itemPager[models.Eventable] = &eventsPageCtrl{}
 
-type eventsPager struct {
-	// TODO(rkeeprs)
+type eventsPageCtrl struct {
+	gs      graph.Servicer
+	builder *users.ItemCalendarsItemEventsRequestBuilder
+	options *users.ItemCalendarsItemEventsRequestBuilderGetRequestConfiguration
 }
 
-func (c Events) NewEventsPager() itemPager[models.Eventable] {
-	// TODO(rkeepers)
-	return nil
+func (c Events) NewEventsPager(
+	userID, containerID string,
+	selectProps ...string,
+) itemPager[models.Eventable] {
+	options := &users.ItemCalendarsItemEventsRequestBuilderGetRequestConfiguration{
+		Headers: newPreferHeaders(preferPageSize(maxNonDeltaPageSize)),
+	}
+
+	if len(selectProps) > 0 {
+		options.QueryParameters = &users.ItemCalendarsItemEventsRequestBuilderGetQueryParameters{
+			Select: selectProps,
+		}
+	}
+
+	builder := c.Stable.
+		Client().
+		Users().
+		ByUserId(userID).
+		Calendars().
+		ByCalendarId(containerID).
+		Events()
+
+	return &eventsPageCtrl{c.Stable, builder, options}
 }
 
 //lint:ignore U1000 False Positive
-func (p *eventsPager) getPage(ctx context.Context) (PageLinker, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (p *eventsPageCtrl) getPage(ctx context.Context) (PageLinkValuer[models.Eventable], error) {
+	resp, err := p.builder.Get(ctx, p.options)
+	if err != nil {
+		return nil, graph.Stack(ctx, err)
+	}
+
+	return resp, nil
 }
 
 //lint:ignore U1000 False Positive
-func (p *eventsPager) setNext(nextLink string) {
-	// TODO(rkeepers)
+func (p *eventsPageCtrl) setNext(nextLink string) {
+	p.builder = users.NewItemCalendarsItemEventsRequestBuilder(nextLink, p.gs.Adapter())
 }
 
 //lint:ignore U1000 False Positive
-func (p *eventsPager) valuesIn(pl PageLinker) ([]models.Eventable, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (c Events) GetItemsInContainerByCollisionKey(
+	ctx context.Context,
+	userID, containerID string,
+) (map[string]string, error) {
+	ctx = clues.Add(ctx, "container_id", containerID)
+	pager := c.NewEventsPager(userID, containerID, eventCollisionKeyProps()...)
+
+	items, err := enumerateItems(ctx, pager)
+	if err != nil {
+		return nil, graph.Wrap(ctx, err, "enumerating events")
+	}
+
+	m := map[string]string{}
+
+	for _, item := range items {
+		m[EventCollisionKey(item)] = ptr.Val(item.GetId())
+	}
+
+	return m, nil
 }
 
 // ---------------------------------------------------------------------------

src/pkg/services/m365/api/events_pager_test.go

@@ -0,0 +1,73 @@
+package api_test
+
+import (
+	"testing"
+
+	"github.com/alcionai/clues"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/alcionai/corso/src/internal/common/ptr"
+	"github.com/alcionai/corso/src/internal/tester"
+	"github.com/alcionai/corso/src/pkg/services/m365/api"
+)
+
+type EventsPagerIntgSuite struct {
+	tester.Suite
+	cts clientTesterSetup
+}
+
+func TestEventsPagerIntgSuite(t *testing.T) {
+	suite.Run(t, &EventsPagerIntgSuite{
+		Suite: tester.NewIntegrationSuite(
+			t,
+			[][]string{tester.M365AcctCredEnvs}),
+	})
+}
+
+func (suite *EventsPagerIntgSuite) SetupSuite() {
+	suite.cts = newClientTesterSetup(suite.T())
+}
+
+func (suite *EventsPagerIntgSuite) TestGetItemsInContainerByCollisionKey() {
+	t := suite.T()
+	ac := suite.cts.ac.Events()
+
+	ctx, flush := tester.NewContext(t)
+	defer flush()
+
+	container, err := ac.GetContainerByID(ctx, suite.cts.userID, "calendar")
+	require.NoError(t, err, clues.ToCore(err))
+
+	evts, err := ac.Stable.
+		Client().
+		Users().
+		ByUserId(suite.cts.userID).
+		Calendars().
+		ByCalendarId(ptr.Val(container.GetId())).
+		Events().
+		Get(ctx, nil)
+	require.NoError(t, err, clues.ToCore(err))
+
+	es := evts.GetValue()
+	expect := make([]string, 0, len(es))
+
+	for _, e := range es {
+		expect = append(expect, api.EventCollisionKey(e))
+	}
+
+	results, err := ac.GetItemsInContainerByCollisionKey(ctx, suite.cts.userID, "calendar")
+	require.NoError(t, err, clues.ToCore(err))
+	require.Less(t, 0, len(results), "requires at least one result")
+
+	for k, v := range results {
+		assert.NotEmpty(t, k, "all keys should be populated")
+		assert.NotEmpty(t, v, "all values should be populated")
+	}
+
+	for _, e := range expect {
+		_, ok := results[e]
+		assert.Truef(t, ok, "expected results to contain collision key: %s", e)
+	}
+}

src/pkg/services/m365/api/helper_test.go

@@ -0,0 +1,34 @@
+package api_test
+
+import (
+	"testing"
+
+	"github.com/alcionai/clues"
+	"github.com/stretchr/testify/require"
+
+	"github.com/alcionai/corso/src/internal/tester"
+	"github.com/alcionai/corso/src/pkg/services/m365/api"
+)
+
+type clientTesterSetup struct {
+	ac     api.Client
+	userID string
+}
+
+func newClientTesterSetup(t *testing.T) clientTesterSetup {
+	cts := clientTesterSetup{}
+
+	ctx, flush := tester.NewContext(t)
+	defer flush()
+
+	a := tester.NewM365Account(t)
+	creds, err := a.M365Config()
+	require.NoError(t, err, clues.ToCore(err))
+
+	cts.ac, err = api.NewClient(creds)
+	require.NoError(t, err, clues.ToCore(err))
+
+	cts.userID = tester.GetM365UserID(ctx)
+
+	return cts
+}

src/pkg/services/m365/api/item_pager.go

@@ -66,11 +66,9 @@ func (e EmptyDeltaLinker[T]) GetValue() []T {
 
 type itemPager[T any] interface {
 	// getPage get a page with the specified options from graph
-	getPage(context.Context) (PageLinker, error)
+	getPage(context.Context) (PageLinkValuer[T], error)
 	// setNext is used to pass in the next url got from graph
 	setNext(string)
-	// valuesIn gets us the values in a page
-	valuesIn(PageLinker) ([]T, error)
 }
 
 func enumerateItems[T any](
@@ -90,14 +88,7 @@ func enumerateItems[T any](
 			return nil, graph.Stack(ctx, err)
 		}
 
-		// each category type responds with a different interface, but all
-		// of them comply with GetValue, which is where we'll get our item data.
-		items, err := pager.valuesIn(resp)
-		if err != nil {
-			return nil, graph.Stack(ctx, err)
-		}
-
-		result = append(result, items...)
+		result = append(result, resp.GetValue()...)
 		nextLink = NextLink(resp)
 
 		pager.setNext(nextLink)

src/pkg/services/m365/api/item_pager_test.go

@@ -57,7 +57,9 @@ func (v testPagerValue) GetAdditionalData() map[string]any {
 
 // mock page
 
-type testPage struct{}
+type testPage struct {
+	values []any
+}
 
 func (p testPage) GetOdataNextLink() *string {
 	// no next, just one page
@@ -69,30 +71,28 @@ func (p testPage) GetOdataDeltaLink() *string {
 	return ptr.To("")
 }
 
+func (p testPage) GetValue() []any {
+	return p.values
+}
+
 // mock item pager
 
 var _ itemPager[any] = &testPager{}
 
 type testPager struct {
-	t         *testing.T
-	items     []any
-	pageErr   error
-	valuesErr error
+	t       *testing.T
+	pager   testPage
+	pageErr error
 }
 
 //lint:ignore U1000 False Positive
-func (p *testPager) getPage(ctx context.Context) (PageLinker, error) {
-	return testPage{}, p.pageErr
+func (p *testPager) getPage(ctx context.Context) (PageLinkValuer[any], error) {
+	return p.pager, p.pageErr
 }
 
 //lint:ignore U1000 False Positive
 func (p *testPager) setNext(nextLink string) {}
 
-//lint:ignore U1000 False Positive
-func (p *testPager) valuesIn(pl PageLinker) ([]any, error) {
-	return p.items, p.valuesErr
-}
-
 // mock id pager
 
 var _ itemIDPager = &testIDsPager{}
@@ -169,26 +169,12 @@ func (suite *ItemPagerUnitSuite) TestEnumerateItems() {
 			) itemPager[any] {
 				return &testPager{
 					t:     t,
-					items: []any{"foo", "bar"},
+					pager: testPage{[]any{"foo", "bar"}},
 				}
 			},
 			expect:    []any{"foo", "bar"},
 			expectErr: require.NoError,
 		},
-		{
-			name: "get values err",
-			getPager: func(
-				t *testing.T,
-				ctx context.Context,
-			) itemPager[any] {
-				return &testPager{
-					t:         t,
-					valuesErr: assert.AnError,
-				}
-			},
-			expect:    nil,
-			expectErr: require.Error,
-		},
 		{
 			name: "next page err",
 			getPager: func(
@@ -212,7 +198,7 @@ func (suite *ItemPagerUnitSuite) TestEnumerateItems() {
 			ctx, flush := tester.NewContext(t)
 			defer flush()
 
-			result, err := enumerateItems[any](ctx, test.getPager(t, ctx))
+			result, err := enumerateItems(ctx, test.getPager(t, ctx))
 			test.expectErr(t, err, clues.ToCore(err))
 
 			require.EqualValues(t, test.expect, result)

src/pkg/services/m365/api/mail.go

@@ -540,3 +540,17 @@ func UnwrapEmailAddress(contact models.Recipientable) string {
 
 	return ptr.Val(contact.GetEmailAddress().GetAddress())
 }
+
+func mailCollisionKeyProps() []string {
+	return idAnd("subject")
+}
+
+// MailCollisionKey constructs a key from the messageable's subject, sender, and recipients (to, cc, bcc).
+// collision keys are used to identify duplicate item conflicts for handling advanced restoration config.
+func MailCollisionKey(item models.Messageable) string {
+	if item == nil {
+		return ""
+	}
+
+	return ptr.Val(item.GetSubject())
+}

src/pkg/services/m365/api/mail_pager.go

@@ -121,32 +121,52 @@ func (c Mail) EnumerateContainers(
 // item pager
 // ---------------------------------------------------------------------------
 
-var _ itemPager[models.Messageable] = &mailPager{}
+var _ itemPager[models.Messageable] = &mailPageCtrl{}
 
-type mailPager struct {
-	// TODO(rkeeprs)
+type mailPageCtrl struct {
+	gs      graph.Servicer
+	builder *users.ItemMailFoldersItemMessagesRequestBuilder
+	options *users.ItemMailFoldersItemMessagesRequestBuilderGetRequestConfiguration
 }
 
-func (c Mail) NewMailPager() itemPager[models.Messageable] {
-	// TODO(rkeepers)
-	return nil
+func (c Mail) NewMailPager(
+	userID, containerID string,
+	selectProps ...string,
+) itemPager[models.Messageable] {
+	options := &users.ItemMailFoldersItemMessagesRequestBuilderGetRequestConfiguration{
+		Headers: newPreferHeaders(preferPageSize(maxNonDeltaPageSize)),
+	}
+
+	if len(selectProps) > 0 {
+		options.QueryParameters = &users.ItemMailFoldersItemMessagesRequestBuilderGetQueryParameters{
+			Select: selectProps,
+		}
+	}
+
+	builder := c.Stable.
+		Client().
+		Users().
+		ByUserId(userID).
+		MailFolders().
+		ByMailFolderId(containerID).
+		Messages()
+
+	return &mailPageCtrl{c.Stable, builder, options}
 }
 
 //lint:ignore U1000 False Positive
-func (p *mailPager) getPage(ctx context.Context) (PageLinker, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (p *mailPageCtrl) getPage(ctx context.Context) (PageLinkValuer[models.Messageable], error) {
+	page, err := p.builder.Get(ctx, p.options)
+	if err != nil {
+		return nil, graph.Stack(ctx, err)
+	}
+
+	return EmptyDeltaLinker[models.Messageable]{PageLinkValuer: page}, nil
 }
 
 //lint:ignore U1000 False Positive
-func (p *mailPager) setNext(nextLink string) {
-	// TODO(rkeepers)
-}
-
-//lint:ignore U1000 False Positive
-func (p *mailPager) valuesIn(pl PageLinker) ([]models.Messageable, error) {
-	// TODO(rkeepers)
-	return nil, nil
+func (p *mailPageCtrl) setNext(nextLink string) {
+	p.builder = users.NewItemMailFoldersItemMessagesRequestBuilder(nextLink, p.gs.Adapter())
 }
 
 // ---------------------------------------------------------------------------
@@ -204,6 +224,27 @@ func (p *mailIDPager) valuesIn(pl PageLinker) ([]getIDAndAddtler, error) {
 	return toValues[models.Messageable](pl)
 }
 
+func (c Mail) GetItemsInContainerByCollisionKey(
+	ctx context.Context,
+	userID, containerID string,
+) (map[string]string, error) {
+	ctx = clues.Add(ctx, "container_id", containerID)
+	pager := c.NewMailPager(userID, containerID, mailCollisionKeyProps()...)
+
+	items, err := enumerateItems(ctx, pager)
+	if err != nil {
+		return nil, graph.Wrap(ctx, err, "enumerating mail")
+	}
+
+	m := map[string]string{}
+
+	for _, item := range items {
+		m[MailCollisionKey(item)] = ptr.Val(item.GetId())
+	}
+
+	return m, nil
+}
+
 // ---------------------------------------------------------------------------
 // delta item ID pager
 // ---------------------------------------------------------------------------

src/pkg/services/m365/api/mail_pager_test.go

@@ -0,0 +1,73 @@
+package api_test
+
+import (
+	"testing"
+
+	"github.com/alcionai/clues"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/alcionai/corso/src/internal/common/ptr"
+	"github.com/alcionai/corso/src/internal/tester"
+	"github.com/alcionai/corso/src/pkg/services/m365/api"
+)
+
+type MailPagerIntgSuite struct {
+	tester.Suite
+	cts clientTesterSetup
+}
+
+func TestMailPagerIntgSuite(t *testing.T) {
+	suite.Run(t, &MailPagerIntgSuite{
+		Suite: tester.NewIntegrationSuite(
+			t,
+			[][]string{tester.M365AcctCredEnvs}),
+	})
+}
+
+func (suite *MailPagerIntgSuite) SetupSuite() {
+	suite.cts = newClientTesterSetup(suite.T())
+}
+
+func (suite *MailPagerIntgSuite) TestGetItemsInContainerByCollisionKey() {
+	t := suite.T()
+	ac := suite.cts.ac.Mail()
+
+	ctx, flush := tester.NewContext(t)
+	defer flush()
+
+	container, err := ac.GetContainerByID(ctx, suite.cts.userID, "inbox")
+	require.NoError(t, err, clues.ToCore(err))
+
+	msgs, err := ac.Stable.
+		Client().
+		Users().
+		ByUserId(suite.cts.userID).
+		MailFolders().
+		ByMailFolderId(ptr.Val(container.GetId())).
+		Messages().
+		Get(ctx, nil)
+	require.NoError(t, err, clues.ToCore(err))
+
+	ms := msgs.GetValue()
+	expect := make([]string, 0, len(ms))
+
+	for _, m := range ms {
+		expect = append(expect, api.MailCollisionKey(m))
+	}
+
+	results, err := ac.GetItemsInContainerByCollisionKey(ctx, suite.cts.userID, "inbox")
+	require.NoError(t, err, clues.ToCore(err))
+	require.Less(t, 0, len(results), "requires at least one result")
+
+	for k, v := range results {
+		assert.NotEmpty(t, k, "all keys should be populated")
+		assert.NotEmpty(t, v, "all values should be populated")
+	}
+
+	for _, e := range expect {
+		_, ok := results[e]
+		assert.Truef(t, ok, "expected results to contain collision key: %s", e)
+	}
+}