test sparse schedule placement

backend/tests/Feature/Schedule/ScheduleEndpointTest.php

@@ -196,6 +196,40 @@ class ScheduleEndpointTest extends TestCase
         $this->assertDatabaseCount('schedules', 1);
     }
 
+    public function test_it_packs_sparse_assignments_at_the_requested_end(): void
+    {
+        $user = $this->createUser('reader@example.com');
+        $set = $this->createSet($user, 'Course');
+        $lessonLevel = $this->createLevel($set, 'lesson');
+        $repository = app(ElementRepository::class);
+
+        foreach (range(1, 4) as $number) {
+            $repository->create(new CreateElementDto(
+                name: "Lesson {$number}",
+                level: $lessonLevel,
+                parentElement: null,
+            ));
+        }
+        $this->createSession($user, 'valid-token');
+
+        $response = $this->credentialedPost('/api/schedules', [
+            'setId' => $set->getId(),
+            'levelId' => $lessonLevel->getId(),
+            'startDate' => '2026-08-10',
+            'targetDate' => '2026-08-15',
+            'workloadPlacement' => 'end',
+        ])->assertCreated();
+
+        $days = $response->json('schedule.days');
+        $this->assertIsArray($days);
+        $this->assertSame(
+            [0, 0, 1, 1, 1, 1],
+            array_map(function (array $day): int {
+                return count($day['assignments']);
+            }, $days),
+        );
+    }
+
     public function test_it_rejects_an_unknown_workload_placement(): void
     {
         $user = $this->createUser('reader@example.com');
@@ -215,7 +249,34 @@ class ScheduleEndpointTest extends TestCase
             'targetDate' => '2026-08-14',
             'workloadPlacement' => 'sideways',
         ])->assertBadRequest()->assertExactJson([
-            'error' => 'workloadPlacement must be start, middle, or end',
+            'error' => 'workloadPlacement must be spread, start, middle, or end',
+        ]);
+    }
+
+    public function test_it_rejects_spread_placement_for_a_dense_schedule(): void
+    {
+        $user = $this->createUser('reader@example.com');
+        $set = $this->createSet($user, 'Course');
+        $lessonLevel = $this->createLevel($set, 'lesson');
+        $repository = app(ElementRepository::class);
+
+        foreach (range(1, 5) as $number) {
+            $repository->create(new CreateElementDto(
+                name: "Lesson {$number}",
+                level: $lessonLevel,
+                parentElement: null,
+            ));
+        }
+        $this->createSession($user, 'valid-token');
+
+        $this->credentialedPost('/api/schedules', [
+            'setId' => $set->getId(),
+            'levelId' => $lessonLevel->getId(),
+            'startDate' => '2026-08-10',
+            'targetDate' => '2026-08-13',
+            'workloadPlacement' => 'spread',
+        ])->assertBadRequest()->assertExactJson([
+            'error' => 'spread placement requires fewer assignments than days',
         ]);
     }
 

backend/tests/Unit/Schedule/EvenDistributionSchedulerTest.php

@@ -58,20 +58,75 @@ class EvenDistributionSchedulerTest extends TestCase
         }
     }
 
-    public function test_it_preserves_sparse_distribution_across_the_full_range(): void
+    public function test_it_places_sparse_assignments_at_the_requested_position(): void
     {
-        $dates = (new EvenDistributionScheduler)->scheduledDates(
+        $scheduler = new EvenDistributionScheduler;
-            assignmentCount: 3,
+        $expectedDates = [
+            WorkloadPlacement::Spread->value => [
+                '2026-08-10',
+                '2026-08-12',
+                '2026-08-13',
+                '2026-08-15',
+            ],
+            WorkloadPlacement::Start->value => [
+                '2026-08-10',
+                '2026-08-11',
+                '2026-08-12',
+                '2026-08-13',
+            ],
+            WorkloadPlacement::Middle->value => [
+                '2026-08-11',
+                '2026-08-12',
+                '2026-08-13',
+                '2026-08-14',
+            ],
+            WorkloadPlacement::End->value => [
+                '2026-08-12',
+                '2026-08-13',
+                '2026-08-14',
+                '2026-08-15',
+            ],
+        ];
+
+        foreach (WorkloadPlacement::cases() as $placement) {
+            $dates = $scheduler->scheduledDates(
+                assignmentCount: 4,
                 startDate: $this->utc('2026-08-10'),
-            targetDate: $this->utc('2026-08-16'),
+                targetDate: $this->utc('2026-08-15'),
-            workloadPlacement: WorkloadPlacement::Middle,
+                workloadPlacement: $placement,
             );
 
             $this->assertSame(
-            ['2026-08-10', '2026-08-13', '2026-08-16'],
+                $expectedDates[$placement->value],
                 $this->formattedDates($dates),
             );
         }
+    }
+
+    public function test_it_places_one_assignment_at_the_requested_position(): void
+    {
+        $scheduler = new EvenDistributionScheduler;
+        $expectedDates = [
+            WorkloadPlacement::Spread->value => '2026-08-10',
+            WorkloadPlacement::Start->value => '2026-08-10',
+            WorkloadPlacement::Middle->value => '2026-08-12',
+            WorkloadPlacement::End->value => '2026-08-15',
+        ];
+
+        foreach (WorkloadPlacement::cases() as $placement) {
+            $dates = $scheduler->scheduledDates(
+                assignmentCount: 1,
+                startDate: $this->utc('2026-08-10'),
+                targetDate: $this->utc('2026-08-15'),
+                workloadPlacement: $placement,
+            );
+
+            $this->assertSame(
+                [$expectedDates[$placement->value]],
+                $this->formattedDates($dates),
+            );
+        }
+    }
 
     public function test_it_distributes_even_and_single_day_schedules(): void
     {

backend/tests/Unit/Schedule/UseCases/CreateScheduleTest.php

@@ -156,7 +156,7 @@ class CreateScheduleTest extends TestCase
         );
     }
 
-    public function test_it_spreads_sparse_work_across_the_full_range(): void
+    public function test_it_defaults_sparse_work_to_spread_across_the_full_range(): void
     {
         $user = $this->user();
         $setRepository = new FakeSetRepository;
@@ -192,7 +192,7 @@ class CreateScheduleTest extends TestCase
             levelId: $lessonLevel->getId(),
             startDate: '2026-08-10',
             targetDate: '2026-08-16',
-            workloadPlacement: 'middle',
+            workloadPlacement: null,
         ));
 
         $this->assertSame(