feat(gradebook): wire keepHighest through backend for keep-N feature

- Permit keepHighest in update_weights_params
- Parse keepHighest from request and pass to bulk_update via keep_highest
- Echo keepHighest in serialize_weight_updates response
- Serialize keepHighest from contribution in index.json.jbuilder
- Add controller tests: round-trip persist and index response
- Add model tests: bulk_update persists keep_highest in equal mode

Author: LWS49

app/controllers/course/gradebook_controller.rb

@@ -47,6 +47,7 @@ def parse_weight_entry(entry)
       tab_id: entry[:tabId].to_i,
       weight: entry[:weight].to_f,
       weight_mode: entry[:weightMode] || 'equal',
+      keep_highest: entry[:keepHighest].to_i,
       excluded_assessment_ids: (entry[:excludedAssessmentIds] || []).map(&:to_i),
       assessment_weights: (entry[:assessmentWeights] || []).map do |aw|
         { assessment_id: aw[:assessmentId].to_i, weight: aw[:weight].to_f }
@@ -56,14 +57,15 @@ def parse_weight_entry(entry)
 
   def update_weights_params
     params.permit(
-      weights: [:tabId, :weight, :weightMode,
+      weights: [:tabId, :weight, :weightMode, :keepHighest,
                 excludedAssessmentIds: [], assessmentWeights: [:assessmentId, :weight]]
     )
   end
 
   def serialize_weight_updates(updates)
     updates.map do |u|
       entry = { tabId: u[:tab_id], weight: u[:weight], weightMode: u[:weight_mode].to_s,
+                keepHighest: u[:keep_highest],
                 excludedAssessmentIds: u[:excluded_assessment_ids] }
       if u[:weight_mode].to_s == 'custom'
         entry[:assessmentWeights] = u[:assessment_weights].map do |aw|

app/views/course/gradebook/index.json.jbuilder

@@ -15,6 +15,7 @@ json.tabs @tabs do |tab|
     contribution = @tab_contributions[tab.id]
     json.gradebookWeight (contribution&.weight || 0).to_f
     json.weightMode(contribution&.weight_mode || 'equal')
+    json.keepHighest(contribution&.keep_highest || 0)
   end
 end
 

client/app/bundles/course/gradebook/__tests__/ConfigureWeightsPrompt.test.tsx

@@ -147,6 +147,7 @@ describe('<ConfigureWeightsPrompt />', () => {
           tabId: 10,
           weight: 50,
           weightMode: 'custom',
+          keepHighest: 0,
           excludedAssessmentIds: [],
           assessmentWeights: [
             { assessmentId: 101, weight: 25 },
@@ -157,6 +158,7 @@ describe('<ConfigureWeightsPrompt />', () => {
           tabId: 11,
           weight: 50,
           weightMode: 'equal',
+          keepHighest: 0,
           excludedAssessmentIds: [],
         },
       ]);
@@ -404,6 +406,7 @@ describe('per-assessment exclusion', () => {
     expect(arg[0]).toMatchObject({
       tabId: 10,
       weight: 50,
+      keepHighest: 0,
       excludedAssessmentIds: [101, 102],
     });
   });
@@ -477,4 +480,168 @@ describe('per-assessment exclusion', () => {
       expect(screen.queryByText(/no weights set yet/i)).not.toBeInTheDocument();
     });
   });
+
+  it('shows assessment weights sum footer in custom mode', () => {
+    setup();
+    fireEvent.click(
+      within(modeGroup('Assignments')).getByRole('radio', { name: /custom/i }),
+    );
+    // Expand to see the footer
+    // custom mode auto-expands, so just check the footer
+    expect(screen.getByText(/Assessment weights:/i)).toBeInTheDocument();
+  });
+});
+
+describe('per-assessment exclusion (extended)', () => {
+  beforeEach(() => jest.clearAllMocks());
+
+  it('shows "Excluded" label in custom mode for excluded assessment', async () => {
+    setup({
+      assessments: [
+        {
+          id: 101,
+          title: A1,
+          tabId: 10,
+          maxGrade: 100,
+          gradebookExcluded: true,
+        },
+        { id: 102, title: A2, tabId: 10, maxGrade: 50 },
+      ],
+      tabs: [
+        {
+          id: 10,
+          title: 'Assignments',
+          categoryId: 1,
+          gradebookWeight: 50,
+          weightMode: 'custom',
+        },
+      ],
+    });
+    fireEvent.click(screen.getAllByRole('button', { name: '' })[0]);
+    expect(await screen.findByText('Excluded')).toBeInTheDocument();
+  });
+
+  it('does not show "Excluded" label in equal mode for excluded assessment', async () => {
+    setup({
+      assessments: [
+        {
+          id: 101,
+          title: A1,
+          tabId: 10,
+          maxGrade: 100,
+          gradebookExcluded: true,
+        },
+        { id: 102, title: A2, tabId: 10, maxGrade: 50 },
+      ],
+    });
+    fireEvent.click(screen.getAllByRole('button', { name: '' })[0]);
+    // In equal mode excluded shows "Excluded" text too
+    expect(await screen.findByText('Excluded')).toBeInTheDocument();
+  });
+});
+
+describe('keep-highest control', () => {
+  const TOGGLE = 'Enable keep highest for Assignments';
+  const INPUT = 'Keep highest for Assignments';
+  const three = [
+    { id: 101, title: A1, tabId: 10, maxGrade: 100 },
+    { id: 102, title: A2, tabId: 10, maxGrade: 50 },
+    { id: 103, title: 'Assignment 3', tabId: 10, maxGrade: 80 },
+  ];
+
+  beforeEach(() => jest.clearAllMocks());
+
+  it('renders a keep-highest checkbox; number field hidden until checked', () => {
+    setup({ assessments: three });
+    expect(screen.getByRole('checkbox', { name: TOGGLE })).toBeInTheDocument();
+    expect(screen.queryByRole('spinbutton', { name: INPUT })).not.toBeInTheDocument();
+    fireEvent.click(screen.getByRole('checkbox', { name: TOGGLE }));
+    expect(screen.getByRole('spinbutton', { name: INPUT })).toBeInTheDocument();
+  });
+
+  it('shows a visible "Keep highest" text label next to the checkbox', () => {
+    setup({ assessments: three });
+    expect(screen.getByText('Keep highest')).toBeInTheDocument();
+  });
+
+  it('defaults the count to included − 1 when checked', () => {
+    setup({ assessments: three }); // 3 assessments -> default to 2
+    fireEvent.click(screen.getByRole('checkbox', { name: TOGGLE }));
+    expect(screen.getByRole('spinbutton', { name: INPUT })).toHaveValue(2);
+  });
+
+  it('hides checkbox + field in custom mode', () => {
+    setup({ assessments: three });
+    fireEvent.click(
+      within(modeGroup('Assignments')).getByRole('radio', { name: /custom/i }),
+    );
+    expect(screen.queryByRole('checkbox', { name: TOGGLE })).not.toBeInTheDocument();
+    expect(screen.queryByRole('spinbutton', { name: INPUT })).not.toBeInTheDocument();
+  });
+
+  it('seeds the field (checkbox pre-checked) from tab.keepHighest', () => {
+    setup({
+      assessments: three,
+      tabs: [
+        { id: 10, title: 'Assignments', categoryId: 1, gradebookWeight: 50, keepHighest: 2 },
+        { id: 11, title: 'Optional', categoryId: 1, gradebookWeight: 50 },
+      ],
+    });
+    expect(screen.getByRole('checkbox', { name: TOGGLE })).toBeChecked();
+    expect(screen.getByRole('spinbutton', { name: INPUT })).toHaveValue(2);
+  });
+
+  it('disables the checkbox when only one assessment is included', () => {
+    setup({
+      assessments: [{ id: 101, title: A1, tabId: 10, maxGrade: 100 }],
+    });
+    expect(screen.getByRole('checkbox', { name: TOGGLE })).toBeDisabled();
+  });
+
+  it('sends keepHighest in the save payload', async () => {
+    setup({ assessments: three });
+    fireEvent.click(screen.getByRole('checkbox', { name: TOGGLE }));
+    fireEvent.click(screen.getByRole('button', { name: /save/i }));
+    await waitFor(() =>
+      expect(operations.updateGradebookWeights).toHaveBeenCalled(),
+    );
+    const arg = (operations.updateGradebookWeights as jest.Mock).mock.calls[0][0];
+    const tab10 = arg.find((e: { tabId: number }) => e.tabId === 10);
+    expect(tab10.keepHighest).toBe(2);
+  });
+
+  it('unchecking sends keepHighest 0', async () => {
+    setup({
+      assessments: three,
+      tabs: [
+        { id: 10, title: 'Assignments', categoryId: 1, gradebookWeight: 50, keepHighest: 2 },
+        { id: 11, title: 'Optional', categoryId: 1, gradebookWeight: 50 },
+      ],
+    });
+    // checkbox is pre-checked; uncheck it
+    fireEvent.click(screen.getByRole('checkbox', { name: TOGGLE }));
+    fireEvent.click(screen.getByRole('button', { name: /save/i }));
+    await waitFor(() =>
+      expect(operations.updateGradebookWeights).toHaveBeenCalled(),
+    );
+    const arg = (operations.updateGradebookWeights as jest.Mock).mock.calls[0][0];
+    const tab10 = arg.find((e: { tabId: number }) => e.tabId === 10);
+    expect(tab10.keepHighest).toBe(0);
+  });
+
+  it('blocks saving on non-integer input but not on keep > included (overflow)', async () => {
+    setup({ assessments: three });
+    fireEvent.click(screen.getByRole('checkbox', { name: TOGGLE }));
+    const input = screen.getByRole('spinbutton', { name: INPUT });
+
+    // overflow: keep=5 > included=3 -> warning but save NOT blocked
+    fireEvent.change(input, { target: { value: '5' } });
+    expect(screen.getByRole('button', { name: /save/i })).not.toBeDisabled();
+    expect(screen.getByText(/keeps more assessments than it contains/i)).toBeInTheDocument();
+
+    // non-integer (0): should block saving
+    fireEvent.change(input, { target: { value: '0' } });
+    expect(screen.getByRole('button', { name: /save/i })).toBeDisabled();
+    expect(screen.getByText(/keep at least 1/i)).toBeInTheDocument();
+  });
 });

client/app/bundles/course/gradebook/__tests__/GradebookWeightedTable.test.tsx

@@ -1212,4 +1212,49 @@ describe('GradebookWeightedTable', () => {
       }
     });
   });
+
+  describe('drop-lowest breakdown marker', () => {
+    // One equal tab, keepHighest=1, three graded assessments. The lowest (a1) drops.
+    const dropConfig = {
+      tabs: [{ ...makeTab(10, 'Missions', 1, 60), keepHighest: 1 }],
+      assessments: [
+        makeAssessment(1, 'Mission 1', 10, 100),
+        makeAssessment(2, 'Mission 2', 10, 100),
+        makeAssessment(3, 'Mission 3', 10, 100),
+      ],
+      students: [makeStudent(1, 'Alice')],
+      submissions: [makeSub(1, 1, 30), makeSub(1, 2, 60), makeSub(1, 3, 90)],
+    };
+
+    it('labels the dropped assessment "Dropped (lowest)" (not "Excluded")', async () => {
+      const user = userEvent.setup();
+      renderWeighted(dropConfig);
+      await user.click(screen.getByRole('button', { name: /expand Alice/i }));
+      const detail = await screen.findByTestId(breakdownRowId(1, 10, 1));
+      expect(
+        within(detail).getByText(/Dropped \(lowest\)/),
+      ).toBeInTheDocument();
+      expect(within(detail).queryByText(/Excluded/i)).not.toBeInTheDocument();
+    });
+
+    it('shows 0 (not —) in the dropped assessment cell in points mode', async () => {
+      const user = userEvent.setup();
+      renderWeighted(dropConfig);
+      await user.click(screen.getByRole('button', { name: /expand Alice/i }));
+      const detail = await screen.findByTestId(breakdownRowId(1, 10, 1));
+      // Dropped contributes 0 points — distinct from excluded's em dash.
+      expect(within(detail).getByText('0')).toBeInTheDocument();
+      expect(within(detail).queryByText('—')).not.toBeInTheDocument();
+    });
+
+    it("shows the dropped assessment's own grade % in percentage mode", async () => {
+      const user = userEvent.setup();
+      renderWeighted(dropConfig);
+      await user.click(screen.getByRole('radio', { name: /percentage/i }));
+      await user.click(screen.getByRole('button', { name: /expand Alice/i }));
+      const detail = await screen.findByTestId(breakdownRowId(1, 10, 1));
+      // a1 = 30/100 = 30% — visible so the instructor sees the dropped grade.
+      expect(within(detail).getByText('30%')).toBeInTheDocument();
+    });
+  });
 });