Improve code coverage for cli package (#13724)

packages/cli/src/ui/utils/ui-sizing.test.ts

@@ -0,0 +1,71 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import { calculateMainAreaWidth } from './ui-sizing.js';
+import { type LoadedSettings } from '../../config/settings.js';
+
+// Mock dependencies
+const mocks = vi.hoisted(() => ({
+  isAlternateBufferEnabled: vi.fn(),
+}));
+
+vi.mock('../hooks/useAlternateBuffer.js', () => ({
+  isAlternateBufferEnabled: mocks.isAlternateBufferEnabled,
+}));
+
+describe('ui-sizing', () => {
+  const createSettings = (useFullWidth?: boolean): LoadedSettings =>
+    ({
+      merged: {
+        ui: {
+          useFullWidth,
+        },
+      },
+    }) as unknown as LoadedSettings;
+
+  describe('calculateMainAreaWidth', () => {
+    it.each([
+      // width, useFullWidth, alternateBuffer, expected
+      [80, true, false, 80],
+      [100, true, false, 100],
+      [80, true, true, 79], // -1 for alternate buffer
+      [100, true, true, 99],
+
+      // Default behavior (useFullWidth undefined or true)
+      [100, undefined, false, 100],
+
+      // useFullWidth: false (Smart sizing)
+      [80, false, false, 78], // 98% of 80
+      [132, false, false, 119], // 90% of 132
+      [200, false, false, 180], // 90% of 200 (>= 132)
+
+      // Interpolation check
+      [106, false, false, 100], // Approx middle
+    ])(
+      'should return %i when width=%i, useFullWidth=%s, altBuffer=%s',
+      (width, useFullWidth, altBuffer, expected) => {
+        mocks.isAlternateBufferEnabled.mockReturnValue(altBuffer);
+        const settings = createSettings(useFullWidth);
+
+        expect(calculateMainAreaWidth(width, settings)).toBe(expected);
+      },
+    );
+
+    it('should match snapshot for interpolation range', () => {
+      mocks.isAlternateBufferEnabled.mockReturnValue(false);
+      const settings = createSettings(false);
+
+      const results: Record<number, number> = {};
+      // Test range from 80 to 132
+      for (let w = 80; w <= 132; w += 4) {
+        results[w] = calculateMainAreaWidth(w, settings);
+      }
+
+      expect(results).toMatchSnapshot();
+    });
+  });
+});