From 21161e4afead7e684a008f4c3f1a76f818ddddbc Mon Sep 17 00:00:00 2001
From: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>
Date: Wed, 12 Aug 2026 22:01:56 +0300
Subject: [PATCH] test(export): add unit tests for canvas image export
 functionality (#85)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
---
 src/ui/export.test.ts | 171 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)
 create mode 100644 src/ui/export.test.ts

diff --git a/src/ui/export.test.ts b/src/ui/export.test.ts
new file mode 100644
index 0000000..d3009ef
--- /dev/null
+++ b/src/ui/export.test.ts
@@ -0,0 +1,171 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { exportSheetImage } from './export';
+import { writeImageFile } from '../storage';
+
+vi.mock('../storage', () => ({
+  writeImageFile: vi.fn(),
+}));
+
+describe('exportSheetImage', () => {
+  let mockContext2D: any;
+  let mockCanvas: any;
+  let toastMock: any;
+  let tMock: any;
+
+  beforeEach(() => {
+    toastMock = vi.fn();
+    tMock = vi.fn((key: string) => `trans_${key}`);
+
+    mockContext2D = {
+      measureText: vi.fn().mockReturnValue({ width: 10 }),
+      scale: vi.fn(),
+      fillRect: vi.fn(),
+      fillText: vi.fn(),
+      font: '',
+      fillStyle: '',
+    };
+
+    mockCanvas = {
+      getContext: vi.fn().mockReturnValue(mockContext2D),
+      toBlob: vi.fn((cb) => cb(new Blob(['fake-image-data'], { type: 'image/png' }))),
+      width: 0,
+      height: 0,
+    };
+
+    vi.stubGlobal('document', {
+      documentElement: {},
+      createElement: vi.fn((tag) => {
+        if (tag === 'canvas') return mockCanvas;
+        return {};
+      })
+    });
+
+    vi.stubGlobal('window', {
+      devicePixelRatio: 0
+    });
+
+    vi.stubGlobal('getComputedStyle', vi.fn().mockReturnValue({
+      getPropertyValue: vi.fn((prop) => {
+        if (prop === '--bg') return '';
+        if (prop === '--fg') return '';
+        if (prop === '--result') return '';
+        if (prop === '--mono') return '';
+        return '';
+      })
+    }));
+
+    vi.stubGlobal('Blob', class Blob {
+      content: any[];
+      options: any;
+      constructor(content: any[], options: any) {
+        this.content = content;
+        this.options = options;
+      }
+      async arrayBuffer() {
+        return new Uint8Array([1, 2, 3]).buffer;
+      }
+    });
+
+    vi.stubGlobal('ClipboardItem', class ClipboardItem {
+      constructor(data: any) {
+        Object.assign(this, data);
+      }
+    });
+
+    vi.stubGlobal('navigator', {
+      clipboard: {
+        write: vi.fn().mockResolvedValue(undefined)
+      }
+    });
+
+    vi.stubGlobal('btoa', (str: string) => Buffer.from(str, 'binary').toString('base64'));
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+    vi.clearAllMocks();
+  });
+
+  it('should create a canvas and copy it to clipboard successfully', async () => {
+    await exportSheetImage({
+      lines: ['1 + 1'],
+      results: [{ text: '2' }],
+      fontSize: 14,
+      toast: toastMock,
+      t: tMock
+    });
+
+    expect(document.createElement).toHaveBeenCalledWith('canvas');
+    expect(mockCanvas.getContext).toHaveBeenCalledWith('2d');
+    expect(mockContext2D.fillText).toHaveBeenCalledWith('1 + 1', expect.any(Number), expect.any(Number));
+    expect(mockContext2D.fillText).toHaveBeenCalledWith('2', expect.any(Number), expect.any(Number));
+
+    expect(navigator.clipboard.write).toHaveBeenCalled();
+    expect(toastMock).toHaveBeenCalledWith('trans_imageCopied');
+  });
+
+  it('should handle blob failure', async () => {
+    mockCanvas.toBlob = vi.fn((cb) => cb(null));
+
+    await exportSheetImage({
+      lines: ['test'],
+      results: [{ text: null }],
+      fontSize: 14,
+      toast: toastMock,
+      t: tMock
+    });
+
+    expect(toastMock).toHaveBeenCalledWith('trans_imageFailed');
+    expect(navigator.clipboard.write).not.toHaveBeenCalled();
+  });
+
+  it('should fallback to writeImageFile when clipboard write fails', async () => {
+    navigator.clipboard.write = vi.fn().mockRejectedValue(new Error('clipboard fail'));
+    vi.mocked(writeImageFile).mockResolvedValue(true);
+
+    await exportSheetImage({
+      lines: ['fallback'],
+      results: [{ text: 'res' }],
+      fontSize: 14,
+      toast: toastMock,
+      t: tMock
+    });
+
+    expect(navigator.clipboard.write).toHaveBeenCalled();
+    expect(writeImageFile).toHaveBeenCalled();
+    expect(writeImageFile).toHaveBeenCalledWith('AQID');
+    expect(toastMock).toHaveBeenCalledWith('trans_saved');
+  });
+
+  it('should handle writeImageFile failure in fallback', async () => {
+    navigator.clipboard.write = vi.fn().mockRejectedValue(new Error('clipboard fail'));
+    vi.mocked(writeImageFile).mockRejectedValue(new Error('save fail'));
+
+    await exportSheetImage({
+      lines: ['fail'],
+      results: [{ text: 'res' }],
+      fontSize: 14,
+      toast: toastMock,
+      t: tMock
+    });
+
+    expect(writeImageFile).toHaveBeenCalled();
+    expect(toastMock).toHaveBeenCalledWith('trans_imageFailed');
+  });
+
+  it('should handle writeImageFile returning false', async () => {
+    navigator.clipboard.write = vi.fn().mockRejectedValue(new Error('clipboard fail'));
+    vi.mocked(writeImageFile).mockResolvedValue(false);
+
+    await exportSheetImage({
+      lines: ['fail'],
+      results: [{ text: 'res' }],
+      fontSize: 14,
+      toast: toastMock,
+      t: tMock
+    });
+
+    expect(writeImageFile).toHaveBeenCalled();
+    expect(toastMock).not.toHaveBeenCalledWith('trans_saved');
+  });
+});