Add comprehensive test coverage for core transformation functions

- Add tests for convert-deepnote-block-type-to-jupyter.ts (100% coverage)
- Add tests for convert-deepnote-block-to-jupyter-cell.ts (100% coverage)
- Add tests for transform-deepnote-yaml-to-notebook-content.ts (100% coverage)

This increases overall test coverage from 26.57% to 55.94%, providing
comprehensive testing for the core Deepnote-to-Jupyter transformation logic.

Author: devin-ai-integration[bot]

src/__tests__/convert-deepnote-block-to-jupyter-cell.spec.ts

@@ -0,0 +1,293 @@
+// Copyright (c) Deepnote
+// Distributed under the terms of the Modified BSD License.
+
+import { convertDeepnoteBlockToJupyterCell } from '../convert-deepnote-block-to-jupyter-cell';
+import { DeepnoteBlock } from '@deepnote/blocks';
+
+jest.mock('@deepnote/blocks', () => ({
+  createPythonCode: jest.fn((block: any) => block.source || 'print("test")'),
+  createMarkdown: jest.fn((block: any) => block.source || '# Test')
+}));
+
+jest.mock('../convert-deepnote-block-type-to-jupyter', () => ({
+  convertDeepnoteBlockTypeToJupyter: jest.fn((type: string) => {
+    if (
+      [
+        'code',
+        'sql',
+        'notebook-function',
+        'big-number',
+        'visualization',
+        'input-text',
+        'input-checkbox',
+        'input-textarea',
+        'input-file',
+        'input-select',
+        'input-date-range',
+        'input-date',
+        'input-slider'
+      ].includes(type)
+    ) {
+      return 'code';
+    }
+    return 'markdown';
+  })
+}));
+
+describe('convertDeepnoteBlockToJupyterCell', () => {
+  describe('code cells', () => {
+    it('should convert a basic code block to a Jupyter code cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-1',
+        type: 'code',
+        source: 'print("hello")',
+        metadata: { foo: 'bar' }
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+      expect(result.metadata).toEqual({ foo: 'bar', cell_id: 'block-1' });
+      expect(result.source).toBe('print("hello")');
+      expect(result.execution_count).toBeNull();
+      expect(result.outputs).toEqual([]);
+    });
+
+    it('should include execution count if present', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-2',
+        type: 'code',
+        source: 'x = 1',
+        metadata: {},
+        executionCount: 5
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+      expect(result.execution_count).toBe(5);
+    });
+
+    it('should include outputs if present', () => {
+      const blockOutputs = [
+        {
+          output_type: 'stream',
+          name: 'stdout',
+          text: 'hello\n'
+        }
+      ];
+
+      const block: DeepnoteBlock = {
+        id: 'block-3',
+        type: 'code',
+        source: 'print("hello")',
+        metadata: {},
+        outputs: blockOutputs
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+      expect(result.outputs).toEqual(blockOutputs);
+    });
+
+    it('should remove truncated property from outputs', () => {
+      const blockOutputs = [
+        {
+          output_type: 'stream',
+          name: 'stdout',
+          text: 'hello\n',
+          truncated: true
+        }
+      ];
+
+      const block: DeepnoteBlock = {
+        id: 'block-4',
+        type: 'code',
+        source: 'print("hello")',
+        metadata: {},
+        outputs: blockOutputs
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+      expect(result.outputs).toHaveLength(1);
+      const resultOutputs = result.outputs as any[];
+      expect(resultOutputs[0]).not.toHaveProperty('truncated');
+      expect(resultOutputs[0]).toEqual({
+        output_type: 'stream',
+        name: 'stdout',
+        text: 'hello\n'
+      });
+    });
+
+    it('should handle multiple outputs with truncated properties', () => {
+      const blockOutputs = [
+        {
+          output_type: 'stream',
+          name: 'stdout',
+          text: 'line1\n',
+          truncated: true
+        },
+        {
+          output_type: 'stream',
+          name: 'stdout',
+          text: 'line2\n',
+          truncated: false
+        }
+      ];
+
+      const block: DeepnoteBlock = {
+        id: 'block-5',
+        type: 'code',
+        source: 'print("test")',
+        metadata: {},
+        outputs: blockOutputs
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+      expect(result.outputs).toHaveLength(2);
+      const resultOutputs = result.outputs as any[];
+      expect(resultOutputs[0]).not.toHaveProperty('truncated');
+      expect(resultOutputs[1]).not.toHaveProperty('truncated');
+    });
+
+    it('should not mutate the original block', () => {
+      const blockOutputs = [
+        {
+          output_type: 'stream',
+          name: 'stdout',
+          text: 'hello\n',
+          truncated: true
+        }
+      ];
+
+      const block: DeepnoteBlock = {
+        id: 'block-6',
+        type: 'code',
+        source: 'print("hello")',
+        metadata: { test: 'value' },
+        outputs: blockOutputs
+      } as any;
+
+      convertDeepnoteBlockToJupyterCell(block);
+
+      expect(block.outputs![0]).toHaveProperty('truncated');
+      expect(block.metadata).toEqual({ test: 'value' });
+    });
+  });
+
+  describe('markdown cells', () => {
+    it('should convert a basic markdown block to a Jupyter markdown cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-7',
+        type: 'markdown',
+        source: '# Hello',
+        metadata: { foo: 'bar' }
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('markdown');
+      expect(result.metadata).toEqual({});
+      expect(result.source).toBe('# Hello');
+    });
+
+    it('should convert text-cell-h1 to markdown cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-8',
+        type: 'text-cell-h1',
+        source: 'Heading 1',
+        metadata: {}
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('markdown');
+    });
+
+    it('should convert image block to markdown cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-9',
+        type: 'image',
+        source: '![alt](url)',
+        metadata: {}
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('markdown');
+    });
+
+    it('should not include metadata from Deepnote block in markdown cells', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-10',
+        type: 'markdown',
+        source: 'Text',
+        metadata: { deepnoteMetadata: 'should not appear' }
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('markdown');
+      expect(result.metadata).toEqual({});
+    });
+  });
+
+  describe('special block types', () => {
+    it('should convert sql block to code cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-11',
+        type: 'sql',
+        source: 'SELECT * FROM table',
+        metadata: {}
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+    });
+
+    it('should convert visualization block to code cell', () => {
+      const block: DeepnoteBlock = {
+        id: 'block-12',
+        type: 'visualization',
+        source: 'chart_data',
+        metadata: {}
+      } as any;
+
+      const result = convertDeepnoteBlockToJupyterCell(block);
+
+      expect(result.cell_type).toBe('code');
+    });
+
+    it('should convert input blocks to code cells', () => {
+      const inputTypes = [
+        'input-text',
+        'input-checkbox',
+        'input-textarea',
+        'input-file',
+        'input-select',
+        'input-date-range',
+        'input-date',
+        'input-slider'
+      ];
+
+      inputTypes.forEach(type => {
+        const block: DeepnoteBlock = {
+          id: `block-${type}`,
+          type,
+          source: 'input_value',
+          metadata: {}
+        } as any;
+
+        const result = convertDeepnoteBlockToJupyterCell(block);
+
+        expect(result.cell_type).toBe('code');
+      });
+    });
+  });
+});