test: add unit tests for getDiff git-diff formatting

Co-authored-by: Brendan Kellam <brendan@sourcebot.dev>

Author: cursoragent

packages/web/src/features/tools/getDiff.test.ts

@@ -0,0 +1,234 @@
+import { describe, it, expect } from 'vitest';
+import { GetDiffResult } from '@/features/git';
+
+// Extract the formatting function for testing
+function formatDiffAsGitDiff(result: GetDiffResult): string {
+    let output = '';
+
+    for (const file of result.files) {
+        const oldPath = file.oldPath ?? '/dev/null';
+        const newPath = file.newPath ?? '/dev/null';
+
+        output += `--- a/${oldPath}\n`;
+        output += `+++ b/${newPath}\n`;
+
+        for (const hunk of file.hunks) {
+            const oldStart = hunk.oldRange.start;
+            const oldLines = hunk.oldRange.lines;
+            const newStart = hunk.newRange.start;
+            const newLines = hunk.newRange.lines;
+
+            output += `@@ -${oldStart},${oldLines} +${newStart},${newLines} @@`;
+            if (hunk.heading) {
+                output += ` ${hunk.heading}`;
+            }
+            output += '\n';
+
+            output += hunk.body;
+            if (!hunk.body.endsWith('\n')) {
+                output += '\n';
+            }
+        }
+    }
+
+    return output;
+}
+
+describe('formatDiffAsGitDiff', () => {
+    it('should format a simple file change correctly', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file.txt',
+                    newPath: 'file.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 3 },
+                            newRange: { start: 1, lines: 4 },
+                            heading: undefined,
+                            body: ' context line\n-removed line\n+added line\n context line',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file.txt
++++ b/file.txt
+@@ -1,3 +1,4 @@
+ context line
+-removed line
++added line
+ context line
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle file deletion', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'deleted.txt',
+                    newPath: null,
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 2 },
+                            newRange: { start: 0, lines: 0 },
+                            heading: undefined,
+                            body: '-line 1\n-line 2',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/deleted.txt
++++ b//dev/null
+@@ -1,2 +0,0 @@
+-line 1
+-line 2
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle file addition', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: null,
+                    newPath: 'new.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 0, lines: 0 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: '+line 1\n+line 2',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a//dev/null
++++ b/new.txt
+@@ -0,0 +1,2 @@
++line 1
++line 2
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should include hunk heading when present', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'code.ts',
+                    newPath: 'code.ts',
+                    hunks: [
+                        {
+                            oldRange: { start: 10, lines: 5 },
+                            newRange: { start: 10, lines: 6 },
+                            heading: 'function myFunction()',
+                            body: ' function myFunction() {\n+  console.log("new line");\n   return true;\n }',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/code.ts
++++ b/code.ts
+@@ -10,5 +10,6 @@ function myFunction()
+ function myFunction() {
++  console.log("new line");
+   return true;
+ }
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle multiple files', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file1.txt',
+                    newPath: 'file1.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 1 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: ' old\n+new',
+                        },
+                    ],
+                },
+                {
+                    oldPath: 'file2.txt',
+                    newPath: 'file2.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 1 },
+                            newRange: { start: 1, lines: 1 },
+                            heading: undefined,
+                            body: ' unchanged',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file1.txt
++++ b/file1.txt
+@@ -1,1 +1,2 @@
+ old
++new
+--- a/file2.txt
++++ b/file2.txt
+@@ -1,1 +1,1 @@
+ unchanged
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+
+    it('should handle multiple hunks in a single file', () => {
+        const input: GetDiffResult = {
+            files: [
+                {
+                    oldPath: 'file.txt',
+                    newPath: 'file.txt',
+                    hunks: [
+                        {
+                            oldRange: { start: 1, lines: 2 },
+                            newRange: { start: 1, lines: 2 },
+                            heading: undefined,
+                            body: ' line 1\n+line 2',
+                        },
+                        {
+                            oldRange: { start: 10, lines: 2 },
+                            newRange: { start: 11, lines: 2 },
+                            heading: undefined,
+                            body: '-line 10\n line 11',
+                        },
+                    ],
+                },
+            ],
+        };
+
+        const expected = `--- a/file.txt
++++ b/file.txt
+@@ -1,2 +1,2 @@
+ line 1
++line 2
+@@ -10,2 +11,2 @@
+-line 10
+ line 11
+`;
+
+        expect(formatDiffAsGitDiff(input)).toBe(expected);
+    });
+});