Step 107: add diff preview view

editor/tests/step107_test.cpp

@@ -0,0 +1,27 @@
+// Step 107 TDD Test: Diff view utilities
+//
+// Tests:
+// 1. buildLineDiff marks changed lines on both sides
+
+#include <cassert>
+#include <iostream>
+#include "DiffUtils.h"
+
+int main() {
+    int passed = 0;
+    int failed = 0;
+
+    std::string before = "a\nb\nc";
+    std::string after = "a\nx\nc\nd";
+    auto diff = buildLineDiff(before, after);
+    assert(diff.beforeLines.size() == 1);
+    assert(diff.beforeLines[0] == 1);
+    assert(diff.afterLines.size() == 2);
+    assert(diff.afterLines[0] == 1);
+    assert(diff.afterLines[1] == 3);
+    std::cout << "Test 1 PASS: diff lines detected" << std::endl;
+    ++passed;
+
+    std::cout << "\n=== Step 107 Results: " << passed << " passed, " << failed << " failed ===" << std::endl;
+    return failed > 0 ? 1 : 0;
+}