diff --git a/src/browser/tests/selection.html b/src/browser/tests/selection.html
new file mode 100644
index 00000000..ceae479f
--- /dev/null
+++ b/src/browser/tests/selection.html
@@ -0,0 +1,408 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<script src="./testing.js"></script>
+
+<div id="test-content">
+  <p id="p1">The quick brown fox</p>
+  <p id="p2">jumps over the lazy dog</p>
+  <div id="nested">
+    <span id="s1">Hello</span>
+    <span id="s2">World</span>
+  </div>
+</div>
+
+<script id=basic>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    testing.expectEqual(0, sel.rangeCount);
+    testing.expectEqual("None", sel.type);
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(null, sel.anchorNode);
+    testing.expectEqual(null, sel.focusNode);
+    testing.expectEqual(0, sel.anchorOffset);
+    testing.expectEqual(0, sel.focusOffset);
+    testing.expectEqual("none", sel.direction);
+  }
+</script>
+
+<script id=collapse>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    // Collapse to a position
+    sel.collapse(textNode, 4);
+    
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual("Caret", sel.type);
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(textNode, sel.anchorNode);
+    testing.expectEqual(textNode, sel.focusNode);
+    testing.expectEqual(4, sel.anchorOffset);
+    testing.expectEqual(4, sel.focusOffset);
+    testing.expectEqual("none", sel.direction);
+    
+    // Collapse to null removes all ranges
+    sel.collapse(null);
+    testing.expectEqual(0, sel.rangeCount);
+    testing.expectEqual("None", sel.type);
+  }
+</script>
+
+<script id=setPosition>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    const p2 = document.getElementById("p2");
+    const textNode = p2.firstChild;
+    
+    // setPosition is an alias for collapse
+    sel.setPosition(textNode, 10);
+    
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual("Caret", sel.type);
+    testing.expectEqual(textNode, sel.anchorNode);
+    testing.expectEqual(10, sel.anchorOffset);
+    
+    // Test default offset
+    sel.setPosition(textNode);
+    testing.expectEqual(0, sel.anchorOffset);
+    
+    // Test null
+    sel.setPosition(null);
+    testing.expectEqual(0, sel.rangeCount);
+  }
+</script>
+
+<script id=addRange>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    const range1 = document.createRange();
+    const p1 = document.getElementById("p1");
+    range1.selectNodeContents(p1);
+    
+    sel.addRange(range1);
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual("Range", sel.type);
+    testing.expectEqual(false, sel.isCollapsed);
+    
+    // Adding same range again should do nothing
+    sel.addRange(range1);
+    testing.expectEqual(1, sel.rangeCount);
+    
+    // Adding different range
+    const range2 = document.createRange();
+    const p2 = document.getElementById("p2");
+    range2.selectNodeContents(p2);
+    
+    sel.addRange(range2);
+    testing.expectEqual(2, sel.rangeCount);
+  }
+</script>
+
+<script id=getRangeAt>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    const range = document.createRange();
+    const p1 = document.getElementById("p1");
+    range.selectNodeContents(p1);
+    sel.addRange(range);
+    
+    const retrieved = sel.getRangeAt(0);
+    testing.expectEqual(range, retrieved);
+  }
+</script>
+
+<script id=removeRange>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    const range1 = document.createRange();
+    const range2 = document.createRange();
+    const p1 = document.getElementById("p1");
+    const p2 = document.getElementById("p2");
+    
+    range1.selectNodeContents(p1);
+    range2.selectNodeContents(p2);
+    
+    sel.addRange(range1);
+    sel.addRange(range2);
+    testing.expectEqual(2, sel.rangeCount);
+    
+    sel.removeRange(range1);
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual(range2, sel.getRangeAt(0));
+    
+    // Removing non-existent range does nothing
+    sel.removeRange(range1);
+    testing.expectEqual(1, sel.rangeCount);
+  }
+</script>
+
+<script id=removeAllRanges>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+
+    const range1 = document.createRange();
+    const range2 = document.createRange();
+    
+    range1.selectNodeContents(document.getElementById("p1"));
+    range2.selectNodeContents(document.getElementById("p2"));
+    
+    sel.addRange(range1);
+    sel.addRange(range2);
+    testing.expectEqual(2, sel.rangeCount);
+    
+    sel.removeAllRanges();
+    testing.expectEqual(0, sel.rangeCount);
+    testing.expectEqual("none", sel.direction);
+  }
+</script>
+
+<script id=empty>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    const range = document.createRange();
+    range.selectNodeContents(document.getElementById("p1"));
+    
+    sel.addRange(range);
+    testing.expectEqual(1, sel.rangeCount);
+    
+    // empty() is an alias for removeAllRanges()
+    sel.empty();
+    testing.expectEqual(0, sel.rangeCount);
+  }
+</script>
+
+<script id=collapseToStart>
+  {
+    const sel = window.getSelection();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    const range = document.createRange();
+    range.setStart(textNode, 4);
+    range.setEnd(textNode, 15);
+    
+    sel.removeAllRanges();
+    sel.addRange(range);
+    
+    testing.expectEqual(false, sel.isCollapsed);
+    testing.expectEqual(4, sel.anchorOffset);
+    testing.expectEqual(15, sel.focusOffset);
+    
+    sel.collapseToStart();
+    
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual(textNode, sel.anchorNode);
+    testing.expectEqual(4, sel.anchorOffset);
+    testing.expectEqual(4, sel.focusOffset);
+    testing.expectEqual("none", sel.direction);
+  }
+</script>
+
+<script id=collapseToEnd>
+  {
+    const sel = window.getSelection();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    const range = document.createRange();
+    range.setStart(textNode, 4);
+    range.setEnd(textNode, 15);
+    
+    sel.removeAllRanges();
+    sel.addRange(range);
+    
+    testing.expectEqual(false, sel.isCollapsed);
+    
+    sel.collapseToEnd();
+    
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(1, sel.rangeCount);
+    testing.expectEqual(textNode, sel.anchorNode);
+    testing.expectEqual(15, sel.anchorOffset);
+    testing.expectEqual(15, sel.focusOffset);
+    testing.expectEqual("none", sel.direction);
+  }
+</script>
+
+<script id=extend>
+  {
+    const sel = window.getSelection();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    // Start with collapsed selection
+    sel.collapse(textNode, 10);
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(10, sel.anchorOffset);
+    testing.expectEqual("none", sel.direction);
+    
+    // Extend forward
+    sel.extend(textNode, 15);
+    testing.expectEqual(false, sel.isCollapsed);
+    testing.expectEqual(10, sel.anchorOffset);
+    testing.expectEqual(15, sel.focusOffset);
+    testing.expectEqual("forward", sel.direction);
+    
+    // Extend backward from anchor
+    sel.extend(textNode, 5);
+    testing.expectEqual(false, sel.isCollapsed);
+    testing.expectEqual(10, sel.anchorOffset);
+    testing.expectEqual(5, sel.focusOffset);
+    testing.expectEqual("backward", sel.direction);
+    
+    // Extend to same position as anchor
+    sel.extend(textNode, 10);
+    testing.expectEqual(true, sel.isCollapsed);
+    testing.expectEqual(10, sel.anchorOffset);
+    testing.expectEqual(10, sel.focusOffset);
+    testing.expectEqual("forward", sel.direction);
+  }
+</script>
+
+<script id=direction>
+  {
+    const sel = window.getSelection();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    // Forward selection
+    sel.collapse(textNode, 5);
+    sel.extend(textNode, 10);
+    testing.expectEqual("forward", sel.direction);
+    testing.expectEqual(5, sel.anchorOffset);
+    testing.expectEqual(10, sel.focusOffset);
+    
+    // Backward selection
+    sel.collapse(textNode, 10);
+    sel.extend(textNode, 5);
+    testing.expectEqual("backward", sel.direction);
+    testing.expectEqual(10, sel.anchorOffset);
+    testing.expectEqual(5, sel.focusOffset);
+    
+    // None (collapsed)
+    sel.collapse(textNode, 7);
+    testing.expectEqual("none", sel.direction);
+  }
+</script>
+
+<script id=containsNode>
+  {
+    const sel = window.getSelection();
+    const nested = document.getElementById("nested");
+    const s1 = document.getElementById("s1");
+    const s2 = document.getElementById("s2");
+    
+    const range = document.createRange();
+    range.selectNodeContents(nested);
+    
+    sel.removeAllRanges();
+    sel.addRange(range);
+    
+    // Full containment (default)
+    testing.expectEqual(true, sel.containsNode(s1, false));
+    testing.expectEqual(true, sel.containsNode(s2, false));
+    testing.expectEqual(false, sel.containsNode(nested, false));
+    
+    // Partial containment
+    testing.expectEqual(true, sel.containsNode(s1, true));
+    testing.expectEqual(true, sel.containsNode(s2, true));
+    testing.expectEqual(true, sel.containsNode(nested, true));
+    
+    // Node outside selection
+    const p1 = document.getElementById("p1");
+    testing.expectEqual(false, sel.containsNode(p1, false));
+    testing.expectEqual(false, sel.containsNode(p1, true));
+  }
+</script>
+
+
+<script id=deleteFromDocument>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    const originalText = textNode.textContent;
+    
+    const range = document.createRange();
+    range.setStart(textNode, 4);
+    range.setEnd(textNode, 15);
+    
+    sel.removeAllRanges();
+    sel.addRange(range);
+    
+    sel.deleteFromDocument();
+    
+    // Text should be deleted
+    const expectedText = originalText.slice(0, 4) + originalText.slice(15);
+    testing.expectEqual(expectedText, textNode.textContent);
+    
+    // Selection should be collapsed at deletion point
+    testing.expectEqual(true, sel.isCollapsed);
+    
+    // Restore original text for other tests
+    textNode.textContent = originalText;
+  }
+</script>
+
+<script id=multipleRanges>
+  {
+    const sel = window.getSelection();
+    sel.removeAllRanges();
+    
+    const p1 = document.getElementById("p1");
+    const p2 = document.getElementById("p2");
+    
+    const range1 = document.createRange();
+    const range2 = document.createRange();
+    
+    range1.selectNodeContents(p1);
+    range2.selectNodeContents(p2);
+    
+    sel.addRange(range1);
+    sel.addRange(range2);
+    
+    testing.expectEqual(2, sel.rangeCount);
+    
+    testing.expectEqual(p1, sel.anchorNode);
+    testing.expectEqual(p2, sel.focusNode);
+    testing.expectEqual(0, sel.anchorOffset);
+    testing.expectEqual(p2.childNodes.length, sel.focusOffset);
+  }
+</script>
+
+<script id=typeProperty>
+  {
+    const sel = window.getSelection();
+    const p1 = document.getElementById("p1");
+    const textNode = p1.firstChild;
+    
+    // None type
+    sel.removeAllRanges();
+    testing.expectEqual("None", sel.type);
+    
+    // Caret type (collapsed)
+    sel.collapse(textNode, 5);
+    testing.expectEqual("Caret", sel.type);
+    
+    // Range type (not collapsed)
+    sel.extend(textNode, 10);
+    testing.expectEqual("Range", sel.type);
+  }
+</script>
