diff --git a/tests/Elastic.Documentation.Tests/Testing/NavigationDumpTests.cs b/tests/Elastic.Documentation.Tests/Testing/NavigationDumpTests.cs
new file mode 100644
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+++ b/tests/Elastic.Documentation.Tests/Testing/NavigationDumpTests.cs
@@ -0,0 +1,119 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using AwesomeAssertions;
+using Elastic.Documentation.Navigation;
+using Elastic.Documentation.Testing;
+using Nullean.Snapshots;
+
+namespace Elastic.Documentation.Tests.Testing;
+
+/// <summary>
+/// Navigation.Tests snapshots <see cref="NavigationDump.ToText"/>, so a bug here would be accepted into every one of those snapshots.
+/// In particular a broken <c>[wrong parent]</c> check would hide the regression it exists to catch.
+/// </summary>
+public class NavigationDumpTests
+{
+	[Test]
+	public void ToText_ListsTheIndexFirstThenTheChildren_IndentedByDepth_WithFlagsAndTrimmedTypeNames()
+	{
+		var island = new FakeNode("/docs/island", "Island", "Island index") { IsIsland = true };
+		var root = new FakeNode("/docs", "Docs", "Docs index");
+		root.Add(new FakeLeaf("/docs/a", "A"));
+		root.Add(new FakeLeaf("/docs/b", "B") { Hidden = true });
+		root.Add(island);
+		island.Add(new FakeGenericLeaf<string>("/docs/island/x", "X"));
+
+		NavigationDump
+			.ToText(root)
+			.Should()
+			.MatchInlineSnapshot(
+				"""
+			FakeNode  /docs  "Docs"
+			  index: FakeLeaf  /docs  "Docs index"
+			  FakeLeaf  /docs/a  "A"
+			  FakeLeaf  /docs/b  "B" [hidden]
+			  FakeNode  /docs/island  "Island" [island]
+			    index: FakeLeaf  /docs/island  "Island index"
+			    FakeGenericLeaf  /docs/island/x  "X"
+			"""
+			);
+	}
+
+	[Test]
+	public void ToText_ChildWhoseParentIsAnotherNode_IsFlaggedWrongParent()
+	{
+		var other = new FakeNode("/docs/other", "Other", "Other index");
+		var root = new FakeNode("/docs", "Docs", "Docs index");
+		root.Add(new FakeLeaf("/docs/fine", "Fine"));
+		// listed under root, but it points back at another node
+		root.Add(new FakeLeaf("/docs/stray", "Stray"), parent: other);
+		root.Add(other);
+
+		NavigationDump
+			.ToText(root)
+			.Should()
+			.MatchInlineSnapshot(
+				"""
+			FakeNode  /docs  "Docs"
+			  index: FakeLeaf  /docs  "Docs index"
+			  FakeLeaf  /docs/fine  "Fine"
+			  FakeLeaf  /docs/stray  "Stray" [wrong parent]
+			  FakeNode  /docs/other  "Other"
+			    index: FakeLeaf  /docs/other  "Other index"
+			"""
+			);
+	}
+
+	[Test]
+	public void ToText_IndexPage_IsNotCheckedForItsParent()
+	{
+		// a virtual file's index has a different parent than its node, so it must not be flagged
+		var root = new FakeNode("/docs", "Docs", "Docs index");
+		root.Index.Parent = new FakeNode("/elsewhere", "Elsewhere", "Elsewhere index");
+
+		NavigationDump
+			.ToText(root)
+			.Should()
+			.MatchInlineSnapshot("""
+			FakeNode  /docs  "Docs"
+			  index: FakeLeaf  /docs  "Docs index"
+			""");
+	}
+
+	private sealed class FakeModel : INavigationModel;
+
+	private class FakeLeaf(string url, string title) : ILeafNavigationItem<INavigationModel>
+	{
+		public string Url { get; } = url;
+		public string NavigationTitle { get; } = title;
+		public IRootNavigationItem<INavigationModel, INavigationItem> NavigationRoot => null!;
+		public INodeNavigationItem<INavigationModel, INavigationItem>? Parent { get; set; }
+		public bool Hidden { get; init; }
+		public bool IsIsland { get; init; }
+		public int NavigationIndex { get; set; }
+		public INavigationModel Model { get; } = new FakeModel();
+	}
+
+	private sealed class FakeGenericLeaf<T>(string url, string title) : FakeLeaf(url, title);
+
+	private sealed class FakeNode : FakeLeaf, INodeNavigationItem<INavigationModel, INavigationItem>
+	{
+		private readonly List<INavigationItem> _children = [];
+
+		public FakeNode(string url, string title, string indexTitle) : base(url, title) =>
+			Index = new FakeLeaf(url, indexTitle) { Parent = null };
+
+		public string Id => Url;
+		public FakeLeaf Index { get; }
+		ILeafNavigationItem<INavigationModel> INodeNavigationItem<INavigationModel, INavigationItem>.Index => Index;
+		public IReadOnlyCollection<INavigationItem> NavigationItems => _children;
+
+		public void Add(FakeLeaf child, INodeNavigationItem<INavigationModel, INavigationItem>? parent = null)
+		{
+			child.Parent = parent ?? this;
+			_children.Add(child);
+		}
+	}
+}