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Tree Helpers

Tree inspection is one of the most useful parts of the testing package because it turns a visual hierarchy into something you can query and assert against directly.

Query APIs

  • Avalonia.HeadlessTestingFramework.VisualTreeTestHelper: visual-tree traversal helpers
  • Avalonia.HeadlessTestingFramework.LogicalTreeTestHelper: logical-tree traversal helpers
  • Avalonia.HeadlessTestingFramework.ControlFinder: fluent control-finding API
  • Avalonia.HeadlessTestingFramework.TreeXPath: XPath-like queries for tree traversal

These are a good fit when test code needs to locate controls by type, name, class, property, or relative position.

Assertion APIs

  • Avalonia.HeadlessTestingFramework.TreeValidator: declarative validation rules and summary output
  • Avalonia.HeadlessTestingFramework.TreeComparer: snapshot and diff workflows for visual or logical trees
  • Avalonia.HeadlessTestingFramework.TemplateComparer: template-part and template-structure verification

Example validator usage:

window.Validate()
    .RequireName("ZoomBorder")
    .RequireType<Canvas>()
    .AssertValid();

When To Use Which

  • Use ControlFinder for ergonomic queries in everyday tests.
  • Use TreeXPath when selector-style queries are easier to read than chained calls.
  • Use TreeValidator when you need a small ruleset with strong failure messages.
  • Use TreeComparer or TemplateComparer when regression detection matters more than imperative assertions.