Added unit tests for low-coverage System.Windows.Forms classes by Sathish-087 · Pull Request #14911 · dotnet/winforms

Sathish-087 · 2026-08-20T11:33:18Z

Fixes #13442

Proposed changes

Added 9 unit tests for RadioButtonFlatAdapter.
Added 11 unit tests for RadioButtonPopupAdapter.
Added 8 unit tests for ToolStrip.RestoreFocusMessageFilter.
Added 8 unit tests for HtmlHistory.
Covered paint operations (PaintUp, PaintDown, PaintOver) for radio button adapter implementations.
Added coverage for adapter creation and layout behavior validation.
Added tests for DPI-aware check size calculations and shadowed text behavior.
Added coverage for checked-state rendering and text/image rendering scenarios.
Added tests validating focus restoration and message filtering behavior in ToolStrip.RestoreFocusMessageFilter.
Added tests covering HtmlHistory navigation APIs (Back, Forward, Go), property accessors, argument validation, and disposal behavior.
Improved unit test coverage for low-coverage classes in the System.Windows.Forms namespace.

Customer Impact

Improves unit test coverage for several previously low-coverage System.Windows.Forms classes.
Increases confidence in rendering, layout, focus restoration, and HTML history navigation functionality.
Helps prevent regressions in public and protected virtual APIs across the tested components.

Regression?

No

Risk

Low (tests only, no product code changes)

Test methodology

Executed existing WinForms unit test suite.
Added and executed new unit tests for RadioButtonFlatAdapter.
Added and executed new unit tests for RadioButtonPopupAdapter.
Added and executed new unit tests for ToolStrip.RestoreFocusMessageFilter.
Added and executed new unit tests for HtmlHistory.

Accessibility testing

NA

Test environment(s)

Visual Studio (Test Explorer)
Windows
.NET 11

Microsoft Reviewers: Open in CodeFlow

KlausLoeffelmann · 2026-08-31T16:03:56Z

@SimonZhao888, could you do a manual review of this? Thx!

Copilot

🟡 Changes recommended

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Pull request overview

Adds unit coverage for previously low-coverage WinForms rendering, focus-restoration, and browser-history components.

Changes:

Tests radio-button adapter painting and layout.
Tests ToolStrip focus restoration.
Tests HtmlHistory navigation, validation, and disposal.

File summaries

File	Description
`RadioButtonFlatAdapterTests.cs`	Tests flat adapter rendering and layout.
`RadioButtonPopupAdapterTests.cs`	Tests popup adapter states and rendering.
`ToolStrip.RestoreFocusMessageFilterTests.cs`	Tests message filtering and focus restoration.
`HtmlHistoryTests.cs`	Tests history APIs and disposal behavior.

Review details

Files reviewed: 4/4 changed files
Comments generated: 3
Review effort level: Balanced

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Sathish-087 · 2026-09-07T09:30:08Z

+
+        Action action = () => adapter.PaintDown(e, control.Checked ? CheckState.Checked : CheckState.Unchecked);
+
+        action.Should().NotThrow();


Updated the paint test cases based on existing "HasPixelChanged" pattern.

Sathish-087 · 2026-09-07T09:30:15Z

+
+        Action action = () => adapter.PaintDown(e, control.Checked ? CheckState.Checked : CheckState.Unchecked);
+
+        action.Should().NotThrow();


Updated the paint test cases based on existing HasPixelChanged pattern.

Sathish-087 · 2026-09-07T09:30:44Z

+            await Task.Run(() => control.Navigate(path));
+            Assert.True(await source.Task);


Modified this test case

SimonZhao888 · 2026-09-01T06:54:07Z

+        history.Should().NotBeNull();
+
+        // Relative position always forwards to COM go(); 0 is the safe relative position.
+        Action goRelative = () => history!.Go(0);


It would make our test cases more comprehensive if we could also cover some edge-case navigation scenarios here—such as Go(-1) or cases where the index falls outside the range of available history.

Added new test case for Go(-1).

codecov · 2026-09-07T09:50:01Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37.24166%. Comparing base (1616b0c) to head (6a2cfc6).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##                main      #14911   +/-   ##
=============================================
  Coverage   37.24166%   37.24166%           
=============================================
  Files            246         246           
  Lines           9774        9774           
  Branches        1029        1029           
=============================================
  Hits            3640        3640           
  Misses          5970        5970           
  Partials         164         164

Flag	Coverage Δ
Debug	`37.24166% <ø> (ø)`
production	`39.36526% <ø> (ø)`
test	`20.64923% <ø> (ø)`
unit	`39.36526% <ø> (ø)`

Flags with carried forward coverage won't be shown. Click here to find out more.

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…ix_Issue_13442

Sathish-087 and others added 2 commits August 12, 2026 09:44

Added unit test cases for Issue 13442

a12e78c

Merge branch 'dotnet:main' into Fix_Issue_13442

a7b347c

Sathish-087 requested a review from a team as a code owner August 20, 2026 11:33

dotnet-policy-service Bot assigned Sathish-087 Aug 20, 2026

KlausLoeffelmann requested review from SimonZhao888 and a balanced review from Copilot August 31, 2026 16:04

KlausLoeffelmann added this to the 11.0-rc2 milestone Aug 31, 2026

Copilot started reviewing on behalf of KlausLoeffelmann August 31, 2026 16:05 View session

Copilot AI reviewed Aug 31, 2026

View reviewed changes

SimonZhao888 reviewed Sep 1, 2026

View reviewed changes

Address review comments

e6a3d2f

Merge branch 'main' of https://github.com/Sathish-087/winforms into F…

6a2cfc6

…ix_Issue_13442

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		Action action = () => adapter.PaintDown(e, control.Checked ? CheckState.Checked : CheckState.Unchecked);

		action.Should().NotThrow();

		await Task.Run(() => control.Navigate(path));
		Assert.True(await source.Task);

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Proposed changes

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Accessibility testing

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Sathish-087 commented Aug 20, 2026 •

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