diff --git a/Tests/AppKit/CPViewThemeChangeTest.j b/Tests/AppKit/CPViewThemeChangeTest.j
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+++ b/Tests/AppKit/CPViewThemeChangeTest.j
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+/*
+ *  CPViewThemeChangeTest.j
+ *  AppKit
+ *
+ *  Created by David Richardson on 31/10/2026.
+ *  Copyright David Richardson 2026.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+@import <AppKit/AppKit.j>
+
+/*
+    A view resolves each theme attribute from its own values, then its theme, then its
+    class default. When any of these changes, the view must resolve the new value and
+    lay itself out again. These tests build small themes in code, so they depend on no
+    real theme.
+*/
+
+@implementation _CPThemeChangeView : CPView
+{
+    int     layoutCount @accessors;
+    int     themeChangeCount @accessors;
+    int     displayRequestCount @accessors;
+}
+
++ (CPString)defaultThemeClass
+{
+    return @"theme-change-view";
+}
+
++ (CPDictionary)themeAttributes
+{
+    return @{
+        @"accent": @"class default",
+        @"margin": @"class default"
+    };
+}
+
+- (void)layoutSubviews
+{
+    layoutCount++;
+}
+
+/*
+    needsDisplay is true only for a view with its own drawRect:, so the request is
+    recorded here.
+*/
+- (void)setNeedsDisplay:(BOOL)aFlag
+{
+    if (aFlag)
+        displayRequestCount++;
+
+    [super setNeedsDisplay:aFlag];
+}
+
+- (void)objectDidChangeTheme
+{
+    themeChangeCount++;
+
+    [super objectDidChangeTheme];
+}
+
+@end
+
+@implementation CPViewThemeChangeTest : OJTestCase
+{
+    CPTheme                 firstTheme;
+    CPTheme                 secondTheme;
+    CPTheme                 defaultTheme;
+    _CPThemeChangeView      view;
+}
+
+- (void)setUp
+{
+    // This will init the global var CPApp which are used internally in the AppKit
+    [[CPApplication alloc] init];
+
+    defaultTheme = [CPTheme defaultTheme];
+    firstTheme = [self themeNamed:@"theme-change-first" themeClass:nil accent:@"first"];
+    secondTheme = [self themeNamed:@"theme-change-second" themeClass:nil accent:@"second"];
+    view = [self newView];
+
+    [view setTheme:firstTheme];
+    [_CPDisplayServer run];
+    [view setLayoutCount:0];
+    [view setThemeChangeCount:0];
+}
+
+- (void)tearDown
+{
+    [CPTheme setDefaultTheme:defaultTheme];
+}
+
+- (_CPThemeChangeView)newView
+{
+    return [[_CPThemeChangeView alloc] initWithFrame:CGRectMake(0.0, 0.0, 100.0, 100.0)];
+}
+
+- (CPTheme)themeNamed:(CPString)aName themeClass:(CPString)aThemeClass accent:(CPString)anAccent
+{
+    var theme = [[CPTheme alloc] initWithName:aName],
+        template = [self newView];
+
+    if (aThemeClass)
+        [template setThemeClass:aThemeClass];
+
+    [template setValue:anAccent forThemeAttribute:@"accent"];
+    [theme takeThemeFromObject:template];
+
+    return theme;
+}
+
+- (id)archived:(CPView)aView
+{
+    return [CPKeyedUnarchiver unarchiveObjectWithData:[CPKeyedArchiver archivedDataWithRootObject:aView]];
+}
+
+- (void)assertAccent:(CPString)aValue ofView:(CPView)aView
+{
+    [self assert:aValue equals:[aView currentValueForThemeAttribute:@"accent"]];
+}
+
+- (void)testAViewResolvesItsThemeValue
+{
+    [self assertAccent:@"first" ofView:view];
+}
+
+- (void)testAnAttributeTheThemeDoesNotDefineUsesTheClassDefault
+{
+    [self assert:@"class default" equals:[view currentValueForThemeAttribute:@"margin"]];
+}
+
+- (void)testAViewWithoutAThemeUsesTheClassDefault
+{
+    [view setTheme:nil];
+
+    [self assertAccent:@"class default" ofView:view];
+}
+
+- (void)testSettingAThemeChangesTheResolvedValue
+{
+    [view setTheme:secondTheme];
+
+    [self assertAccent:@"second" ofView:view];
+}
+
+- (void)testSettingAThemeNotifiesTheView
+{
+    [view setTheme:secondTheme];
+
+    [self assert:1 equals:[view themeChangeCount]];
+}
+
+- (void)testSettingTheSameThemeDoesNothing
+{
+    [view setTheme:firstTheme];
+
+    [self assert:0 equals:[view themeChangeCount]];
+}
+
+- (void)testSettingAThemeQueuesLayout
+{
+    [view setTheme:secondTheme];
+    [_CPDisplayServer run];
+
+    [self assert:1 equals:[view layoutCount]];
+}
+
+- (void)testSettingAThemeRequestsDisplay
+{
+    [view setDisplayRequestCount:0];
+    [view setTheme:secondTheme];
+
+    [self assertTrue:[view displayRequestCount] > 0];
+}
+
+- (void)testAThemeChangeReachesNestedViews
+{
+    var parent = [self newView],
+        child = [self newView],
+        grandchild = [self newView];
+
+    [parent addSubview:child];
+    [child addSubview:grandchild];
+    [parent _setThemeIncludingDescendants:secondTheme];
+
+    [self assertAccent:@"second" ofView:parent];
+    [self assertAccent:@"second" ofView:child];
+    [self assertAccent:@"second" ofView:grandchild];
+}
+
+- (void)testAPerViewValueTakesPriorityOverTheTheme
+{
+    [view setValue:@"own" forThemeAttribute:@"accent"];
+
+    [self assertAccent:@"own" ofView:view];
+}
+
+- (void)testAPerViewValueSurvivesAThemeChange
+{
+    [view setValue:@"own" forThemeAttribute:@"accent"];
+    [view setTheme:secondTheme];
+
+    [self assertAccent:@"own" ofView:view];
+}
+
+- (void)testAPerViewValueQueuesLayout
+{
+    [view setValue:@"own" forThemeAttribute:@"accent"];
+    [_CPDisplayServer run];
+
+    [self assert:1 equals:[view layoutCount]];
+}
+
+- (void)testSettingTheSamePerViewValueQueuesNoLayout
+{
+    [view setValue:@"first" forThemeAttribute:@"accent"];
+    [_CPDisplayServer run];
+
+    [self assert:0 equals:[view layoutCount]];
+}
+
+- (void)testAStateSelectsItsValue
+{
+    [view setValue:@"disabled" forThemeAttribute:@"accent" inState:CPThemeStateDisabled];
+    [self assertAccent:@"first" ofView:view];
+
+    [view setThemeState:CPThemeStateDisabled];
+    [self assertAccent:@"disabled" ofView:view];
+
+    [view unsetThemeState:CPThemeStateDisabled];
+    [self assertAccent:@"first" ofView:view];
+}
+
+- (void)testAStateChangeQueuesLayout
+{
+    [view setThemeState:CPThemeStateDisabled];
+    [_CPDisplayServer run];
+
+    [self assert:1 equals:[view layoutCount]];
+}
+
+- (void)testSettingAThemeClassChangesTheResolvedValue
+{
+    var theme = [self themeNamed:@"theme-change-class" themeClass:@"other-class" accent:@"other class"];
+
+    [view setTheme:theme];
+    [view setThemeClass:@"other-class"];
+
+    [self assertAccent:@"other class" ofView:view];
+}
+
+- (void)testSettingAThemeClassQueuesLayout
+{
+    [view setThemeClass:@"other-class"];
+    [_CPDisplayServer run];
+
+    [self assert:1 equals:[view layoutCount]];
+}
+
+- (void)testANewViewUsesTheDefaultTheme
+{
+    [CPTheme setDefaultTheme:secondTheme];
+
+    [self assertAccent:@"second" ofView:[self newView]];
+}
+
+- (void)testChangingTheDefaultThemeLeavesAnExistingViewUnchanged
+{
+    [CPTheme setDefaultTheme:secondTheme];
+
+    [self assertAccent:@"first" ofView:view];
+}
+
+- (void)testADecodedViewUsesTheDefaultTheme
+{
+    [CPTheme setDefaultTheme:secondTheme];
+
+    [self assertAccent:@"second" ofView:[self archived:view]];
+}
+
+- (void)testADecodedViewKeepsAPerViewValue
+{
+    [view setValue:@"own" forThemeAttribute:@"accent"];
+
+    [self assertAccent:@"own" ofView:[self archived:view]];
+}
+
+- (void)testADecodedViewKeepsAPerViewStateValue
+{
+    [view setValue:@"disabled" forThemeAttribute:@"accent" inState:CPThemeStateDisabled];
+
+    var decoded = [self archived:view];
+
+    [decoded setThemeState:CPThemeStateDisabled];
+
+    [self assertAccent:@"disabled" ofView:decoded];
+}
+
+- (void)testADecodedViewKeepsItsThemeState
+{
+    [view setThemeState:CPThemeStateDisabled];
+
+    [self assertTrue:[[self archived:view] hasThemeState:CPThemeStateDisabled]];
+}
+
+- (void)testADecodedViewKeepsItsThemeClass
+{
+    [view setThemeClass:@"other-class"];
+
+    [self assert:@"other-class" equals:[[self archived:view] themeClass]];
+}
+
+@end