diff --git a/core/modules/system/tests/themes/test_theme_depending_nonexisting_module/test_theme_depending_on_nonexisting_module.info.yml b/core/modules/system/tests/themes/test_theme_depending_nonexisting_module/test_theme_depending_on_nonexisting_module.info.yml
index 2499fc444c..43c8ed477b 100644
--- a/core/modules/system/tests/themes/test_theme_depending_nonexisting_module/test_theme_depending_on_nonexisting_module.info.yml
+++ b/core/modules/system/tests/themes/test_theme_depending_nonexisting_module/test_theme_depending_on_nonexisting_module.info.yml
@@ -1,4 +1,4 @@
-name: test theme depending on nonexisting module
+name: Test Theme Depending on Nonexisting Module
 type: theme
 core: 8.x
 base theme: stark
diff --git a/core/modules/system/tests/themes/test_theme_depending_on_modules/test_module_required_by_theme/test_module_required_by_theme.info.yml b/core/modules/system/tests/themes/test_theme_depending_on_modules/test_module_required_by_theme/test_module_required_by_theme.info.yml
index 9d402c7c1d..75fcd17ae5 100644
--- a/core/modules/system/tests/themes/test_theme_depending_on_modules/test_module_required_by_theme/test_module_required_by_theme.info.yml
+++ b/core/modules/system/tests/themes/test_theme_depending_on_modules/test_module_required_by_theme/test_module_required_by_theme.info.yml
@@ -1,4 +1,4 @@
-name: test module required by theme
+name: Test Module Required by Theme
 type: module
 core: 8.x
 package: Testing
diff --git a/core/modules/system/tests/themes/test_theme_depending_on_modules/test_theme_depending_on_modules.info.yml b/core/modules/system/tests/themes/test_theme_depending_on_modules/test_theme_depending_on_modules.info.yml
index 7edd71f3b8..a20675c742 100644
--- a/core/modules/system/tests/themes/test_theme_depending_on_modules/test_theme_depending_on_modules.info.yml
+++ b/core/modules/system/tests/themes/test_theme_depending_on_modules/test_theme_depending_on_modules.info.yml
@@ -1,4 +1,4 @@
-name: test theme depending on modules
+name: Test Theme Depending on Modules
 type: theme
 core: 8.x
 base theme: stark
diff --git a/core/modules/system/tests/themes/test_theme_with_a_base_theme_depending_on_modules/test_theme_with_a_base_theme_depending_on_modules.info.yml b/core/modules/system/tests/themes/test_theme_with_a_base_theme_depending_on_modules/test_theme_with_a_base_theme_depending_on_modules.info.yml
index 4653fbf941..91391fdac8 100644
--- a/core/modules/system/tests/themes/test_theme_with_a_base_theme_depending_on_modules/test_theme_with_a_base_theme_depending_on_modules.info.yml
+++ b/core/modules/system/tests/themes/test_theme_with_a_base_theme_depending_on_modules/test_theme_with_a_base_theme_depending_on_modules.info.yml
@@ -1,4 +1,4 @@
-name: test theme with a base theme depending on modules
+name: Test Theme with a Base Theme Depending on Modules
 type: theme
 core: 8.x
 base theme: test_theme_depending_on_modules
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
index 068af6744c..e0027056be 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
@@ -106,21 +106,11 @@ public function testInstallSubTheme() {
    */
   public function testInstallNonExisting() {
     $name = 'non_existing_theme';
-
-    $themes = $this->themeHandler()->listInfo();
-    $this->assertEmpty(array_keys($themes));
-
-    try {
-      $message = 'ThemeInstaller::install() throws UnknownExtensionException upon installing a non-existing theme.';
-      $this->themeInstaller()->install([$name]);
-      $this->fail($message);
-    }
-    catch (UnknownExtensionException $e) {
-      $this->pass(get_class($e) . ': ' . $e->getMessage());
-    }
-
     $themes = $this->themeHandler()->listInfo();
     $this->assertEmpty(array_keys($themes));
+    $this->expectException(UnknownExtensionException::class);
+    $this->expectExceptionMessage('Unknown themes: non_existing_theme.');
+    $this->themeInstaller()->install([$name]);
   }
 
   /**
@@ -144,15 +134,11 @@ public function testInstallNameTooLong() {
    */
   public function testInstallThemeWithUnmetModuleDependencies() {
     $name = 'test_theme_depending_on_modules';
-
-    try {
-      $message = 'ThemeInstaller::install() throws MissingDependencyException upon installing a theme with unmet module dependencies.';
-      $this->themeInstaller()->install([$name]);
-      $this->fail($message);
-    }
-    catch (MissingDependencyException $e) {
-      $this->pass(get_class($e) . ': ' . $e->getMessage());
-    }
+    $themes = $this->themeHandler()->listInfo();
+    $this->assertEmpty(array_keys($themes));
+    $this->expectException(MissingDependencyException::class);
+    $this->expectExceptionMessage('Unable to install theme: \'test_theme_depending_on_modules\' due to missing module dependencies: \'test_module_required_by_theme, test_another_module_required_by_theme.');
+    $this->themeInstaller()->install([$name]);
   }
 
   /**
@@ -166,16 +152,9 @@ public function testInstallThemeWithMetModuleDependencies() {
     $this->themeInstaller()->install([$name]);
     $themes = $this->themeHandler()->listInfo();
     $this->assertTrue(isset($themes[$name]));
-
-    // Confirm that modules that active themes depend on can't be uninstalled.
-    try {
-      $message = 'Attempting to uninstall a module that an active theme depends on results in a ModuleUninstallValidatorException';
-      $this->container->get('module_installer')->uninstall(['test_module_required_by_theme']);
-      $this->fail($message);
-    }
-    catch (ModuleUninstallValidatorException $e) {
-      $this->pass(get_class($e) . ': ' . $e->getMessage());
-    }
+    $this->expectException(ModuleUninstallValidatorException::class);
+    $this->expectExceptionMessage('The following reasons prevent the modules from being uninstalled: Required by the theme: Test Theme Depending on Modules');
+    $this->container->get('module_installer')->uninstall(['test_module_required_by_theme']);
   }
 
   /**