diff -u b/core/modules/update/src/ProjectCoreCompatibility.php b/core/modules/update/src/ProjectCoreCompatibility.php
--- b/core/modules/update/src/ProjectCoreCompatibility.php
+++ b/core/modules/update/src/ProjectCoreCompatibility.php
@@ -139,7 +139,8 @@
     foreach ($releases_to_set as &$release) {
       if (!empty($release['core_compatibility'])) {
         $release['core_compatible'] = $this->isCoreCompatible($release['core_compatibility']);
-        $release['core_compatibility_details'] = $this->createCoreCompatibilityDetails($release['core_compatibility'], $release['core_compatible']);
+        $release['core_compatibility_range'] = $this->createMessageFromCoreCompatibility($release['core_compatibility']);
+        $release['core_compatibility_details'] = $this->createCoreCompatibilityDetails($release['core_compatible'], $release['core_compatibility_range']);
       }
     }
   }
@@ -147,21 +148,24 @@
   /**
    * Creates core a compatibility details element.
    *
-   * @param string $core_compatibility_constraint
-   *   A semantic version constraint.
    * @param bool $core_compatible
    *   Is the release compatible with the currently installed version of core?
+   * @param string $core_compatibility_range
+   *   The translated core compatibility range message from
+   *   static::createMessageFromCoreCompatibility().
    *
    * @return array
    *   Render array of the core compatibility details element.
    *
    * @todo Should this be a twig template?
+   *
+   * @see static::createMessageFromCoreCompatibility()
    */
-  protected function createCoreCompatibilityDetails($core_compatibility_constraint, $core_compatible) {
+  protected function createCoreCompatibilityDetails($core_compatible, $core_compatibility_range) {
     $element = [
       '#type' => 'details',
       'compatibility_range' => [
-        '#markup' => $this->createMessageFromCoreCompatibility($core_compatibility_constraint),
+        '#markup' => $core_compatibility_range,
       ],
     ];
     if ($core_compatible) {
only in patch2:
unchanged:
--- a/core/drupalci.yml
+++ b/core/drupalci.yml
@@ -21,37 +21,37 @@ build:
       # deprecated code.
       run_tests.phpunit:
         types: 'PHPUnit-Unit'
-        testgroups: '--all'
+        testgroups: '--module update'
         suppress-deprecations: false
         halt-on-fail: false
       run_tests.kernel:
         types: 'PHPUnit-Kernel'
-        testgroups: '--all'
-        suppress-deprecations: false
-        halt-on-fail: false
-      run_tests.simpletest:
-         types: 'Simpletest'
-         testgroups: '--all'
-         suppress-deprecations: false
-         halt-on-fail: false
-      run_tests.build:
-        # Limit concurrency due to disk space concerns.
-        concurrency: 15
-        types: 'PHPUnit-Build'
-        testgroups: '--all'
+        testgroups: '--module update'
         suppress-deprecations: false
         halt-on-fail: false
+#      run_tests.simpletest:
+#         types: 'Simpletest'
+#         testgroups: '--all'
+#         suppress-deprecations: false
+#         halt-on-fail: false
+#      run_tests.build:
+#        # Limit concurrency due to disk space concerns.
+#        concurrency: 15
+#        types: 'PHPUnit-Build'
+#        testgroups: '--all'
+#        suppress-deprecations: false
+#        halt-on-fail: false
       run_tests.functional:
         types: 'PHPUnit-Functional'
-        testgroups: '--all'
-        suppress-deprecations: false
-        halt-on-fail: false
-      run_tests.javascript:
-        concurrency: 15
-        types: 'PHPUnit-FunctionalJavascript'
-        testgroups: '--all'
+        testgroups: '--module update'
         suppress-deprecations: false
         halt-on-fail: false
+#      run_tests.javascript:
+#        concurrency: 15
+#        types: 'PHPUnit-FunctionalJavascript'
+#        testgroups: '--all'
+#        suppress-deprecations: false
+#        halt-on-fail: false
       # Run nightwatch testing.
       # @see https://www.drupal.org/project/drupal/issues/2869825
-      nightwatchjs:
+#      nightwatchjs:
only in patch2:
unchanged:
--- a/core/modules/update/tests/src/Unit/ProjectCoreCompatibilityTest.php
+++ b/core/modules/update/tests/src/Unit/ProjectCoreCompatibilityTest.php
@@ -20,6 +20,14 @@ public function testSetProjectCoreCompatibilityRanges(array $project_data, $core
     $project_compatibility = new ProjectCoreCompatibility($core_data, $core_releases);
     $project_compatibility->setStringTranslation($this->getStringTranslationStub());
     $project_compatibility->setReleaseMessage($project_data);
+    // Ignore the <details> markup, and only assert that the core compatibility
+    // constraint, range message and core compatible boolean matches.
+    $purge_compatibility_details = function($release) {
+      unset($release['core_compatibility_details']);
+      return $release;
+    };
+    $project_data['releases'] = array_map($purge_compatibility_details, $project_data['releases']);
+    $project_data['security updates'] = array_map($purge_compatibility_details, $project_data['security updates']);
     $this->assertSame($expected_releases, $project_data['releases']);
     $this->assertSame($expected_security_updates, $project_data['security updates']);
   }
@@ -72,22 +80,26 @@ public function providerSetProjectCoreCompatibilityRanges() {
       'expected_releases' => [
         '1.0.1' => [
           'core_compatibility' => '8.x',
-          'core_compatibility_message' => 'This module is compatible with Drupal core: 8.8.0 to 8.9.2',
+          'core_compatible' => TRUE,
+          'core_compatibility_range' => 'Requires Drupal core: 8.8.0 to 8.9.2',
         ],
         '1.2.3' => [
           'core_compatibility' => '^8.9 || ^9',
-          'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.0 to 8.9.2',
+          'core_compatible' => FALSE,
+          'core_compatibility_range' => 'Requires Drupal core: 8.9.0 to 8.9.2',
         ],
         '1.2.4' => [
           'core_compatibility' => '^8.9.2 || ^9',
-          'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.2',
+          'core_compatible' => FALSE,
+          'core_compatibility_range' => 'Requires Drupal core: 8.9.2',
         ],
         '1.2.6' => [],
       ],
       'expected_security_updates' => [
         '1.2.5' => [
           'core_compatibility' => '8.9.0 || 8.9.2 || ^9.0.1',
-          'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.0, 8.9.2',
+          'core_compatible' => FALSE,
+          'core_compatibility_range' => 'Requires Drupal core: 8.9.0, 8.9.2',
         ],
       ],
     ];
@@ -110,22 +122,26 @@ public function providerSetProjectCoreCompatibilityRanges() {
     $test_cases['with 9 full releases']['expected_releases'] = [
       '1.0.1' => [
         'core_compatibility' => '8.x',
-        'core_compatibility_message' => 'This module is compatible with Drupal core: 8.8.0 to 8.9.2',
+        'core_compatible' => TRUE,
+        'core_compatibility_range' => 'Requires Drupal core: 8.8.0 to 8.9.2',
       ],
       '1.2.3' => [
         'core_compatibility' => '^8.9 || ^9',
-        'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.0 to 9.0.2',
+        'core_compatible' => FALSE,
+        'core_compatibility_range' => 'Requires Drupal core: 8.9.0 to 9.0.2',
       ],
       '1.2.4' => [
         'core_compatibility' => '^8.9.2 || ^9',
-        'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.2 to 9.0.2',
+        'core_compatible' => FALSE,
+        'core_compatibility_range' => 'Requires Drupal core: 8.9.2 to 9.0.2',
       ],
       '1.2.6' => [],
     ];
     $test_cases['with 9 full releases']['expected_security_updates'] = [
       '1.2.5' => [
         'core_compatibility' => '8.9.0 || 8.9.2 || ^9.0.1',
-        'core_compatibility_message' => 'This module is compatible with Drupal core: 8.9.0, 8.9.2, 9.0.1 to 9.0.2',
+        'core_compatible' => FALSE,
+        'core_compatibility_range' => 'Requires Drupal core: 8.9.0, 8.9.2, 9.0.1 to 9.0.2',
       ],
     ];
     return $test_cases;