diff --git a/core/lib/Drupal/Core/Extension/Dependency.php b/core/lib/Drupal/Core/Extension/Dependency.php
index 572c807241..31f67d3675 100644
--- a/core/lib/Drupal/Core/Extension/Dependency.php
+++ b/core/lib/Drupal/Core/Extension/Dependency.php
@@ -8,7 +8,7 @@
 /**
  * A value object representing dependency information.
  */
-class Dependency {
+class Dependency implements DependencyInterface {
 
   /**
    * The name of the dependency.
@@ -97,8 +97,8 @@ protected function getConstraint() {
   /**
    * {@inheritdoc}
    */
-  public function isCompatible($dependee_version) {
-    return $this->getConstraint()->isCompatible($dependee_version);
+  public function isCompatible($version) {
+    return $this->getConstraint()->isCompatible($version);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Extension/Dependency/Composer.php b/core/lib/Drupal/Core/Extension/Dependency/Composer.php
index ff542d542f..8c646b4fed 100644
--- a/core/lib/Drupal/Core/Extension/Dependency/Composer.php
+++ b/core/lib/Drupal/Core/Extension/Dependency/Composer.php
@@ -28,7 +28,8 @@ class Composer implements DependencyInterface {
    *
    * @param string $constraint
    *   String constraint.
-   * @param $name
+   * @param string $name
+   *   Dependency name.
    */
   public function __construct($constraint, $name) {
     $this->constraint = $constraint;
@@ -45,8 +46,8 @@ public function getName() {
   /**
    * {@inheritdoc}
    */
-  public function isCompatible($dependee_version) {
-    return Semver::satisfies($dependee_version, $this->constraint);
+  public function isCompatible($version) {
+    return Semver::satisfies($version, $this->constraint);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Extension/Dependency/DependencyInterface.php b/core/lib/Drupal/Core/Extension/Dependency/DependencyInterface.php
index e9142e3694..c79dd1dbdf 100644
--- a/core/lib/Drupal/Core/Extension/Dependency/DependencyInterface.php
+++ b/core/lib/Drupal/Core/Extension/Dependency/DependencyInterface.php
@@ -10,16 +10,16 @@ interface DependencyInterface {
   /**
    * Determines if the provided version is compatible with this dependency.
    *
-   * @param string $dependee_version
-   *   The dependee version to check, for example '4.2'.
+   * @param string $version
+   *   The version to check, for example '4.2'.
    *
    * @return bool
    *   TRUE if compatible with the provided version, FALSE if not.
    */
-  public function isCompatible($dependee_version);
+  public function isCompatible($version);
 
   /**
-   * Gets dependency name.
+   * Gets the dependency name.
    *
    * @return string
    *   Dependency name.
@@ -27,7 +27,7 @@ public function isCompatible($dependee_version);
   public function getName();
 
   /**
-   * Gets constraint string from the dependency.
+   * Gets the constraint string from the dependency.
    *
    * @return string
    *   The constraint string.
diff --git a/core/lib/Drupal/Core/Extension/InfoParserDynamic.php b/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
index a5cd9660e1..ac34570234 100644
--- a/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
+++ b/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
@@ -26,36 +26,13 @@ class InfoParserDynamic implements InfoParserInterface {
   /**
    * The earliest Drupal version that supports 'composer.json' for dependencies.
    */
-  const FIRST_COMPOSER_JSON_SUPPORTED_VERSION = '8.9.0';
+  const FIRST_COMPOSER_JSON_SUPPORTED_VERSION = '9.1.0';
 
   /**
-   * The key for composer dependencies under extension 'info'.
+   * The key where you'll find Composer dependencies in *.info.yml files.
    */
   const COMPOSER_DEPENDENCIES = 'composer_dependencies';
 
-  /**
-   * Determines if a version satisfies the given constraints.
-   *
-   * This method uses \Composer\Semver\Semver::satisfies() but returns FALSE if
-   * the version or constraints are not valid instead of throwing an exception.
-   *
-   * @param string $version
-   *   The version.
-   * @param string $constraints
-   *   The constraints.
-   *
-   * @return bool
-   *   TRUE if the version satisfies the constraints, otherwise FALSE.
-   */
-  protected static function satisfies($version, $constraints) {
-    try {
-      return Semver::satisfies($version, $constraints);
-    }
-    catch (\UnexpectedValueException $exception) {
-      return FALSE;
-    }
-  }
-
   /**
    * InfoParserDynamic constructor.
    *
@@ -107,12 +84,12 @@ public function parse($filename) {
           $parsed_info['core_version_requirement'] = \Drupal::VERSION;
         }
         else {
+          // Non-core extensions must specify core compatibility.
           if (isset($parsed_info['dependencies'])) {
-            throw new InfoParserException("If the 'dependencies' key is used the 'core' or 'core_version_requirement' key is required in $filename");
+            throw new InfoParserException("If the 'dependencies' key is used, the 'core' or 'core_version_requirement' key is required in $filename");
           }
           if (!$has_composer_file) {
-            // Non-core extensions must specify core compatibility.
-            throw new InfoParserException("If the 'core' or 'core_version_requirement' key is not provided a composer.json file is required in $filename");
+            throw new InfoParserException("If the 'core' or 'core_version_requirement' key is not provided, a composer.json file is required in $filename");
           }
         }
         if ($has_composer_file) {
@@ -122,8 +99,10 @@ public function parse($filename) {
         if (isset($parsed_info['core']) && !preg_match("/^\d\.x$/", $parsed_info['core'])) {
           throw new InfoParserException("Invalid 'core' value \"{$parsed_info['core']}\" in " . $filename);
         }
+        // Check if the core requirement is for a version of core that can't be
+        // used with core_version_requirement.
         if (static::isConstraintSatisfiedByPreviousVersion($parsed_info['core_version_requirement'], static::FIRST_COMPOSER_JSON_SUPPORTED_VERSION)) {
-          throw new InfoParserException('Core versions before ' . static::FIRST_COMPOSER_JSON_SUPPORTED_VERSION . " must be specified in the module info.yml in $filename");
+          throw new InfoParserException('Core versions before ' . static::FIRST_COMPOSER_JSON_SUPPORTED_VERSION . " must be specified in the module info.yml file: $filename");
         }
       }
       if (isset($parsed_info['core_version_requirement'])) {
@@ -175,7 +154,7 @@ protected function getRequiredKeys() {
   }
 
   /**
-   * Determines if a constraint is satisfied by earlier versions of Drupal 8.
+   * Determines if a constraint is satisfied by earlier versions of Drupal.
    *
    * @param string $constraint
    *   A core semantic version constraint.
@@ -248,17 +227,21 @@ protected static function getAllPreviousCoreVersions($version) {
   }
 
   /**
-   * Parses a composer.json file.
+   * Parses a composer.json file and checks for core_version_requirement.
    *
-   * @param string $filename
-   *   The file name.
+   * @param string $file_path
+   *   Full path to the composer.json file.
    *
    * @return array
-   *   Parsed composer.json file.
+   *   Parsed composer.json file data.
+   *
+   * @throws \Drupal\Core\Extension\InfoParserException
+   *   Thrown when the file cannot be parsed, or when the parsed require key
+   *   does not include the drupal/core package.
    */
-  protected function parseComposerFile($filename) {
-    if (!$parsed_info = json_decode(file_get_contents($filename), TRUE)) {
-      throw new InfoParserException("Unable to parse $filename " . json_last_error_msg());
+  protected function parseComposerFile($file_path) {
+    if (!$parsed_info = json_decode(file_get_contents($file_path), TRUE)) {
+      throw new InfoParserException("Unable to parse $file_path " . json_last_error_msg());
     }
 
     $require = $parsed_info['require'];
@@ -274,7 +257,7 @@ protected function parseComposerFile($filename) {
       $parsed_info[static::COMPOSER_DEPENDENCIES][$name] = $constraint;
     }
     if (empty($parsed_info['core_version_requirement'])) {
-      throw new InfoParserException("The require key must at least specify a 'drupal/core' version in $filename");
+      throw new InfoParserException("The 'require' key must at least specify a 'drupal/core' version in $file_path");
     }
     return $parsed_info;
   }
diff --git a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
index 38114c9b35..04b44787c4 100644
--- a/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
+++ b/core/lib/Drupal/Core/Extension/ModuleExtensionList.php
@@ -209,8 +209,8 @@ protected function getInstalledExtensionNames() {
    */
   protected function ensureRequiredDependencies(Extension $module, array $modules = []) {
     if (!empty($module->info['required'])) {
-      // Modern composer.json file.
       if (!empty($module->info[InfoParserDynamic::COMPOSER_DEPENDENCIES])) {
+        // Composer-based dependencies.
         $dependencies = array_keys($module->info[InfoParserDynamic::COMPOSER_DEPENDENCIES]);
       }
       else {
diff --git a/core/modules/system/tests/modules/composer_dependencies_test/composer_dependencies_test.info.yml b/core/modules/system/tests/modules/composer_dependencies_test/composer_dependencies_test.info.yml
index 1ad12b776c..b124807860 100644
--- a/core/modules/system/tests/modules/composer_dependencies_test/composer_dependencies_test.info.yml
+++ b/core/modules/system/tests/modules/composer_dependencies_test/composer_dependencies_test.info.yml
@@ -1,5 +1,5 @@
 name: 'Module composer dependencies test'
 type: module
-description: 'Support module for test composer dependencies.'
+description: 'Support module for testing composer dependencies.'
 package: Testing
 version: VERSION
diff --git a/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php b/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
index 763308b38b..9f64b4a6d5 100644
--- a/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
@@ -103,7 +103,7 @@ public function testModulesListFormWithInvalidInfoFile() {
       $this->assertSession()->elementExists('xpath', '//input[@name="text"]');
 
       // Confirm that the error message is shown.
-      $this->assertSession()->pageTextContains("If the 'core' or 'core_version_requirement' key is not provided a composer.json file is required in " . $path . '/broken.info.yml');
+      $this->assertSession()->pageTextContains("If the 'core' or 'core_version_requirement' key is not provided, a composer.json file is required in $filename" . $path . '/broken.info.yml');
 
       // Check that the module filter text box is available.
       $this->assertSession()->elementExists('xpath', '//input[@name="text"]');
diff --git a/core/modules/system/tests/src/Functional/Module/DependencyTest.php b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
index 50e47a275f..bdbc7a3056 100644
--- a/core/modules/system/tests/src/Functional/Module/DependencyTest.php
+++ b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
@@ -77,8 +77,8 @@ public function testMissingModules() {
   public function testIncompatibleModuleVersionDependency() {
     $assert_session = $this->assertSession();
     $this->drupalGet('admin/modules');
-    // Test that the system_incompatible_module_version_dependencies_test which
-    // uses an info.yml file for dependencies is marked as having an
+    // Test that the system_incompatible_module_version_dependencies_test,
+    // which uses an info.yml file for dependencies, is marked as having an
     // incompatible dependency.
     $this->assertRaw(t('@module (<span class="admin-missing">incompatible with</span> version @version)', [
       '@module' => 'System incompatible module version test (>2.0)',
@@ -87,8 +87,8 @@ public function testIncompatibleModuleVersionDependency() {
     $checkbox = $this->xpath('//input[@type="checkbox" and @disabled="disabled" and @name="modules[system_incompatible_module_version_dependencies_test][enable]"]');
     $this->assertCount(1, $checkbox, 'Checkbox for the module is disabled.');
     $assert_session->fieldDisabled('modules[system_incompatible_module_version_dependencies_test][enable]');
-    // Test that the composer_incompatible_module_version_dependencies_test
-    // which uses a composer.yml file for dependencies is marked as having an
+    // Test that the composer_incompatible_module_version_dependencies_test,
+    // which uses a composer.json file for dependencies, is marked as having an
     // incompatible dependency.
     $assert_session->responseContains('System incompatible module version test (^2) (<span class="admin-missing">incompatible with</span> version 1.0)');
     $assert_session->fieldDisabled('modules[composer_incompatible_module_version_dependencies_test][enable]');
@@ -106,24 +106,24 @@ public function testIncompatibleCoreVersionDependency() {
     ]), 'A module that depends on a module with an incompatible core version is marked as such.');
     $checkbox = $this->xpath('//input[@type="checkbox" and @disabled="disabled" and @name="modules[system_incompatible_core_version_dependencies_test][enable]"]');
     $this->assertCount(1, $checkbox, 'Checkbox for the module is disabled.');
-    // Test that module using an info.yml file with a dependency that is using a
-    // info.yml with a incompatible core version is marked as having an
-    // incompatible dependency.
+    // Test that a module using an info.yml file, with a dependency that is
+    // also using an info.yml file, that requires an incompatible version of
+    // core, is marked as having an incompatible dependency.
     $assert_session->elementContains('css', '#edit-modules-system-incompatible-core-version-dependencies-test-enable-description', 'System incompatible core version test (<span class="admin-missing">incompatible with</span> this version of Drupal core)');
     $assert_session->fieldDisabled('modules[system_incompatible_core_version_dependencies_test][enable]');
-    // Test that module using an composer.json file with a dependency that is
-    // using a info.yml with a incompatible core version is marked as having an
-    // incompatible dependency.
+    // Test that a module using a composer.json file. with a dependency that is
+    // using an info.yml with an incompatible core version, is marked as having
+    // an incompatible dependency.
     $assert_session->elementContains('css', '#edit-modules-composer-incompatible-core-depend-test-enable-description', 'System incompatible core version test (<span class="admin-missing">incompatible with</span> this version of Drupal core)');
     $assert_session->fieldDisabled('modules[composer_incompatible_core_depend_test][enable]');
-    // Test that module using an info.yml file with a dependency that is using a
-    // composer.json with a incompatible core version is marked as having an
-    // incompatible dependency.
+    // Test that a module using an info.yml file with a dependency that is
+    // using a composer.json with an incompatible core version is marked as
+    // having an incompatible dependency.
     $assert_session->elementContains('css', '#edit-modules-system-incompatible-core-composer-depend-test-enable-description', 'System core incompatible composer.json test (<span class="admin-missing">incompatible with</span> this version of Drupal core)');
     $assert_session->fieldDisabled('modules[composer_incompatible_core_composer_depend_test][enable]');
-    // Test that module using an composer.json file with a dependency that is
-    // using a composer.json with a incompatible core version is marked as
-    // having an incompatible dependency.
+    // Test that a module using a composer.json file with a dependency that is
+    // using a composer.json file with an incompatible core version is marked
+    // as having an incompatible dependency.
     $assert_session->elementContains('css', '#edit-modules-composer-incompatible-core-composer-depend-test-enable-description', 'System core incompatible composer.json test (<span class="admin-missing">incompatible with</span> this version of Drupal core)');
     $assert_session->fieldDisabled('modules[composer_incompatible_core_composer_depend_test][enable]');
   }
diff --git a/core/tests/Drupal/KernelTests/Core/Extension/ModuleInstallerTest.php b/core/tests/Drupal/KernelTests/Core/Extension/ModuleInstallerTest.php
index 1fb0a69fae..804527d319 100644
--- a/core/tests/Drupal/KernelTests/Core/Extension/ModuleInstallerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Extension/ModuleInstallerTest.php
@@ -130,8 +130,6 @@ public function providerTestInvalidCoreInstall() {
    */
   public function testDependencyInvalidCoreInstall($module, $dependency) {
     $this->expectException(MissingDependencyException::class);
-    $this->expectExceptionMessage("Unable to install modules: module 'system_incompatible_core_version_dependencies_test'. Its dependency module 'system_core_incompatible_semver_test' is incompatible with this version of Drupal core.");
-    $this->container->get('module_installer')->install(['system_incompatible_core_version_dependencies_test']);
     $this->expectExceptionMessage("Unable to install modules: module '$module'. Its dependency module '$dependency' is incompatible with this version of Drupal core.");
     $this->container->get('module_installer')->install([$module]);
   }
@@ -141,11 +139,11 @@ public function testDependencyInvalidCoreInstall($module, $dependency) {
    */
   public function providerDependencyInvalidCoreInstall() {
     return [
-      'info with info dependency' => [
+      'info with info.yml dependency' => [
         'system_incompatible_core_version_dependencies_test',
         'system_incompatible_core_version_test',
       ],
-      'composer.json with info dependency' => [
+      'composer.json with info.yml dependency' => [
         'composer_incompatible_core_depend_test',
         'system_incompatible_core_version_test',
       ],
@@ -161,7 +159,7 @@ public function providerDependencyInvalidCoreInstall() {
   }
 
   /**
-   * Tests no dependencies install with a dependency with invalid core.
+   * Tests invalid core install, without installing dependencies.
    *
    * @dataProvider provideDependencyInvalidCoreInstallNoDependencies
    * @covers ::install
@@ -175,10 +173,10 @@ public function testDependencyInvalidCoreInstallNoDependencies($module) {
    */
   public function provideDependencyInvalidCoreInstallNoDependencies() {
     return [
-      'info with info dependency' => [
+      'info with info.yml dependency' => [
         'system_incompatible_core_version_dependencies_test',
       ],
-      'composer.json with info dependency' => [
+      'composer.json with info.yml dependency' => [
         'composer_incompatible_core_depend_test',
       ],
       'composer.json with composer.json dependency' => [
diff --git a/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php b/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
index 69f7a52064..62efc21d18 100644
--- a/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
@@ -137,7 +137,7 @@ public function testMissingCoreCoreVersionRequirement() {
         'missing_core_and_core_version_requirement-duplicate.info.txt' => $missing_core_and_core_version_requirement,
       ],
     ]);
-    $exception_message = "If the 'core' or 'core_version_requirement' key is not provided a composer.json file is required in vfs://modules/fixtures/missing_core_and_core_version_requirement";
+    $exception_message = "If the 'core' or 'core_version_requirement' key is not provided, a composer.json file is required in vfs://modules/fixtures/missing_core_and_core_version_requirement";
     // Set the expected exception for the 2nd call to parse().
     $this->expectException('\Drupal\Core\Extension\InfoParserException');
     $this->expectExceptionMessage("$exception_message-duplicate.info.txt");
@@ -730,9 +730,9 @@ public function testComposerJson() {
 "type": "drupal-module",
 "license": "GPL-2.0-or-later",
 "require": {
-"drupal/core": "^8.8",
-"drupal/field": "~8.0",
-"smurfcore/log": "~1.0"
+  "drupal/core": "^8.8",
+  "drupal/field": "~8.0",
+  "smurfcore/log": "~1.0"
 },
 "version": "VERSION"
 }