diff --git a/grails-core/src/main/groovy/grails/boot/config/GrailsApplicationPostProcessor.groovy b/grails-core/src/main/groovy/grails/boot/config/GrailsApplicationPostProcessor.groovy
index 9de746d7e8f..5c5b0d02709 100644
--- a/grails-core/src/main/groovy/grails/boot/config/GrailsApplicationPostProcessor.groovy
+++ b/grails-core/src/main/groovy/grails/boot/config/GrailsApplicationPostProcessor.groovy
@@ -68,15 +68,10 @@ class GrailsApplicationPostProcessor implements BeanDefinitionRegistryPostProces
 
     GrailsApplicationPostProcessor(GrailsApplicationLifeCycle lifeCycle, ApplicationContext applicationContext, Class...classes) {
         this.lifeCycle = lifeCycle
-        if(lifeCycle instanceof GrailsApplicationClass) {
-            this.applicationClass = (GrailsApplicationClass)lifeCycle
-        }
-        else {
-            this.applicationClass = null
-        }
-        this.classes = classes != null ? classes : [] as Class[]
-        grailsApplication = applicationClass != null ? new DefaultGrailsApplication(applicationClass) : new DefaultGrailsApplication()
-        pluginManager = new DefaultGrailsPluginManager(grailsApplication)
+        this.applicationClass = lifeCycle instanceof GrailsApplicationClass ? (GrailsApplicationClass) lifeCycle : null
+        this.classes = classes ?: [] as Class[]
+        this.grailsApplication = applicationClass ? new DefaultGrailsApplication(applicationClass) : new DefaultGrailsApplication()
+        this.pluginManager = applicationContext?.getBeanNamesForType(GrailsPluginManager) ? applicationContext.getBean(GrailsPluginManager) : new DefaultGrailsPluginManager(grailsApplication)
         if(applicationContext != null) {
             setApplicationContext(applicationContext)
         }
@@ -290,30 +285,22 @@ class GrailsApplicationPostProcessor implements BeanDefinitionRegistryPostProces
         }
     }
 
-    @SuppressWarnings("GrMethodMayBeStatic")
     private void loadPluginConfigurationsToMicronautContext(ConfigurableApplicationContext applicationContext) {
-        String[] beanNames = applicationContext.getBeanNamesForType(GrailsPluginManager)
-        if (beanNames.length == 0) {
-            // do not continue if PluginManager is not available
+        ConfigurableApplicationContext parentApplicationContext = (ConfigurableApplicationContext) applicationContext.parent
+        if (!parentApplicationContext) {
+            // No Micronaut parent context, return early
             return
         }
-
-        GrailsPluginManager pluginManager = applicationContext.getBean(GrailsPluginManager)
-        ConfigurableApplicationContext parentApplicationContext = (ConfigurableApplicationContext) applicationContext.parent
         ConfigurableEnvironment parentContextEnv = parentApplicationContext.getEnvironment()
         if (parentContextEnv instanceof MicronautEnvironment) {
-            if (log.isDebugEnabled()) {
-                log.debug("Loading configurations from the plugins to the parent Micronaut context")
-            }
+            log.debug('Loading configurations from the plugins to the parent Micronaut context')
             final io.micronaut.context.env.Environment micronautEnv = ((io.micronaut.context.env.Environment) parentContextEnv.getEnvironment())
             final GrailsPlugin[] plugins = pluginManager.allPlugins
             Integer priority = AbstractPropertySourceLoader.DEFAULT_POSITION
             Arrays.stream(plugins)
                     .filter({ GrailsPlugin plugin -> plugin.propertySource != null })
                     .forEach({ GrailsPlugin plugin ->
-                        if (log.isDebugEnabled()) {
-                            log.debug("Loading configurations from {} plugin to the parent Micronaut context", plugin.name)
-                        }
+                        log.debug('Loading configurations from {} plugin to the parent Micronaut context', plugin.name)
                         micronautEnv.addPropertySource(PropertySource.of("grails.plugins.$plugin.name", (Map) plugin.propertySource.source, --priority))
                     })
             micronautEnv.refresh()
diff --git a/grails-core/src/test/groovy/org/grails/plugins/GrailsPluginConfigurationClass.groovy b/grails-core/src/test/groovy/org/grails/plugins/GrailsPluginConfigurationClass.groovy
index 6f413170fce..65e0056a8f9 100644
--- a/grails-core/src/test/groovy/org/grails/plugins/GrailsPluginConfigurationClass.groovy
+++ b/grails-core/src/test/groovy/org/grails/plugins/GrailsPluginConfigurationClass.groovy
@@ -1,13 +1,10 @@
 package org.grails.plugins
 
 import grails.boot.config.GrailsAutoConfiguration
-import grails.core.DefaultGrailsApplication
 import grails.core.GrailsApplication
 import grails.plugins.GrailsPlugin
 import grails.plugins.GrailsPluginManager
 import groovy.transform.CompileStatic
-import org.grails.plugins.DefaultGrailsPlugin
-import org.grails.plugins.MockGrailsPluginManager
 import org.springframework.context.annotation.Bean
 import org.springframework.context.annotation.Configuration
 import org.springframework.core.io.FileSystemResource
@@ -24,17 +21,17 @@ class GrailsPluginConfigurationClass extends GrailsAutoConfiguration {
 
     @Bean(name = "grailsPluginManager")
     GrailsPluginManager getGrailsPluginManager() {
-        String tempDir = System.getProperty("java.io.tmpdir")
-        GrailsApplication grailsApplication = new DefaultGrailsApplication()
-        final MockGrailsPluginManager pluginManager = new MockGrailsPluginManager(grailsApplication)
-        final List<DefaultGrailsPlugin> plugins = createGrailsPlugins(grailsApplication)
-        plugins.forEach({ plugin -> pluginManager.registerMockPlugin((GrailsPlugin) plugin)})
-        return pluginManager
+        MockGrailsPluginManager pluginManager = new MockGrailsPluginManager()
+        createGrailsPlugins(pluginManager.application).each {
+            pluginManager.registerMockPlugin(it)
+        }
+        pluginManager
     }
 
-    private List<DefaultGrailsPlugin> createGrailsPlugins(DefaultGrailsApplication grailsApplication) {
+    private List<GrailsPlugin> createGrailsPlugins(GrailsApplication grailsApplication) {
         final String grailsVersion = '4.0.1'
         def gcl = new GroovyClassLoader()
+
         GrailsPlugin plugin = new MockTestGrailsPlugin(gcl.parseClass("""class TestGrailsPlugin {
         def version = '1.0.0'
         def grailsVersion = '$grailsVersion'
@@ -45,7 +42,8 @@ class GrailsPluginConfigurationClass extends GrailsAutoConfiguration {
         def version = '1.0.0'
         def grailsVersion = '$grailsVersion'
 }"""), grailsApplication)
-        [plugin, plugin2]
+
+        List<GrailsPlugin>.of(plugin, plugin2)
     }
 
     class MockTestGrailsPlugin extends DefaultGrailsPlugin {
@@ -82,10 +80,6 @@ class GrailsPluginConfigurationClass extends GrailsAutoConfiguration {
 
     class MockTestTwoGrailsPlugin extends DefaultGrailsPlugin {
 
-        MockTestTwoGrailsPlugin(Class<?> pluginClass, Resource resource, GrailsApplication application) {
-            super(pluginClass, resource, application)
-        }
-
         MockTestTwoGrailsPlugin(Class<?> pluginClass, GrailsApplication application) {
             super(pluginClass, application)
         }