diff --git a/rxpm/src/main/kotlin/me/dmdev/rxpm/PresentationModel.kt b/rxpm/src/main/kotlin/me/dmdev/rxpm/PresentationModel.kt
index aac0e44..495820b 100644
--- a/rxpm/src/main/kotlin/me/dmdev/rxpm/PresentationModel.kt
+++ b/rxpm/src/main/kotlin/me/dmdev/rxpm/PresentationModel.kt
@@ -26,7 +26,7 @@ abstract class PresentationModel {
     /**
      * The [lifecycle][Lifecycle] of this presentation model.
      */
-    val lifecycleObservable = lifecycle.distinctUntilChanged()
+    val lifecycleObservable: Observable<Lifecycle> = lifecycle.distinctUntilChanged()
     internal val lifecycleConsumer = lifecycle.asConsumer()
 
     /**
@@ -116,13 +116,9 @@ abstract class PresentationModel {
      */
     fun attachToParent(parent: PresentationModel) {
 
-        if (parent == this) {
-            throw IllegalArgumentException("Presentation model can't be attached to itself.")
-        }
+        require(parent != this) { "Presentation model can't be attached to itself." }
 
-        if (lifecycle.hasValue()) {
-            throw IllegalStateException("Presentation model can't be a child more than once. It must not be reused.")
-        }
+        check(!lifecycle.hasValue()) { "Presentation model can't be a child more than once. It must not be reused." }
 
         when (parent.lifecycle.value) {
 
diff --git a/rxpm/src/main/kotlin/me/dmdev/rxpm/State.kt b/rxpm/src/main/kotlin/me/dmdev/rxpm/State.kt
index 4e4b1a0..ed170c4 100644
--- a/rxpm/src/main/kotlin/me/dmdev/rxpm/State.kt
+++ b/rxpm/src/main/kotlin/me/dmdev/rxpm/State.kt
@@ -132,7 +132,7 @@ infix fun <T> State<T>.bindTo(consumer: (T) -> Unit) {
 interface DiffStrategy<T> {
 
     /**
-     * Сompares the old and the new values.
+     * Compares the old and the new values.
      * @return [true] if both values ​​are identical or [false] if they are different.
      */
     fun areTheSame(new: T, old: T): Boolean
diff --git a/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmActivityDelegate.kt b/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmActivityDelegate.kt
index 399548a..3b950d2 100644
--- a/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmActivityDelegate.kt
+++ b/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmActivityDelegate.kt
@@ -91,13 +91,13 @@ class PmActivityDelegate<PM, A>(
         commonDelegate.onUnbind()
 
         when (retainMode) {
-            RetainMode.IS_FINISHING -> {
+            IS_FINISHING -> {
                 if (pmActivity.isFinishing) {
                     commonDelegate.onDestroy()
                 }
             }
 
-            RetainMode.CONFIGURATION_CHANGES -> {
+            CONFIGURATION_CHANGES -> {
                 if (!pmActivity.isChangingConfigurations) {
                     commonDelegate.onDestroy()
                 }
diff --git a/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmFragmentDelegate.kt b/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmFragmentDelegate.kt
index 10fe3ed..b0c681a 100644
--- a/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmFragmentDelegate.kt
+++ b/rxpm/src/main/kotlin/me/dmdev/rxpm/delegate/PmFragmentDelegate.kt
@@ -96,7 +96,7 @@ class PmFragmentDelegate<PM, F>(
      */
     fun onDestroy() {
         when (retainMode) {
-            RetainMode.SAVED_STATE -> {
+            SAVED_STATE -> {
                 if (pmFragment.activity?.isFinishing == true
                     || (pmFragment.fragmentManager?.isStateSaved?.not() == true)
                 ) {
@@ -104,7 +104,7 @@ class PmFragmentDelegate<PM, F>(
                 }
             }
 
-            RetainMode.CONFIGURATION_CHANGES -> {
+            CONFIGURATION_CHANGES -> {
                 if (pmFragment.activity?.isChangingConfigurations?.not() == true) {
                     commonDelegate.onDestroy()
                 }
diff --git a/rxpm/src/main/kotlin/me/dmdev/rxpm/test/PmTestHelper.kt b/rxpm/src/main/kotlin/me/dmdev/rxpm/test/PmTestHelper.kt
index 9ce676d..98c8e62 100644
--- a/rxpm/src/main/kotlin/me/dmdev/rxpm/test/PmTestHelper.kt
+++ b/rxpm/src/main/kotlin/me/dmdev/rxpm/test/PmTestHelper.kt
@@ -12,8 +12,6 @@ class PmTestHelper(val pm: PresentationModel) {
 
     enum class LifecycleSteps { ALL, BYPASS_BINDING, BYPASS_RESUMING }
 
-    private val lifecycleStates = PresentationModel.Lifecycle.values()
-
     /**
      * Sets the lifecycle of the [presentation model][pm] under test to the specified [state][lifecycleState].
      * This will also create natural sequence of states before the requested one.
@@ -79,14 +77,10 @@ class PmTestHelper(val pm: PresentationModel) {
 
     private fun checkStateAllowed(lifecycleState: PresentationModel.Lifecycle) {
         pm.currentLifecycleState?.let { currentState ->
-            if (lifecycleState <= currentState
-                && !isBindedAgain(lifecycleState)
-                && !isResumedAgain((lifecycleState))
-            ) {
-                throw IllegalStateException(
-                    "You can't set lifecycle state as $lifecycleState when it already is $pm.currentLifecycleState."
-                )
-            }
+            check(!(lifecycleState <= currentState
+            && !isBindedAgain(lifecycleState)
+            && !isResumedAgain((lifecycleState)))
+            ) { "You can't set lifecycle state as $lifecycleState when it already is $pm.currentLifecycleState." }
         }
     }
 
diff --git a/rxpm/src/test/kotlin/me/dmdev/rxpm/util/SchedulersRule.kt b/rxpm/src/test/kotlin/me/dmdev/rxpm/util/SchedulersRule.kt
index d1baacc..b3e66b9 100644
--- a/rxpm/src/test/kotlin/me/dmdev/rxpm/util/SchedulersRule.kt
+++ b/rxpm/src/test/kotlin/me/dmdev/rxpm/util/SchedulersRule.kt
@@ -1,10 +1,9 @@
 package me.dmdev.rxpm.util
 
-import io.reactivex.android.plugins.RxAndroidPlugins
-import io.reactivex.plugins.RxJavaPlugins
-import io.reactivex.schedulers.Schedulers
-import io.reactivex.schedulers.TestScheduler
-import org.junit.rules.ExternalResource
+import io.reactivex.android.plugins.*
+import io.reactivex.plugins.*
+import io.reactivex.schedulers.*
+import org.junit.rules.*
 
 class SchedulersRule(private val useTestScheduler: Boolean = false) : ExternalResource() {
 
@@ -12,7 +11,7 @@ class SchedulersRule(private val useTestScheduler: Boolean = false) : ExternalRe
 
     val testScheduler: TestScheduler
         get() {
-            if (!useTestScheduler) throw IllegalStateException("TestScheduler is switched off.")
+            check(useTestScheduler) { "TestScheduler is switched off." }
             return _testScheduler
         }