diff --git a/test/tasks/Request4SuspendKtTest.kt b/test/tasks/Request4SuspendKtTest.kt
index af92edb..a343a5c 100644
--- a/test/tasks/Request4SuspendKtTest.kt
+++ b/test/tasks/Request4SuspendKtTest.kt
@@ -3,29 +3,23 @@ package tasks
 import contributors.MockGithubService
 import contributors.expectedResults
 import contributors.testRequestData
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runBlockingTest
 import org.junit.Assert
 import org.junit.Test
 
+@UseExperimental(ExperimentalCoroutinesApi::class)
 class Request4SuspendKtTest {
     @Test
-    fun testSuspend() = runBlocking {
-        val startTime = System.currentTimeMillis()
+    fun testSuspend() = runBlockingTest {
+        val startTime = currentTime
         val result = loadContributorsSuspend(MockGithubService, testRequestData)
         Assert.assertEquals("Wrong result for 'loadContributorsSuspend'", expectedResults.users, result)
-        val totalTime = System.currentTimeMillis() - startTime
-        /*
-        // TODO: uncomment this assertion
+        val totalTime = currentTime - startTime
         Assert.assertEquals(
-            "The calls run consequently, so the total virtual time should be 4000 ms: " +
-                    "1000 for repos request plus (1000 + 1200 + 800) = 3000 for sequential contributors requests)",
+            "The calls run consequently," +
+                    "so the total virtual time should be 4000 ms: ",
             expectedResults.timeFromStart, totalTime
         )
-        */
-        Assert.assertTrue(
-            "The calls run consequently, so the total time should be around 4000 ms: " +
-                    "1000 for repos request plus (1000 + 1200 + 800) = 3000 for sequential contributors requests)",
-            totalTime in expectedResults.timeFromStart..(expectedResults.timeFromStart + 500)
-        )
     }
 }
\ No newline at end of file
diff --git a/test/tasks/Request5ConcurrentKtTest.kt b/test/tasks/Request5ConcurrentKtTest.kt
index 24c7e94..82d0846 100644
--- a/test/tasks/Request5ConcurrentKtTest.kt
+++ b/test/tasks/Request5ConcurrentKtTest.kt
@@ -3,29 +3,23 @@ package tasks
 import contributors.MockGithubService
 import contributors.expectedConcurrentResults
 import contributors.testRequestData
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runBlockingTest
 import org.junit.Assert
 import org.junit.Test
 
+@UseExperimental(ExperimentalCoroutinesApi::class)
 class Request5ConcurrentKtTest {
     @Test
-    fun testConcurrent() = runBlocking {
-        val startTime = System.currentTimeMillis()
+    fun testConcurrent() = runBlockingTest {
+        val startTime = currentTime
         val result = loadContributorsConcurrent(MockGithubService, testRequestData)
         Assert.assertEquals("Wrong result for 'loadContributorsConcurrent'", expectedConcurrentResults.users, result)
-        val totalTime = System.currentTimeMillis() - startTime
-        /*
-        // TODO: uncomment this assertion
+        val totalTime = currentTime - startTime
         Assert.assertEquals(
             "The calls run concurrently, so the total virtual time should be 2200 ms: " +
                     "1000 ms for repos request plus max(1000, 1200, 800) = 1200 ms for concurrent contributors requests)",
             expectedConcurrentResults.timeFromStart, totalTime
         )
-        */
-        Assert.assertTrue(
-            "The calls run concurrently, so the total virtual time should be 2200 ms: " +
-                    "1000 ms for repos request plus max(1000, 1200, 800) = 1200 ms for concurrent contributors requests)",
-            totalTime in expectedConcurrentResults.timeFromStart..(expectedConcurrentResults.timeFromStart + 500)
-        )
     }
 }
\ No newline at end of file
diff --git a/test/tasks/Request6ProgressKtTest.kt b/test/tasks/Request6ProgressKtTest.kt
index 4c9e441..a8da26d 100644
--- a/test/tasks/Request6ProgressKtTest.kt
+++ b/test/tasks/Request6ProgressKtTest.kt
@@ -3,24 +3,23 @@ package tasks
 import contributors.MockGithubService
 import contributors.progressResults
 import contributors.testRequestData
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runBlockingTest
 import org.junit.Assert
 import org.junit.Test
 
+@UseExperimental(ExperimentalCoroutinesApi::class)
 class Request6ProgressKtTest {
     @Test
-    fun testProgress() = runBlocking {
-        val startTime = System.currentTimeMillis()
+    fun testProgress() = runBlockingTest {
+        val startTime = currentTime
         var index = 0
         loadContributorsProgress(MockGithubService, testRequestData) {
             users, _ ->
             val expected = progressResults[index++]
-            val time = System.currentTimeMillis() - startTime
-            /*
-            // TODO: uncomment this assertion
+            val time = currentTime - startTime
             Assert.assertEquals("Expected intermediate result after virtual ${expected.timeFromStart} ms:",
                 expected.timeFromStart, time)
-            */
             Assert.assertEquals("Wrong intermediate result after $time:", expected.users, users)
         }
     }
diff --git a/test/tasks/Request7ChannelsKtTest.kt b/test/tasks/Request7ChannelsKtTest.kt
index d82d26a..628dc8e 100644
--- a/test/tasks/Request7ChannelsKtTest.kt
+++ b/test/tasks/Request7ChannelsKtTest.kt
@@ -3,24 +3,23 @@ package tasks
 import contributors.MockGithubService
 import contributors.concurrentProgressResults
 import contributors.testRequestData
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runBlockingTest
 import org.junit.Assert
 import org.junit.Test
 
+@UseExperimental(ExperimentalCoroutinesApi::class)
 class Request7ChannelsKtTest {
     @Test
-    fun testChannels() = runBlocking {
-        val startTime = System.currentTimeMillis()
+    fun testChannels() = runBlockingTest {
+        val startTime = currentTime
         var index = 0
         loadContributorsChannels(MockGithubService, testRequestData) {
                 users, _ ->
             val expected = concurrentProgressResults[index++]
-            val time = System.currentTimeMillis() - startTime
-            /*
-            // TODO: uncomment this assertion
+            val time = currentTime - startTime
             Assert.assertEquals("Expected intermediate result after virtual ${expected.timeFromStart} ms:",
-                expected.timeFromStart, virtualTime)
-            */
+                expected.timeFromStart, time)
             Assert.assertEquals("Wrong intermediate result after $time:", expected.users, users)
         }
     }