diff --git a/src/test/kotlin/g1101_1200/s1110_delete_nodes_and_return_forest/SolutionTest.kt b/src/test/kotlin/g1101_1200/s1110_delete_nodes_and_return_forest/SolutionTest.kt
index 6104062c8..37ca600db 100644
--- a/src/test/kotlin/g1101_1200/s1110_delete_nodes_and_return_forest/SolutionTest.kt
+++ b/src/test/kotlin/g1101_1200/s1110_delete_nodes_and_return_forest/SolutionTest.kt
@@ -4,16 +4,15 @@ import com_github_leetcode.TreeNode
 import org.hamcrest.CoreMatchers.equalTo
 import org.hamcrest.MatcherAssert.assertThat
 import org.junit.jupiter.api.Test
-import java.util.Arrays
 
 internal class SolutionTest {
     @Test
     fun delNodes() {
-        val root = TreeNode.create(mutableListOf<Int?>(1, 2, 3, 4, 5, 6, 7))
+        val root = TreeNode.create(mutableListOf(1, 2, 3, 4, 5, 6, 7))
         assertThat(
             Solution().delNodes(root, intArrayOf(3, 5)).toString(),
             equalTo(
-                Arrays.asList<Any?>(
+                listOf(
                     TreeNode.create(mutableListOf(1, 2, null, 4)),
                     TreeNode.create(listOf(6)),
                     TreeNode.create(listOf(7)),
@@ -29,7 +28,7 @@ internal class SolutionTest {
         assertThat(
             Solution().delNodes(root, intArrayOf(3)).toString(),
             equalTo(
-                listOf<Any?>(TreeNode.create(mutableListOf<Int?>(1, 2, 4))).toString(),
+                listOf(TreeNode.create(mutableListOf(1, 2, 4))).toString(),
             ),
         )
     }
diff --git a/src/test/kotlin/g1101_1200/s1123_lowest_common_ancestor_of_deepest_leaves/SolutionTest.kt b/src/test/kotlin/g1101_1200/s1123_lowest_common_ancestor_of_deepest_leaves/SolutionTest.kt
index c60a49331..76d74950d 100644
--- a/src/test/kotlin/g1101_1200/s1123_lowest_common_ancestor_of_deepest_leaves/SolutionTest.kt
+++ b/src/test/kotlin/g1101_1200/s1123_lowest_common_ancestor_of_deepest_leaves/SolutionTest.kt
@@ -21,7 +21,7 @@ internal class SolutionTest {
     @Test
     fun lcaDeepestLeaves2() {
         assertThat(
-            Solution().lcaDeepestLeaves(TreeNode.create(mutableListOf<Int?>(1))).toString(),
+            Solution().lcaDeepestLeaves(TreeNode.create(mutableListOf(1))).toString(),
             equalTo("1"),
         )
     }
diff --git a/src/test/kotlin/g3301_3400/s3387_maximize_amount_after_two_days_of_conversions/SolutionTest.kt b/src/test/kotlin/g3301_3400/s3387_maximize_amount_after_two_days_of_conversions/SolutionTest.kt
index 9359570f9..f96f62e99 100644
--- a/src/test/kotlin/g3301_3400/s3387_maximize_amount_after_two_days_of_conversions/SolutionTest.kt
+++ b/src/test/kotlin/g3301_3400/s3387_maximize_amount_after_two_days_of_conversions/SolutionTest.kt
@@ -7,7 +7,7 @@ import org.junit.jupiter.api.Test
 internal class SolutionTest {
     @Test
     fun maxAmount() {
-        assertThat<Double?>(
+        assertThat<Double>(
             Solution()
                 .maxAmount(
                     "EUR",
diff --git a/src/test/kotlin/g3301_3400/s3388_count_beautiful_splits_in_an_array/SolutionTest.kt b/src/test/kotlin/g3301_3400/s3388_count_beautiful_splits_in_an_array/SolutionTest.kt
index 1701232b7..878327d9a 100644
--- a/src/test/kotlin/g3301_3400/s3388_count_beautiful_splits_in_an_array/SolutionTest.kt
+++ b/src/test/kotlin/g3301_3400/s3388_count_beautiful_splits_in_an_array/SolutionTest.kt
@@ -15,9 +15,9 @@ internal class SolutionTest {
 
     @Test
     fun beautifulSplits2() {
-        assertThat<Int?>(
+        assertThat<Int>(
             Solution().beautifulSplits(intArrayOf(1, 2, 3, 4)),
-            equalTo<Int?>(0),
+            equalTo<Int>(0),
         )
     }
 }
diff --git a/src/test/kotlin/g3301_3400/s3389_minimum_operations_to_make_character_frequencies_equal/SolutionTest.kt b/src/test/kotlin/g3301_3400/s3389_minimum_operations_to_make_character_frequencies_equal/SolutionTest.kt
index 4f842947b..b0a83bb9e 100644
--- a/src/test/kotlin/g3301_3400/s3389_minimum_operations_to_make_character_frequencies_equal/SolutionTest.kt
+++ b/src/test/kotlin/g3301_3400/s3389_minimum_operations_to_make_character_frequencies_equal/SolutionTest.kt
@@ -12,7 +12,7 @@ internal class SolutionTest {
 
     @Test
     fun makeStringGood2() {
-        assertThat<Int?>(Solution().makeStringGood("wddw"), equalTo<Int>(0))
+        assertThat<Int>(Solution().makeStringGood("wddw"), equalTo<Int>(0))
     }
 
     @Test