diff --git a/src/test/kotlin/g0301_0400/s0399_evaluate_division/SolutionTest.kt b/src/test/kotlin/g0301_0400/s0399_evaluate_division/SolutionTest.kt
index 72e2ea286..3e3fb4c74 100644
--- a/src/test/kotlin/g0301_0400/s0399_evaluate_division/SolutionTest.kt
+++ b/src/test/kotlin/g0301_0400/s0399_evaluate_division/SolutionTest.kt
@@ -8,9 +8,9 @@ import org.junit.jupiter.api.Test
 internal class SolutionTest {
     @Test
     fun calcEquation() {
-        val equations: List<List<String?>> = ArrayUtils.getLists(arrayOf(arrayOf("a", "b"), arrayOf("b", "c")))
+        val equations: List<List<String>> = ArrayUtils.getLists(arrayOf(arrayOf("a", "b"), arrayOf("b", "c")))
         val values = doubleArrayOf(2.0, 3.0)
-        val queries: List<List<String?>> = ArrayUtils.getLists(
+        val queries: List<List<String>> = ArrayUtils.getLists(
             arrayOf(
                 arrayOf("a", "c"),
                 arrayOf("b", "a"),
@@ -25,10 +25,10 @@ internal class SolutionTest {
 
     @Test
     fun calcEquation2() {
-        val equations: List<List<String?>> =
+        val equations: List<List<String>> =
             ArrayUtils.getLists(arrayOf(arrayOf("a", "b"), arrayOf("b", "c"), arrayOf("bc", "cd")))
         val values = doubleArrayOf(1.5, 2.5, 5.0)
-        val queries: List<List<String?>> =
+        val queries: List<List<String>> =
             ArrayUtils.getLists(arrayOf(arrayOf("a", "c"), arrayOf("c", "b"), arrayOf("bc", "cd"), arrayOf("cd", "bc")))
         val expected = doubleArrayOf(3.75000, 0.40000, 5.00000, 0.20000)
         assertThat(Solution().calcEquation(equations, values, queries), equalTo(expected))
@@ -36,9 +36,9 @@ internal class SolutionTest {
 
     @Test
     fun calcEquation3() {
-        val equations: List<List<String?>> = ArrayList(listOf(listOf("a", "b")))
+        val equations: List<List<String>> = ArrayList(listOf(listOf("a", "b")))
         val values = doubleArrayOf(0.5)
-        val queries: List<List<String?>> =
+        val queries: List<List<String>> =
             ArrayUtils.getLists(arrayOf(arrayOf("a", "b"), arrayOf("b", "a"), arrayOf("a", "c"), arrayOf("x", "y")))
         val expected = doubleArrayOf(0.50000, 2.00000, -1.00000, -1.00000)
         assertThat(Solution().calcEquation(equations, values, queries), equalTo(expected))
diff --git a/src/test/kotlin/g3501_3600/s3508_implement_router/RouterTest.kt b/src/test/kotlin/g3501_3600/s3508_implement_router/RouterTest.kt
index d079eacd5..424536ce6 100644
--- a/src/test/kotlin/g3501_3600/s3508_implement_router/RouterTest.kt
+++ b/src/test/kotlin/g3501_3600/s3508_implement_router/RouterTest.kt
@@ -28,7 +28,7 @@ internal class RouterTest {
         // Packet is added. Return True.
         assertThat<Boolean>(router.addPacket(5, 2, 110), equalTo<Boolean>(true))
         // The only packet with destination 5 and timestamp in the inclusive range
-        assertThat<Int?>(router.getCount(5, 100, 110), equalTo<Int?>(1))
+        assertThat<Int>(router.getCount(5, 100, 110), equalTo<Int>(1))
     }
 
     @Test