Migrate to JUnit5 notation

from https://github.com/ProjectMapK/jackson-module-kogera/blob/ecc766d97dc4c2bec574fba7cc6bdeacc2b07c29/src/test/kotlin/io/github/projectmapk/jackson/module/kogera/zPorted/test/github/Github490.kt

Author: k163377

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/github/Github490.kt

@@ -4,8 +4,8 @@ import com.fasterxml.jackson.databind.JsonNode
 import com.fasterxml.jackson.databind.node.NullNode
 import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import com.fasterxml.jackson.module.kotlin.readValue
-import org.hamcrest.CoreMatchers
-import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNull
 import org.junit.jupiter.api.Test
 
 class TestGithub490 {
@@ -18,55 +18,45 @@ class TestGithub490 {
 
     @Test
     fun testKotlinDeserialization_intValue() {
-        assertThat(
-            "Nullable missing Int value should be deserialized as null",
-            value.intValue,
-            CoreMatchers.nullValue()
-        )
+        assertNull(value.intValue, "Nullable missing Int value should be deserialized as null")
     }
 
     @Test
     fun testKotlinDeserialization_stringValue() {
-        assertThat(
-            "Nullable missing String value should be deserialized as null",
-            value.stringValue,
-            CoreMatchers.nullValue()
-        )
+        assertNull(value.stringValue, "Nullable missing String value should be deserialized as null")
     }
 
     @Test
     fun testKotlinDeserialization_jsonNodeValue() {
-        assertThat(
-            "Nullable missing JsonNode value should be deserialized as null and not as NullNode",
+        assertNull(
             value.jsonNodeValue,
-            CoreMatchers.nullValue()
+            "Nullable missing JsonNode value should be deserialized as null and not as NullNode"
         )
     }
 
     @Test
     fun testKotlinDeserialization_jsonNodeValueProvidedNull() {
-        assertThat(
-            "Nullable JsonNode value provided as null should be deserialized as NullNode",
+        assertEquals(
+            NullNode.instance,
             value.jsonNodeValueProvidedNull,
-            CoreMatchers.equalTo(NullNode.instance)
+            "Nullable JsonNode value provided as null should be deserialized as NullNode"
         )
     }
 
     @Test
     fun testKotlinDeserialization_jsonNodeValueWithNullAsDefault() {
-        assertThat(
-            "Nullable by default missing JsonNode value should be deserialized as null and not as NullNode",
+        assertNull(
             value.jsonNodeValueWithNullAsDefault,
-            CoreMatchers.nullValue()
+            "Nullable by default missing JsonNode value should be deserialized as null and not as NullNode"
         )
     }
 
     @Test
     fun testKotlinDeserialization_jsonNodeValueWithNullAsDefaultProvidedNull() {
-        assertThat(
-            "Nullable by default JsonNode with provided null value in payload should be deserialized as NullNode",
+        assertEquals(
+            NullNode.instance,
             value.jsonNodeValueWithNullAsDefaultProvidedNull,
-            CoreMatchers.equalTo(NullNode.instance)
+            "Nullable by default JsonNode with provided null value in payload should be deserialized as NullNode"
         )
     }
 }