added tests for fillNulls and fillNA updates

Author: Jolanrensen

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/update.kt

@@ -2,6 +2,7 @@ package org.jetbrains.kotlinx.dataframe.api
 
 import io.kotest.matchers.shouldBe
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
 import org.junit.Test
 
 class UpdateTests {
@@ -12,4 +13,32 @@ class UpdateTests {
         val col by column<Int>()
         df.update { col }.with { 2 } shouldBe df
     }
+
+    @DataSchema
+    interface SchemaA {
+        val i: Int?
+    }
+
+    @DataSchema
+    interface SchemaB {
+        val i: Int
+    }
+
+    @Test
+    fun `fillNulls update`() {
+        val df = dataFrameOf("i")(1, null)
+
+        df.fillNulls(SchemaA::i).with { 42 }
+
+        df.fillNulls(SchemaB::i).with { 42 }
+    }
+
+    @Test
+    fun `fillNA update`() {
+        val df = dataFrameOf("i")(1, null)
+
+        df.fillNA(SchemaA::i).with { 42 }
+
+        df.fillNA(SchemaB::i).with { 42 }
+    }
 }