added more sum tests

Author: Jolanrensen

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/statistics/sum.kt

@@ -1,13 +1,18 @@
 package org.jetbrains.kotlinx.dataframe.statistics
 
 import io.kotest.assertions.throwables.shouldThrow
+import io.kotest.matchers.booleans.shouldBeTrue
+import io.kotest.matchers.doubles.shouldBeNaN
+import io.kotest.matchers.floats.shouldBeNaN
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.string.shouldContain
 import org.jetbrains.kotlinx.dataframe.api.columnOf
 import org.jetbrains.kotlinx.dataframe.api.dataFrameOf
 import org.jetbrains.kotlinx.dataframe.api.isEmpty
 import org.jetbrains.kotlinx.dataframe.api.rowSum
+import org.jetbrains.kotlinx.dataframe.api.rowSumOf
 import org.jetbrains.kotlinx.dataframe.api.sum
+import org.jetbrains.kotlinx.dataframe.api.sumFor
 import org.jetbrains.kotlinx.dataframe.api.sumOf
 import org.jetbrains.kotlinx.dataframe.api.toDataFrame
 import org.junit.Test
@@ -106,4 +111,75 @@ class SumTests {
             columnOf<Number>(1.0, 2, 3.0.toBigDecimal()).toDataFrame().sum()[0]
         }.message?.lowercase() shouldContain "primitive"
     }
+
+    @Test
+    fun `test skipNaN with float column`() {
+        val value by columnOf(1.0f, 2.0f, Float.NaN, 3.0f)
+        val df = dataFrameOf(value)
+
+        // With skipNaN = true (default is false)
+        value.sum(skipNaN = true) shouldBe 6.0f
+        df[value].sum(skipNaN = true) shouldBe 6.0f
+        df.sum(skipNaN = true)[value] shouldBe 6.0f
+        df.sumOf(skipNaN = true) { value().toInt() } shouldBe 6
+
+        // With skipNaN = false (default)
+        value.sum().shouldBeNaN()
+        df[value].sum().shouldBeNaN()
+        df.sum()[value].shouldBeNaN()
+        df.sumOf { value().toDouble() }.shouldBeNaN()
+    }
+
+    @Test
+    fun `test skipNaN with double column`() {
+        val value by columnOf(1.0, 2.0, Double.NaN, 3.0)
+        val df = dataFrameOf(value)
+
+        // With skipNaN = true (default is false)
+        value.sum(skipNaN = true) shouldBe 6.0
+        df[value].sum(skipNaN = true) shouldBe 6.0
+        df.sum(skipNaN = true)[value] shouldBe 6.0
+        df.sumOf(skipNaN = true) { value().toLong() } shouldBe 6L
+
+        // With skipNaN = false (default)
+        value.sum().shouldBeNaN()
+        df[value].sum().shouldBeNaN()
+        df.sum()[value].shouldBeNaN()
+        df.sumOf { value().toFloat() }.shouldBeNaN()
+    }
+
+    @Test
+    fun `test rowSum with skipNaN`() {
+        val row1 = dataFrameOf("a", "b", "c")(1.0, 2.0, 3.0)[0]
+        val row2 = dataFrameOf("a", "b", "c")(1.0, Double.NaN, 3)[0]
+
+        // With skipNaN = true
+        row1.rowSum(skipNaN = true) shouldBe 6.0
+        row2.rowSum(skipNaN = true) shouldBe 4.0
+
+        // With skipNaN = false (default)
+        row1.rowSum() shouldBe 6.0
+        (row2.rowSum() as Double).isNaN().shouldBeTrue()
+
+        // Test rowSumOf
+        row1.rowSumOf<Double?>(skipNaN = true) shouldBe 6.0
+        row2.rowSumOf<Double?>(skipNaN = true) shouldBe 1.0
+        row1.rowSumOf<Double?>() shouldBe 6.0
+        row2.rowSumOf<Double?>().shouldBeNaN()
+    }
+
+    @Test
+    fun `test sumFor with skipNaN`() {
+        val value1 by columnOf(1.0, 2.0, 3.0)
+        val value2 by columnOf<Number>(4.0, Float.NaN, 6)
+        val df = dataFrameOf(value1, value2)
+
+        // With skipNaN = true
+        df.sumFor(skipNaN = true) { value1 and value2 }[value1] shouldBe 6.0
+        df.sumFor(skipNaN = true) { value1 and value2 }[value2] shouldBe 10.0
+
+        // With skipNaN = false (default)
+        df.sumFor { value1 and value2 }[value1] shouldBe 6.0
+        (df.sumFor { value1 and value2 }[value2] as Double).shouldBeNaN()
+    }
 }