Merge pull request #758 from Kotlin/value-counts-test

Add a test for valueCounts

Author: koperagen

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataColumnTests.kt

@@ -1,10 +1,13 @@
 package org.jetbrains.kotlinx.dataframe.testSets.person
 
 import io.kotest.matchers.shouldBe
+import org.jetbrains.kotlinx.dataframe.api.columnOf
+import org.jetbrains.kotlinx.dataframe.api.count
 import org.jetbrains.kotlinx.dataframe.api.sort
 import org.jetbrains.kotlinx.dataframe.api.sortBy
 import org.jetbrains.kotlinx.dataframe.api.sortByDesc
 import org.jetbrains.kotlinx.dataframe.api.sortDesc
+import org.jetbrains.kotlinx.dataframe.api.valueCounts
 import org.junit.Test
 
 class DataColumnTests : BaseTest() {
@@ -14,4 +17,12 @@ class DataColumnTests : BaseTest() {
         typed.age.sort() shouldBe typed.sortBy { age }.age
         typed.age.sortDesc() shouldBe typed.sortByDesc { age }.age
     }
+
+    @Test
+    fun `value counts`() {
+        val languages by columnOf("Kotlin", "Kotlin", null, null, "C++")
+        val languageCounts = languages.valueCounts()
+        languageCounts[languages].values() shouldBe listOf("Kotlin", "C++")
+        languageCounts.count.values() shouldBe listOf(2, 1)
+    }
 }