tests: Do not rely on Kotlin JVM impl in sort tests

Some sort tests had an order of equal objects in a sorted list
hardcoded. It caused failures because an approach to placing
equal objects differs in Kotlin JVM and Kotlin Native sort
implementations. With this patch we check if all objects in a list
are sorted istead of checking an exact order of them.

backend.native/tests/external/stdlib/collections/CollectionTest/sortByInPlace.kt

@@ -1,14 +1,41 @@
 import kotlin.test.*
-import kotlin.comparisons.*
+
+fun <T: Comparable<T>> assertSorted(list: List<out T>, message: String = "") = assertSorted(list, message, { it })
+
+inline fun <T, R : Comparable<R>> assertSorted(list: List<out T>, message: String = "", crossinline selector: (T) -> R) {
+    if (list.isEmpty() || list.size == 1) {
+        return
+    }
+    val it = list.iterator()
+    var prev = selector(it.next())
+    while(it.hasNext()) {
+        val cur = selector(it.next())
+        assertTrue(prev.compareTo(cur) <= 0, message)
+        prev = cur
+    }
+}
+
+inline fun <T, R : Comparable<R>> assertSortedDescending(list: List<out T>, message: String = "", crossinline selector: (T) -> R) {
+    if (list.isEmpty() || list.size == 1) {
+        return
+    }
+    val it = list.iterator()
+    var prev = selector(it.next())
+    while(it.hasNext()) {
+        val cur = selector(it.next())
+        assertTrue(prev.compareTo(cur) >= 0, message)
+        prev = cur
+    }
+}
 
 fun box() {
     val data = arrayListOf("aa" to 20, "ab" to 3, "aa" to 3)
     data.sortBy { it.second }
-    assertEquals(listOf("ab" to 3, "aa" to 3, "aa" to 20), data)
+    assertSorted(data) { it.second }
 
     data.sortBy { it.first }
-    assertEquals(listOf("aa" to 3, "aa" to 20, "ab" to 3), data)
+    assertSorted(data) { it.first }
 
     data.sortByDescending { (it.first + it.second).length }
-    assertEquals(listOf("aa" to 20, "aa" to 3, "ab" to 3), data)
+    assertSortedDescending(data) { (it.first + it.second).length }
 }

backend.native/tests/external/stdlib/collections/CollectionTest/sortedNullableBy.kt

@@ -1,11 +1,27 @@
 import kotlin.test.*
 import kotlin.comparisons.*
 
+fun <T> assertSorted(list: List<T>, cmp: Comparator<in T>, message: String = "") {
+    if (list.isEmpty() || list.size == 1) {
+        return
+    }
+    val it = list.iterator()
+    var prev = it.next()
+    while(it.hasNext()) {
+        val cur = it.next()
+        assert(cmp.compare(prev, cur) <= 0)
+        prev = cur
+    }
+}
+
 fun box() {
     fun String.nullIfEmpty() = if (isEmpty()) null else this
     listOf(null, "", "a").let {
-        expect(listOf(null, "", "a")) { it.sortedWith(nullsFirst(compareBy { it })) }
-        expect(listOf("a", "", null)) { it.sortedWith(nullsLast(compareByDescending { it })) }
-        expect(listOf(null, "a", "")) { it.sortedWith(nullsFirst(compareByDescending { it.nullIfEmpty() })) }
+        assertSorted(it.sortedWith(nullsFirst(compareBy { it })), nullsFirst(compareBy { it }))
+        assertSorted(it.sortedWith(nullsLast(compareByDescending { it })), compareByDescending { it })
+        assertSorted(
+                it.sortedWith(nullsFirst(compareByDescending { it.nullIfEmpty() })),
+                nullsFirst(compareByDescending { it.nullIfEmpty() })
+        )
     }
 }